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| author | Adam Turner <9087854+AA-Turner@users.noreply.github.com> | 2025-01-21 23:28:32 +0000 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2025-01-21 23:28:32 +0000 |
| commit | 01bcf13a1c5bfca5124cf2e0679c9d1b25b04708 (patch) | |
| tree | 2ea805ee8c39d031de595c5d7d8629e0f4c42c82 /Lib/pydoc_data/topics.py | |
| parent | 29caec62ee0650493c83c778ee2ea50b0501bc41 (diff) | |
| download | cpython-01bcf13a1c5bfca5124cf2e0679c9d1b25b04708.tar.gz cpython-01bcf13a1c5bfca5124cf2e0679c9d1b25b04708.zip | |
GH-121970: Extract ``pydoc_topics`` into a new extension (#129116)
Diffstat (limited to 'Lib/pydoc_data/topics.py')
| -rw-r--r-- | Lib/pydoc_data/topics.py | 30264 |
1 files changed, 12780 insertions, 17484 deletions
diff --git a/Lib/pydoc_data/topics.py b/Lib/pydoc_data/topics.py index 97fed45d5a9..3e8c7ce321e 100644 --- a/Lib/pydoc_data/topics.py +++ b/Lib/pydoc_data/topics.py @@ -1,17485 +1,12781 @@ -# -*- coding: utf-8 -*- -# Autogenerated by Sphinx on Tue Jan 14 13:41:56 2025 +# Autogenerated by Sphinx on Tue Jan 21 03:33:33 2025 # as part of the release process. -topics = {'assert': 'The "assert" statement\n' - '**********************\n' - '\n' - 'Assert statements are a convenient way to insert debugging ' - 'assertions\n' - 'into a program:\n' - '\n' - ' assert_stmt ::= "assert" expression ["," expression]\n' - '\n' - 'The simple form, "assert expression", is equivalent to\n' - '\n' - ' if __debug__:\n' - ' if not expression: raise AssertionError\n' - '\n' - 'The extended form, "assert expression1, expression2", is ' - 'equivalent to\n' - '\n' - ' if __debug__:\n' - ' if not expression1: raise AssertionError(expression2)\n' - '\n' - 'These equivalences assume that "__debug__" and "AssertionError" ' - 'refer\n' - 'to the built-in variables with those names. In the current\n' - 'implementation, the built-in variable "__debug__" is "True" under\n' - 'normal circumstances, "False" when optimization is requested ' - '(command\n' - 'line option "-O"). The current code generator emits no code for ' - 'an\n' - '"assert" statement when optimization is requested at compile ' - 'time.\n' - 'Note that it is unnecessary to include the source code for the\n' - 'expression that failed in the error message; it will be displayed ' - 'as\n' - 'part of the stack trace.\n' - '\n' - 'Assignments to "__debug__" are illegal. The value for the ' - 'built-in\n' - 'variable is determined when the interpreter starts.\n', - 'assignment': 'Assignment statements\n' - '*********************\n' - '\n' - 'Assignment statements are used to (re)bind names to values and ' - 'to\n' - 'modify attributes or items of mutable objects:\n' - '\n' - ' assignment_stmt ::= (target_list "=")+ (starred_expression ' - '| yield_expression)\n' - ' target_list ::= target ("," target)* [","]\n' - ' target ::= identifier\n' - ' | "(" [target_list] ")"\n' - ' | "[" [target_list] "]"\n' - ' | attributeref\n' - ' | subscription\n' - ' | slicing\n' - ' | "*" target\n' - '\n' - '(See section Primaries for the syntax definitions for ' - '*attributeref*,\n' - '*subscription*, and *slicing*.)\n' - '\n' - 'An assignment statement evaluates the expression list ' - '(remember that\n' - 'this can be a single expression or a comma-separated list, the ' - 'latter\n' - 'yielding a tuple) and assigns the single resulting object to ' - 'each of\n' - 'the target lists, from left to right.\n' - '\n' - 'Assignment is defined recursively depending on the form of the ' - 'target\n' - '(list). When a target is part of a mutable object (an ' - 'attribute\n' - 'reference, subscription or slicing), the mutable object must\n' - 'ultimately perform the assignment and decide about its ' - 'validity, and\n' - 'may raise an exception if the assignment is unacceptable. The ' - 'rules\n' - 'observed by various types and the exceptions raised are given ' - 'with the\n' - 'definition of the object types (see section The standard type\n' - 'hierarchy).\n' - '\n' - 'Assignment of an object to a target list, optionally enclosed ' - 'in\n' - 'parentheses or square brackets, is recursively defined as ' - 'follows.\n' - '\n' - '* If the target list is a single target with no trailing ' - 'comma,\n' - ' optionally in parentheses, the object is assigned to that ' - 'target.\n' - '\n' - '* Else:\n' - '\n' - ' * If the target list contains one target prefixed with an ' - 'asterisk,\n' - ' called a “starred” target: The object must be an iterable ' - 'with at\n' - ' least as many items as there are targets in the target ' - 'list, minus\n' - ' one. The first items of the iterable are assigned, from ' - 'left to\n' - ' right, to the targets before the starred target. The ' - 'final items\n' - ' of the iterable are assigned to the targets after the ' - 'starred\n' - ' target. A list of the remaining items in the iterable is ' - 'then\n' - ' assigned to the starred target (the list can be empty).\n' - '\n' - ' * Else: The object must be an iterable with the same number ' - 'of items\n' - ' as there are targets in the target list, and the items ' - 'are\n' - ' assigned, from left to right, to the corresponding ' - 'targets.\n' - '\n' - 'Assignment of an object to a single target is recursively ' - 'defined as\n' - 'follows.\n' - '\n' - '* If the target is an identifier (name):\n' - '\n' - ' * If the name does not occur in a "global" or "nonlocal" ' - 'statement\n' - ' in the current code block: the name is bound to the object ' - 'in the\n' - ' current local namespace.\n' - '\n' - ' * Otherwise: the name is bound to the object in the global ' - 'namespace\n' - ' or the outer namespace determined by "nonlocal", ' - 'respectively.\n' - '\n' - ' The name is rebound if it was already bound. This may cause ' - 'the\n' - ' reference count for the object previously bound to the name ' - 'to reach\n' - ' zero, causing the object to be deallocated and its ' - 'destructor (if it\n' - ' has one) to be called.\n' - '\n' - '* If the target is an attribute reference: The primary ' - 'expression in\n' - ' the reference is evaluated. It should yield an object with\n' - ' assignable attributes; if this is not the case, "TypeError" ' - 'is\n' - ' raised. That object is then asked to assign the assigned ' - 'object to\n' - ' the given attribute; if it cannot perform the assignment, it ' - 'raises\n' - ' an exception (usually but not necessarily ' - '"AttributeError").\n' - '\n' - ' Note: If the object is a class instance and the attribute ' - 'reference\n' - ' occurs on both sides of the assignment operator, the ' - 'right-hand side\n' - ' expression, "a.x" can access either an instance attribute or ' - '(if no\n' - ' instance attribute exists) a class attribute. The left-hand ' - 'side\n' - ' target "a.x" is always set as an instance attribute, ' - 'creating it if\n' - ' necessary. Thus, the two occurrences of "a.x" do not ' - 'necessarily\n' - ' refer to the same attribute: if the right-hand side ' - 'expression\n' - ' refers to a class attribute, the left-hand side creates a ' - 'new\n' - ' instance attribute as the target of the assignment:\n' - '\n' - ' class Cls:\n' - ' x = 3 # class variable\n' - ' inst = Cls()\n' - ' inst.x = inst.x + 1 # writes inst.x as 4 leaving Cls.x ' - 'as 3\n' - '\n' - ' This description does not necessarily apply to descriptor\n' - ' attributes, such as properties created with "property()".\n' - '\n' - '* If the target is a subscription: The primary expression in ' - 'the\n' - ' reference is evaluated. It should yield either a mutable ' - 'sequence\n' - ' object (such as a list) or a mapping object (such as a ' - 'dictionary).\n' - ' Next, the subscript expression is evaluated.\n' - '\n' - ' If the primary is a mutable sequence object (such as a ' - 'list), the\n' - ' subscript must yield an integer. If it is negative, the ' - 'sequence’s\n' - ' length is added to it. The resulting value must be a ' - 'nonnegative\n' - ' integer less than the sequence’s length, and the sequence is ' - 'asked\n' - ' to assign the assigned object to its item with that index. ' - 'If the\n' - ' index is out of range, "IndexError" is raised (assignment to ' - 'a\n' - ' subscripted sequence cannot add new items to a list).\n' - '\n' - ' If the primary is a mapping object (such as a dictionary), ' - 'the\n' - ' subscript must have a type compatible with the mapping’s key ' - 'type,\n' - ' and the mapping is then asked to create a key/value pair ' - 'which maps\n' - ' the subscript to the assigned object. This can either ' - 'replace an\n' - ' existing key/value pair with the same key value, or insert a ' - 'new\n' - ' key/value pair (if no key with the same value existed).\n' - '\n' - ' For user-defined objects, the "__setitem__()" method is ' - 'called with\n' - ' appropriate arguments.\n' - '\n' - '* If the target is a slicing: The primary expression in the ' - 'reference\n' - ' is evaluated. It should yield a mutable sequence object ' - '(such as a\n' - ' list). The assigned object should be a sequence object of ' - 'the same\n' - ' type. Next, the lower and upper bound expressions are ' - 'evaluated,\n' - ' insofar they are present; defaults are zero and the ' - 'sequence’s\n' - ' length. The bounds should evaluate to integers. If either ' - 'bound is\n' - ' negative, the sequence’s length is added to it. The ' - 'resulting\n' - ' bounds are clipped to lie between zero and the sequence’s ' - 'length,\n' - ' inclusive. Finally, the sequence object is asked to replace ' - 'the\n' - ' slice with the items of the assigned sequence. The length ' - 'of the\n' - ' slice may be different from the length of the assigned ' - 'sequence,\n' - ' thus changing the length of the target sequence, if the ' - 'target\n' - ' sequence allows it.\n' - '\n' - '**CPython implementation detail:** In the current ' - 'implementation, the\n' - 'syntax for targets is taken to be the same as for expressions, ' - 'and\n' - 'invalid syntax is rejected during the code generation phase, ' - 'causing\n' - 'less detailed error messages.\n' - '\n' - 'Although the definition of assignment implies that overlaps ' - 'between\n' - 'the left-hand side and the right-hand side are ‘simultaneous’ ' - '(for\n' - 'example "a, b = b, a" swaps two variables), overlaps *within* ' - 'the\n' - 'collection of assigned-to variables occur left-to-right, ' - 'sometimes\n' - 'resulting in confusion. For instance, the following program ' - 'prints\n' - '"[0, 2]":\n' - '\n' - ' x = [0, 1]\n' - ' i = 0\n' - ' i, x[i] = 1, 2 # i is updated, then x[i] is ' - 'updated\n' - ' print(x)\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3132** - Extended Iterable Unpacking\n' - ' The specification for the "*target" feature.\n' - '\n' - '\n' - 'Augmented assignment statements\n' - '===============================\n' - '\n' - 'Augmented assignment is the combination, in a single ' - 'statement, of a\n' - 'binary operation and an assignment statement:\n' - '\n' - ' augmented_assignment_stmt ::= augtarget augop ' - '(expression_list | yield_expression)\n' - ' augtarget ::= identifier | attributeref | ' - 'subscription | slicing\n' - ' augop ::= "+=" | "-=" | "*=" | "@=" | ' - '"/=" | "//=" | "%=" | "**="\n' - ' | ">>=" | "<<=" | "&=" | "^=" | "|="\n' - '\n' - '(See section Primaries for the syntax definitions of the last ' - 'three\n' - 'symbols.)\n' - '\n' - 'An augmented assignment evaluates the target (which, unlike ' - 'normal\n' - 'assignment statements, cannot be an unpacking) and the ' - 'expression\n' - 'list, performs the binary operation specific to the type of ' - 'assignment\n' - 'on the two operands, and assigns the result to the original ' - 'target.\n' - 'The target is only evaluated once.\n' - '\n' - 'An augmented assignment statement like "x += 1" can be ' - 'rewritten as "x\n' - '= x + 1" to achieve a similar, but not exactly equal effect. ' - 'In the\n' - 'augmented version, "x" is only evaluated once. Also, when ' - 'possible,\n' - 'the actual operation is performed *in-place*, meaning that ' - 'rather than\n' - 'creating a new object and assigning that to the target, the ' - 'old object\n' - 'is modified instead.\n' - '\n' - 'Unlike normal assignments, augmented assignments evaluate the ' - 'left-\n' - 'hand side *before* evaluating the right-hand side. For ' - 'example, "a[i]\n' - '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and ' - 'performs\n' - 'the addition, and lastly, it writes the result back to ' - '"a[i]".\n' - '\n' - 'With the exception of assigning to tuples and multiple targets ' - 'in a\n' - 'single statement, the assignment done by augmented assignment\n' - 'statements is handled the same way as normal assignments. ' - 'Similarly,\n' - 'with the exception of the possible *in-place* behavior, the ' - 'binary\n' - 'operation performed by augmented assignment is the same as the ' - 'normal\n' - 'binary operations.\n' - '\n' - 'For targets which are attribute references, the same caveat ' - 'about\n' - 'class and instance attributes applies as for regular ' - 'assignments.\n' - '\n' - '\n' - 'Annotated assignment statements\n' - '===============================\n' - '\n' - '*Annotation* assignment is the combination, in a single ' - 'statement, of\n' - 'a variable or attribute annotation and an optional assignment\n' - 'statement:\n' - '\n' - ' annotated_assignment_stmt ::= augtarget ":" expression\n' - ' ["=" (starred_expression | ' - 'yield_expression)]\n' - '\n' - 'The difference from normal Assignment statements is that only ' - 'a single\n' - 'target is allowed.\n' - '\n' - 'The assignment target is considered “simple” if it consists of ' - 'a\n' - 'single name that is not enclosed in parentheses. For simple ' - 'assignment\n' - 'targets, if in class or module scope, the annotations are ' - 'gathered in\n' - 'a lazily evaluated annotation scope. The annotations can be ' - 'evaluated\n' - 'using the "__annotations__" attribute of a class or module, or ' - 'using\n' - 'the facilities in the "annotationlib" module.\n' - '\n' - 'If the assignment target is not simple (an attribute, ' - 'subscript node,\n' - 'or parenthesized name), the annotation is never evaluated.\n' - '\n' - 'If a name is annotated in a function scope, then this name is ' - 'local\n' - 'for that scope. Annotations are never evaluated and stored in ' - 'function\n' - 'scopes.\n' - '\n' - 'If the right hand side is present, an annotated assignment ' - 'performs\n' - 'the actual assignment as if there was no annotation present. ' - 'If the\n' - 'right hand side is not present for an expression target, then ' - 'the\n' - 'interpreter evaluates the target except for the last ' - '"__setitem__()"\n' - 'or "__setattr__()" call.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 526** - Syntax for Variable Annotations\n' - ' The proposal that added syntax for annotating the types ' - 'of\n' - ' variables (including class variables and instance ' - 'variables),\n' - ' instead of expressing them through comments.\n' - '\n' - ' **PEP 484** - Type hints\n' - ' The proposal that added the "typing" module to provide a ' - 'standard\n' - ' syntax for type annotations that can be used in static ' - 'analysis\n' - ' tools and IDEs.\n' - '\n' - 'Changed in version 3.8: Now annotated assignments allow the ' - 'same\n' - 'expressions in the right hand side as regular assignments. ' - 'Previously,\n' - 'some expressions (like un-parenthesized tuple expressions) ' - 'caused a\n' - 'syntax error.\n' - '\n' - 'Changed in version 3.14: Annotations are now lazily evaluated ' - 'in a\n' - 'separate annotation scope. If the assignment target is not ' - 'simple,\n' - 'annotations are never evaluated.\n', - 'assignment-expressions': 'Assignment expressions\n' - '**********************\n' - '\n' - ' assignment_expression ::= [identifier ":="] ' - 'expression\n' - '\n' - 'An assignment expression (sometimes also called a ' - '“named expression”\n' - 'or “walrus”) assigns an "expression" to an ' - '"identifier", while also\n' - 'returning the value of the "expression".\n' - '\n' - 'One common use case is when handling matched ' - 'regular expressions:\n' - '\n' - ' if matching := pattern.search(data):\n' - ' do_something(matching)\n' - '\n' - 'Or, when processing a file stream in chunks:\n' - '\n' - ' while chunk := file.read(9000):\n' - ' process(chunk)\n' - '\n' - 'Assignment expressions must be surrounded by ' - 'parentheses when used as\n' - 'expression statements and when used as ' - 'sub-expressions in slicing,\n' - 'conditional, lambda, keyword-argument, and ' - 'comprehension-if\n' - 'expressions and in "assert", "with", and ' - '"assignment" statements. In\n' - 'all other places where they can be used, ' - 'parentheses are not required,\n' - 'including in "if" and "while" statements.\n' - '\n' - 'Added in version 3.8: See **PEP 572** for more ' - 'details about\n' - 'assignment expressions.\n', - 'async': 'Coroutines\n' - '**********\n' - '\n' - 'Added in version 3.5.\n' - '\n' - '\n' - 'Coroutine function definition\n' - '=============================\n' - '\n' - ' async_funcdef ::= [decorators] "async" "def" funcname "(" ' - '[parameter_list] ")"\n' - ' ["->" expression] ":" suite\n' - '\n' - 'Execution of Python coroutines can be suspended and resumed at ' - 'many\n' - 'points (see *coroutine*). "await" expressions, "async for" and ' - '"async\n' - 'with" can only be used in the body of a coroutine function.\n' - '\n' - 'Functions defined with "async def" syntax are always coroutine\n' - 'functions, even if they do not contain "await" or "async" ' - 'keywords.\n' - '\n' - 'It is a "SyntaxError" to use a "yield from" expression inside the ' - 'body\n' - 'of a coroutine function.\n' - '\n' - 'An example of a coroutine function:\n' - '\n' - ' async def func(param1, param2):\n' - ' do_stuff()\n' - ' await some_coroutine()\n' - '\n' - 'Changed in version 3.7: "await" and "async" are now keywords;\n' - 'previously they were only treated as such inside the body of a\n' - 'coroutine function.\n' - '\n' - '\n' - 'The "async for" statement\n' - '=========================\n' - '\n' - ' async_for_stmt ::= "async" for_stmt\n' - '\n' - 'An *asynchronous iterable* provides an "__aiter__" method that\n' - 'directly returns an *asynchronous iterator*, which can call\n' - 'asynchronous code in its "__anext__" method.\n' - '\n' - 'The "async for" statement allows convenient iteration over\n' - 'asynchronous iterables.\n' - '\n' - 'The following code:\n' - '\n' - ' async for TARGET in ITER:\n' - ' SUITE\n' - ' else:\n' - ' SUITE2\n' - '\n' - 'Is semantically equivalent to:\n' - '\n' - ' iter = (ITER)\n' - ' iter = type(iter).__aiter__(iter)\n' - ' running = True\n' - '\n' - ' while running:\n' - ' try:\n' - ' TARGET = await type(iter).__anext__(iter)\n' - ' except StopAsyncIteration:\n' - ' running = False\n' - ' else:\n' - ' SUITE\n' - ' else:\n' - ' SUITE2\n' - '\n' - 'See also "__aiter__()" and "__anext__()" for details.\n' - '\n' - 'It is a "SyntaxError" to use an "async for" statement outside the ' - 'body\n' - 'of a coroutine function.\n' - '\n' - '\n' - 'The "async with" statement\n' - '==========================\n' - '\n' - ' async_with_stmt ::= "async" with_stmt\n' - '\n' - 'An *asynchronous context manager* is a *context manager* that is ' - 'able\n' - 'to suspend execution in its *enter* and *exit* methods.\n' - '\n' - 'The following code:\n' - '\n' - ' async with EXPRESSION as TARGET:\n' - ' SUITE\n' - '\n' - 'is semantically equivalent to:\n' - '\n' - ' manager = (EXPRESSION)\n' - ' aenter = type(manager).__aenter__\n' - ' aexit = type(manager).__aexit__\n' - ' value = await aenter(manager)\n' - ' hit_except = False\n' - '\n' - ' try:\n' - ' TARGET = value\n' - ' SUITE\n' - ' except:\n' - ' hit_except = True\n' - ' if not await aexit(manager, *sys.exc_info()):\n' - ' raise\n' - ' finally:\n' - ' if not hit_except:\n' - ' await aexit(manager, None, None, None)\n' - '\n' - 'See also "__aenter__()" and "__aexit__()" for details.\n' - '\n' - 'It is a "SyntaxError" to use an "async with" statement outside the\n' - 'body of a coroutine function.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 492** - Coroutines with async and await syntax\n' - ' The proposal that made coroutines a proper standalone concept ' - 'in\n' - ' Python, and added supporting syntax.\n', - 'atom-identifiers': 'Identifiers (Names)\n' - '*******************\n' - '\n' - 'An identifier occurring as an atom is a name. See ' - 'section Identifiers\n' - 'and keywords for lexical definition and section Naming ' - 'and binding for\n' - 'documentation of naming and binding.\n' - '\n' - 'When the name is bound to an object, evaluation of the ' - 'atom yields\n' - 'that object. When a name is not bound, an attempt to ' - 'evaluate it\n' - 'raises a "NameError" exception.\n' - '\n' - '\n' - 'Private name mangling\n' - '=====================\n' - '\n' - 'When an identifier that textually occurs in a class ' - 'definition begins\n' - 'with two or more underscore characters and does not end ' - 'in two or more\n' - 'underscores, it is considered a *private name* of that ' - 'class.\n' - '\n' - 'See also: The class specifications.\n' - '\n' - 'More precisely, private names are transformed to a ' - 'longer form before\n' - 'code is generated for them. If the transformed name is ' - 'longer than\n' - '255 characters, implementation-defined truncation may ' - 'happen.\n' - '\n' - 'The transformation is independent of the syntactical ' - 'context in which\n' - 'the identifier is used but only the following private ' - 'identifiers are\n' - 'mangled:\n' - '\n' - '* Any name used as the name of a variable that is ' - 'assigned or read or\n' - ' any name of an attribute being accessed.\n' - '\n' - ' The "__name__" attribute of nested functions, classes, ' - 'and type\n' - ' aliases is however not mangled.\n' - '\n' - '* The name of imported modules, e.g., "__spam" in ' - '"import __spam". If\n' - ' the module is part of a package (i.e., its name ' - 'contains a dot), the\n' - ' name is *not* mangled, e.g., the "__foo" in "import ' - '__foo.bar" is\n' - ' not mangled.\n' - '\n' - '* The name of an imported member, e.g., "__f" in "from ' - 'spam import\n' - ' __f".\n' - '\n' - 'The transformation rule is defined as follows:\n' - '\n' - '* The class name, with leading underscores removed and a ' - 'single\n' - ' leading underscore inserted, is inserted in front of ' - 'the identifier,\n' - ' e.g., the identifier "__spam" occurring in a class ' - 'named "Foo",\n' - ' "_Foo" or "__Foo" is transformed to "_Foo__spam".\n' - '\n' - '* If the class name consists only of underscores, the ' - 'transformation\n' - ' is the identity, e.g., the identifier "__spam" ' - 'occurring in a class\n' - ' named "_" or "__" is left as is.\n', - 'atom-literals': 'Literals\n' - '********\n' - '\n' - 'Python supports string and bytes literals and various ' - 'numeric\n' - 'literals:\n' - '\n' - ' literal ::= stringliteral | bytesliteral\n' - ' | integer | floatnumber | imagnumber\n' - '\n' - 'Evaluation of a literal yields an object of the given type ' - '(string,\n' - 'bytes, integer, floating-point number, complex number) with ' - 'the given\n' - 'value. The value may be approximated in the case of ' - 'floating-point\n' - 'and imaginary (complex) literals. See section Literals for ' - 'details.\n' - '\n' - 'All literals correspond to immutable data types, and hence ' - 'the\n' - 'object’s identity is less important than its value. ' - 'Multiple\n' - 'evaluations of literals with the same value (either the ' - 'same\n' - 'occurrence in the program text or a different occurrence) ' - 'may obtain\n' - 'the same object or a different object with the same ' - 'value.\n', - 'attribute-access': 'Customizing attribute access\n' - '****************************\n' - '\n' - 'The following methods can be defined to customize the ' - 'meaning of\n' - 'attribute access (use of, assignment to, or deletion of ' - '"x.name") for\n' - 'class instances.\n' - '\n' - 'object.__getattr__(self, name)\n' - '\n' - ' Called when the default attribute access fails with ' - 'an\n' - ' "AttributeError" (either "__getattribute__()" raises ' - 'an\n' - ' "AttributeError" because *name* is not an instance ' - 'attribute or an\n' - ' attribute in the class tree for "self"; or ' - '"__get__()" of a *name*\n' - ' property raises "AttributeError"). This method ' - 'should either\n' - ' return the (computed) attribute value or raise an ' - '"AttributeError"\n' - ' exception. The "object" class itself does not provide ' - 'this method.\n' - '\n' - ' Note that if the attribute is found through the ' - 'normal mechanism,\n' - ' "__getattr__()" is not called. (This is an ' - 'intentional asymmetry\n' - ' between "__getattr__()" and "__setattr__()".) This is ' - 'done both for\n' - ' efficiency reasons and because otherwise ' - '"__getattr__()" would have\n' - ' no way to access other attributes of the instance. ' - 'Note that at\n' - ' least for instance variables, you can take total ' - 'control by not\n' - ' inserting any values in the instance attribute ' - 'dictionary (but\n' - ' instead inserting them in another object). See the\n' - ' "__getattribute__()" method below for a way to ' - 'actually get total\n' - ' control over attribute access.\n' - '\n' - 'object.__getattribute__(self, name)\n' - '\n' - ' Called unconditionally to implement attribute ' - 'accesses for\n' - ' instances of the class. If the class also defines ' - '"__getattr__()",\n' - ' the latter will not be called unless ' - '"__getattribute__()" either\n' - ' calls it explicitly or raises an "AttributeError". ' - 'This method\n' - ' should return the (computed) attribute value or raise ' - 'an\n' - ' "AttributeError" exception. In order to avoid ' - 'infinite recursion in\n' - ' this method, its implementation should always call ' - 'the base class\n' - ' method with the same name to access any attributes it ' - 'needs, for\n' - ' example, "object.__getattribute__(self, name)".\n' - '\n' - ' Note:\n' - '\n' - ' This method may still be bypassed when looking up ' - 'special methods\n' - ' as the result of implicit invocation via language ' - 'syntax or\n' - ' built-in functions. See Special method lookup.\n' - '\n' - ' For certain sensitive attribute accesses, raises an ' - 'auditing event\n' - ' "object.__getattr__" with arguments "obj" and ' - '"name".\n' - '\n' - 'object.__setattr__(self, name, value)\n' - '\n' - ' Called when an attribute assignment is attempted. ' - 'This is called\n' - ' instead of the normal mechanism (i.e. store the value ' - 'in the\n' - ' instance dictionary). *name* is the attribute name, ' - '*value* is the\n' - ' value to be assigned to it.\n' - '\n' - ' If "__setattr__()" wants to assign to an instance ' - 'attribute, it\n' - ' should call the base class method with the same name, ' - 'for example,\n' - ' "object.__setattr__(self, name, value)".\n' - '\n' - ' For certain sensitive attribute assignments, raises ' - 'an auditing\n' - ' event "object.__setattr__" with arguments "obj", ' - '"name", "value".\n' - '\n' - 'object.__delattr__(self, name)\n' - '\n' - ' Like "__setattr__()" but for attribute deletion ' - 'instead of\n' - ' assignment. This should only be implemented if "del ' - 'obj.name" is\n' - ' meaningful for the object.\n' - '\n' - ' For certain sensitive attribute deletions, raises an ' - 'auditing event\n' - ' "object.__delattr__" with arguments "obj" and ' - '"name".\n' - '\n' - 'object.__dir__(self)\n' - '\n' - ' Called when "dir()" is called on the object. An ' - 'iterable must be\n' - ' returned. "dir()" converts the returned iterable to a ' - 'list and\n' - ' sorts it.\n' - '\n' - '\n' - 'Customizing module attribute access\n' - '===================================\n' - '\n' - 'Special names "__getattr__" and "__dir__" can be also ' - 'used to\n' - 'customize access to module attributes. The "__getattr__" ' - 'function at\n' - 'the module level should accept one argument which is the ' - 'name of an\n' - 'attribute and return the computed value or raise an ' - '"AttributeError".\n' - 'If an attribute is not found on a module object through ' - 'the normal\n' - 'lookup, i.e. "object.__getattribute__()", then ' - '"__getattr__" is\n' - 'searched in the module "__dict__" before raising an ' - '"AttributeError".\n' - 'If found, it is called with the attribute name and the ' - 'result is\n' - 'returned.\n' - '\n' - 'The "__dir__" function should accept no arguments, and ' - 'return an\n' - 'iterable of strings that represents the names accessible ' - 'on module. If\n' - 'present, this function overrides the standard "dir()" ' - 'search on a\n' - 'module.\n' - '\n' - 'For a more fine grained customization of the module ' - 'behavior (setting\n' - 'attributes, properties, etc.), one can set the ' - '"__class__" attribute\n' - 'of a module object to a subclass of "types.ModuleType". ' - 'For example:\n' - '\n' - ' import sys\n' - ' from types import ModuleType\n' - '\n' - ' class VerboseModule(ModuleType):\n' - ' def __repr__(self):\n' - " return f'Verbose {self.__name__}'\n" - '\n' - ' def __setattr__(self, attr, value):\n' - " print(f'Setting {attr}...')\n" - ' super().__setattr__(attr, value)\n' - '\n' - ' sys.modules[__name__].__class__ = VerboseModule\n' - '\n' - 'Note:\n' - '\n' - ' Defining module "__getattr__" and setting module ' - '"__class__" only\n' - ' affect lookups made using the attribute access syntax ' - '– directly\n' - ' accessing the module globals (whether by code within ' - 'the module, or\n' - ' via a reference to the module’s globals dictionary) is ' - 'unaffected.\n' - '\n' - 'Changed in version 3.5: "__class__" module attribute is ' - 'now writable.\n' - '\n' - 'Added in version 3.7: "__getattr__" and "__dir__" module ' - 'attributes.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 562** - Module __getattr__ and __dir__\n' - ' Describes the "__getattr__" and "__dir__" functions ' - 'on modules.\n' - '\n' - '\n' - 'Implementing Descriptors\n' - '========================\n' - '\n' - 'The following methods only apply when an instance of the ' - 'class\n' - 'containing the method (a so-called *descriptor* class) ' - 'appears in an\n' - '*owner* class (the descriptor must be in either the ' - 'owner’s class\n' - 'dictionary or in the class dictionary for one of its ' - 'parents). In the\n' - 'examples below, “the attribute” refers to the attribute ' - 'whose name is\n' - 'the key of the property in the owner class’ "__dict__". ' - 'The "object"\n' - 'class itself does not implement any of these protocols.\n' - '\n' - 'object.__get__(self, instance, owner=None)\n' - '\n' - ' Called to get the attribute of the owner class (class ' - 'attribute\n' - ' access) or of an instance of that class (instance ' - 'attribute\n' - ' access). The optional *owner* argument is the owner ' - 'class, while\n' - ' *instance* is the instance that the attribute was ' - 'accessed through,\n' - ' or "None" when the attribute is accessed through the ' - '*owner*.\n' - '\n' - ' This method should return the computed attribute ' - 'value or raise an\n' - ' "AttributeError" exception.\n' - '\n' - ' **PEP 252** specifies that "__get__()" is callable ' - 'with one or two\n' - ' arguments. Python’s own built-in descriptors support ' - 'this\n' - ' specification; however, it is likely that some ' - 'third-party tools\n' - ' have descriptors that require both arguments. ' - 'Python’s own\n' - ' "__getattribute__()" implementation always passes in ' - 'both arguments\n' - ' whether they are required or not.\n' - '\n' - 'object.__set__(self, instance, value)\n' - '\n' - ' Called to set the attribute on an instance *instance* ' - 'of the owner\n' - ' class to a new value, *value*.\n' - '\n' - ' Note, adding "__set__()" or "__delete__()" changes ' - 'the kind of\n' - ' descriptor to a “data descriptor”. See Invoking ' - 'Descriptors for\n' - ' more details.\n' - '\n' - 'object.__delete__(self, instance)\n' - '\n' - ' Called to delete the attribute on an instance ' - '*instance* of the\n' - ' owner class.\n' - '\n' - 'Instances of descriptors may also have the ' - '"__objclass__" attribute\n' - 'present:\n' - '\n' - 'object.__objclass__\n' - '\n' - ' The attribute "__objclass__" is interpreted by the ' - '"inspect" module\n' - ' as specifying the class where this object was defined ' - '(setting this\n' - ' appropriately can assist in runtime introspection of ' - 'dynamic class\n' - ' attributes). For callables, it may indicate that an ' - 'instance of the\n' - ' given type (or a subclass) is expected or required as ' - 'the first\n' - ' positional argument (for example, CPython sets this ' - 'attribute for\n' - ' unbound methods that are implemented in C).\n' - '\n' - '\n' - 'Invoking Descriptors\n' - '====================\n' - '\n' - 'In general, a descriptor is an object attribute with ' - '“binding\n' - 'behavior”, one whose attribute access has been ' - 'overridden by methods\n' - 'in the descriptor protocol: "__get__()", "__set__()", ' - 'and\n' - '"__delete__()". If any of those methods are defined for ' - 'an object, it\n' - 'is said to be a descriptor.\n' - '\n' - 'The default behavior for attribute access is to get, ' - 'set, or delete\n' - 'the attribute from an object’s dictionary. For instance, ' - '"a.x" has a\n' - 'lookup chain starting with "a.__dict__[\'x\']", then\n' - '"type(a).__dict__[\'x\']", and continuing through the ' - 'base classes of\n' - '"type(a)" excluding metaclasses.\n' - '\n' - 'However, if the looked-up value is an object defining ' - 'one of the\n' - 'descriptor methods, then Python may override the default ' - 'behavior and\n' - 'invoke the descriptor method instead. Where this occurs ' - 'in the\n' - 'precedence chain depends on which descriptor methods ' - 'were defined and\n' - 'how they were called.\n' - '\n' - 'The starting point for descriptor invocation is a ' - 'binding, "a.x". How\n' - 'the arguments are assembled depends on "a":\n' - '\n' - 'Direct Call\n' - ' The simplest and least common call is when user code ' - 'directly\n' - ' invokes a descriptor method: "x.__get__(a)".\n' - '\n' - 'Instance Binding\n' - ' If binding to an object instance, "a.x" is ' - 'transformed into the\n' - ' call: "type(a).__dict__[\'x\'].__get__(a, type(a))".\n' - '\n' - 'Class Binding\n' - ' If binding to a class, "A.x" is transformed into the ' - 'call:\n' - ' "A.__dict__[\'x\'].__get__(None, A)".\n' - '\n' - 'Super Binding\n' - ' A dotted lookup such as "super(A, a).x" searches\n' - ' "a.__class__.__mro__" for a base class "B" following ' - '"A" and then\n' - ' returns "B.__dict__[\'x\'].__get__(a, A)". If not a ' - 'descriptor, "x"\n' - ' is returned unchanged.\n' - '\n' - 'For instance bindings, the precedence of descriptor ' - 'invocation depends\n' - 'on which descriptor methods are defined. A descriptor ' - 'can define any\n' - 'combination of "__get__()", "__set__()" and ' - '"__delete__()". If it\n' - 'does not define "__get__()", then accessing the ' - 'attribute will return\n' - 'the descriptor object itself unless there is a value in ' - 'the object’s\n' - 'instance dictionary. If the descriptor defines ' - '"__set__()" and/or\n' - '"__delete__()", it is a data descriptor; if it defines ' - 'neither, it is\n' - 'a non-data descriptor. Normally, data descriptors ' - 'define both\n' - '"__get__()" and "__set__()", while non-data descriptors ' - 'have just the\n' - '"__get__()" method. Data descriptors with "__get__()" ' - 'and "__set__()"\n' - '(and/or "__delete__()") defined always override a ' - 'redefinition in an\n' - 'instance dictionary. In contrast, non-data descriptors ' - 'can be\n' - 'overridden by instances.\n' - '\n' - 'Python methods (including those decorated with ' - '"@staticmethod" and\n' - '"@classmethod") are implemented as non-data ' - 'descriptors. Accordingly,\n' - 'instances can redefine and override methods. This ' - 'allows individual\n' - 'instances to acquire behaviors that differ from other ' - 'instances of the\n' - 'same class.\n' - '\n' - 'The "property()" function is implemented as a data ' - 'descriptor.\n' - 'Accordingly, instances cannot override the behavior of a ' - 'property.\n' - '\n' - '\n' - '__slots__\n' - '=========\n' - '\n' - '*__slots__* allow us to explicitly declare data members ' - '(like\n' - 'properties) and deny the creation of "__dict__" and ' - '*__weakref__*\n' - '(unless explicitly declared in *__slots__* or available ' - 'in a parent.)\n' - '\n' - 'The space saved over using "__dict__" can be ' - 'significant. Attribute\n' - 'lookup speed can be significantly improved as well.\n' - '\n' - 'object.__slots__\n' - '\n' - ' This class variable can be assigned a string, ' - 'iterable, or sequence\n' - ' of strings with variable names used by instances. ' - '*__slots__*\n' - ' reserves space for the declared variables and ' - 'prevents the\n' - ' automatic creation of "__dict__" and *__weakref__* ' - 'for each\n' - ' instance.\n' - '\n' - 'Notes on using *__slots__*:\n' - '\n' - '* When inheriting from a class without *__slots__*, the ' - '"__dict__" and\n' - ' *__weakref__* attribute of the instances will always ' - 'be accessible.\n' - '\n' - '* Without a "__dict__" variable, instances cannot be ' - 'assigned new\n' - ' variables not listed in the *__slots__* definition. ' - 'Attempts to\n' - ' assign to an unlisted variable name raises ' - '"AttributeError". If\n' - ' dynamic assignment of new variables is desired, then ' - 'add\n' - ' "\'__dict__\'" to the sequence of strings in the ' - '*__slots__*\n' - ' declaration.\n' - '\n' - '* Without a *__weakref__* variable for each instance, ' - 'classes defining\n' - ' *__slots__* do not support "weak references" to its ' - 'instances. If\n' - ' weak reference support is needed, then add ' - '"\'__weakref__\'" to the\n' - ' sequence of strings in the *__slots__* declaration.\n' - '\n' - '* *__slots__* are implemented at the class level by ' - 'creating\n' - ' descriptors for each variable name. As a result, ' - 'class attributes\n' - ' cannot be used to set default values for instance ' - 'variables defined\n' - ' by *__slots__*; otherwise, the class attribute would ' - 'overwrite the\n' - ' descriptor assignment.\n' - '\n' - '* The action of a *__slots__* declaration is not limited ' - 'to the class\n' - ' where it is defined. *__slots__* declared in parents ' - 'are available\n' - ' in child classes. However, instances of a child ' - 'subclass will get a\n' - ' "__dict__" and *__weakref__* unless the subclass also ' - 'defines\n' - ' *__slots__* (which should only contain names of any ' - '*additional*\n' - ' slots).\n' - '\n' - '* If a class defines a slot also defined in a base ' - 'class, the instance\n' - ' variable defined by the base class slot is ' - 'inaccessible (except by\n' - ' retrieving its descriptor directly from the base ' - 'class). This\n' - ' renders the meaning of the program undefined. In the ' - 'future, a\n' - ' check may be added to prevent this.\n' - '\n' - '* "TypeError" will be raised if nonempty *__slots__* are ' - 'defined for a\n' - ' class derived from a ""variable-length" built-in type" ' - 'such as\n' - ' "int", "bytes", and "tuple".\n' - '\n' - '* Any non-string *iterable* may be assigned to ' - '*__slots__*.\n' - '\n' - '* If a "dictionary" is used to assign *__slots__*, the ' - 'dictionary keys\n' - ' will be used as the slot names. The values of the ' - 'dictionary can be\n' - ' used to provide per-attribute docstrings that will be ' - 'recognised by\n' - ' "inspect.getdoc()" and displayed in the output of ' - '"help()".\n' - '\n' - '* "__class__" assignment works only if both classes have ' - 'the same\n' - ' *__slots__*.\n' - '\n' - '* Multiple inheritance with multiple slotted parent ' - 'classes can be\n' - ' used, but only one parent is allowed to have ' - 'attributes created by\n' - ' slots (the other bases must have empty slot layouts) - ' - 'violations\n' - ' raise "TypeError".\n' - '\n' - '* If an *iterator* is used for *__slots__* then a ' - '*descriptor* is\n' - ' created for each of the iterator’s values. However, ' - 'the *__slots__*\n' - ' attribute will be an empty iterator.\n', - 'attribute-references': 'Attribute references\n' - '********************\n' - '\n' - 'An attribute reference is a primary followed by a ' - 'period and a name:\n' - '\n' - ' attributeref ::= primary "." identifier\n' - '\n' - 'The primary must evaluate to an object of a type ' - 'that supports\n' - 'attribute references, which most objects do. This ' - 'object is then\n' - 'asked to produce the attribute whose name is the ' - 'identifier. The type\n' - 'and value produced is determined by the object. ' - 'Multiple evaluations\n' - 'of the same attribute reference may yield different ' - 'objects.\n' - '\n' - 'This production can be customized by overriding the\n' - '"__getattribute__()" method or the "__getattr__()" ' - 'method. The\n' - '"__getattribute__()" method is called first and ' - 'either returns a value\n' - 'or raises "AttributeError" if the attribute is not ' - 'available.\n' - '\n' - 'If an "AttributeError" is raised and the object has ' - 'a "__getattr__()"\n' - 'method, that method is called as a fallback.\n', - 'augassign': 'Augmented assignment statements\n' - '*******************************\n' - '\n' - 'Augmented assignment is the combination, in a single statement, ' - 'of a\n' - 'binary operation and an assignment statement:\n' - '\n' - ' augmented_assignment_stmt ::= augtarget augop ' - '(expression_list | yield_expression)\n' - ' augtarget ::= identifier | attributeref | ' - 'subscription | slicing\n' - ' augop ::= "+=" | "-=" | "*=" | "@=" | ' - '"/=" | "//=" | "%=" | "**="\n' - ' | ">>=" | "<<=" | "&=" | "^=" | "|="\n' - '\n' - '(See section Primaries for the syntax definitions of the last ' - 'three\n' - 'symbols.)\n' - '\n' - 'An augmented assignment evaluates the target (which, unlike ' - 'normal\n' - 'assignment statements, cannot be an unpacking) and the ' - 'expression\n' - 'list, performs the binary operation specific to the type of ' - 'assignment\n' - 'on the two operands, and assigns the result to the original ' - 'target.\n' - 'The target is only evaluated once.\n' - '\n' - 'An augmented assignment statement like "x += 1" can be ' - 'rewritten as "x\n' - '= x + 1" to achieve a similar, but not exactly equal effect. In ' - 'the\n' - 'augmented version, "x" is only evaluated once. Also, when ' - 'possible,\n' - 'the actual operation is performed *in-place*, meaning that ' - 'rather than\n' - 'creating a new object and assigning that to the target, the old ' - 'object\n' - 'is modified instead.\n' - '\n' - 'Unlike normal assignments, augmented assignments evaluate the ' - 'left-\n' - 'hand side *before* evaluating the right-hand side. For ' - 'example, "a[i]\n' - '+= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and ' - 'performs\n' - 'the addition, and lastly, it writes the result back to "a[i]".\n' - '\n' - 'With the exception of assigning to tuples and multiple targets ' - 'in a\n' - 'single statement, the assignment done by augmented assignment\n' - 'statements is handled the same way as normal assignments. ' - 'Similarly,\n' - 'with the exception of the possible *in-place* behavior, the ' - 'binary\n' - 'operation performed by augmented assignment is the same as the ' - 'normal\n' - 'binary operations.\n' - '\n' - 'For targets which are attribute references, the same caveat ' - 'about\n' - 'class and instance attributes applies as for regular ' - 'assignments.\n', - 'await': 'Await expression\n' - '****************\n' - '\n' - 'Suspend the execution of *coroutine* on an *awaitable* object. Can\n' - 'only be used inside a *coroutine function*.\n' - '\n' - ' await_expr ::= "await" primary\n' - '\n' - 'Added in version 3.5.\n', - 'binary': 'Binary arithmetic operations\n' - '****************************\n' - '\n' - 'The binary arithmetic operations have the conventional priority\n' - 'levels. Note that some of these operations also apply to certain ' - 'non-\n' - 'numeric types. Apart from the power operator, there are only two\n' - 'levels, one for multiplicative operators and one for additive\n' - 'operators:\n' - '\n' - ' m_expr ::= u_expr | m_expr "*" u_expr | m_expr "@" m_expr |\n' - ' m_expr "//" u_expr | m_expr "/" u_expr |\n' - ' m_expr "%" u_expr\n' - ' a_expr ::= m_expr | a_expr "+" m_expr | a_expr "-" m_expr\n' - '\n' - 'The "*" (multiplication) operator yields the product of its ' - 'arguments.\n' - 'The arguments must either both be numbers, or one argument must be ' - 'an\n' - 'integer and the other must be a sequence. In the former case, the\n' - 'numbers are converted to a common real type and then multiplied\n' - 'together. In the latter case, sequence repetition is performed; ' - 'a\n' - 'negative repetition factor yields an empty sequence.\n' - '\n' - 'This operation can be customized using the special "__mul__()" ' - 'and\n' - '"__rmul__()" methods.\n' - '\n' - 'Changed in version 3.14: If only one operand is a complex number, ' - 'the\n' - 'other operand is converted to a floating-point number.\n' - '\n' - 'The "@" (at) operator is intended to be used for matrix\n' - 'multiplication. No builtin Python types implement this operator.\n' - '\n' - 'This operation can be customized using the special "__matmul__()" ' - 'and\n' - '"__rmatmul__()" methods.\n' - '\n' - 'Added in version 3.5.\n' - '\n' - 'The "/" (division) and "//" (floor division) operators yield the\n' - 'quotient of their arguments. The numeric arguments are first\n' - 'converted to a common type. Division of integers yields a float, ' - 'while\n' - 'floor division of integers results in an integer; the result is ' - 'that\n' - 'of mathematical division with the ‘floor’ function applied to the\n' - 'result. Division by zero raises the "ZeroDivisionError" ' - 'exception.\n' - '\n' - 'The division operation can be customized using the special\n' - '"__truediv__()" and "__rtruediv__()" methods. The floor division\n' - 'operation can be customized using the special "__floordiv__()" ' - 'and\n' - '"__rfloordiv__()" methods.\n' - '\n' - 'The "%" (modulo) operator yields the remainder from the division ' - 'of\n' - 'the first argument by the second. The numeric arguments are ' - 'first\n' - 'converted to a common type. A zero right argument raises the\n' - '"ZeroDivisionError" exception. The arguments may be ' - 'floating-point\n' - 'numbers, e.g., "3.14%0.7" equals "0.34" (since "3.14" equals ' - '"4*0.7 +\n' - '0.34".) The modulo operator always yields a result with the same ' - 'sign\n' - 'as its second operand (or zero); the absolute value of the result ' - 'is\n' - 'strictly smaller than the absolute value of the second operand ' - '[1].\n' - '\n' - 'The floor division and modulo operators are connected by the ' - 'following\n' - 'identity: "x == (x//y)*y + (x%y)". Floor division and modulo are ' - 'also\n' - 'connected with the built-in function "divmod()": "divmod(x, y) ==\n' - '(x//y, x%y)". [2].\n' - '\n' - 'In addition to performing the modulo operation on numbers, the ' - '"%"\n' - 'operator is also overloaded by string objects to perform ' - 'old-style\n' - 'string formatting (also known as interpolation). The syntax for\n' - 'string formatting is described in the Python Library Reference,\n' - 'section printf-style String Formatting.\n' - '\n' - 'The *modulo* operation can be customized using the special ' - '"__mod__()"\n' - 'and "__rmod__()" methods.\n' - '\n' - 'The floor division operator, the modulo operator, and the ' - '"divmod()"\n' - 'function are not defined for complex numbers. Instead, convert to ' - 'a\n' - 'floating-point number using the "abs()" function if appropriate.\n' - '\n' - 'The "+" (addition) operator yields the sum of its arguments. The\n' - 'arguments must either both be numbers or both be sequences of the ' - 'same\n' - 'type. In the former case, the numbers are converted to a common ' - 'real\n' - 'type and then added together. In the latter case, the sequences ' - 'are\n' - 'concatenated.\n' - '\n' - 'This operation can be customized using the special "__add__()" ' - 'and\n' - '"__radd__()" methods.\n' - '\n' - 'Changed in version 3.14: If only one operand is a complex number, ' - 'the\n' - 'other operand is converted to a floating-point number.\n' - '\n' - 'The "-" (subtraction) operator yields the difference of its ' - 'arguments.\n' - 'The numeric arguments are first converted to a common real type.\n' - '\n' - 'This operation can be customized using the special "__sub__()" ' - 'and\n' - '"__rsub__()" methods.\n' - '\n' - 'Changed in version 3.14: If only one operand is a complex number, ' - 'the\n' - 'other operand is converted to a floating-point number.\n', - 'bitwise': 'Binary bitwise operations\n' - '*************************\n' - '\n' - 'Each of the three bitwise operations has a different priority ' - 'level:\n' - '\n' - ' and_expr ::= shift_expr | and_expr "&" shift_expr\n' - ' xor_expr ::= and_expr | xor_expr "^" and_expr\n' - ' or_expr ::= xor_expr | or_expr "|" xor_expr\n' - '\n' - 'The "&" operator yields the bitwise AND of its arguments, which ' - 'must\n' - 'be integers or one of them must be a custom object overriding\n' - '"__and__()" or "__rand__()" special methods.\n' - '\n' - 'The "^" operator yields the bitwise XOR (exclusive OR) of its\n' - 'arguments, which must be integers or one of them must be a ' - 'custom\n' - 'object overriding "__xor__()" or "__rxor__()" special methods.\n' - '\n' - 'The "|" operator yields the bitwise (inclusive) OR of its ' - 'arguments,\n' - 'which must be integers or one of them must be a custom object\n' - 'overriding "__or__()" or "__ror__()" special methods.\n', - 'bltin-code-objects': 'Code Objects\n' - '************\n' - '\n' - 'Code objects are used by the implementation to ' - 'represent “pseudo-\n' - 'compiled” executable Python code such as a function ' - 'body. They differ\n' - 'from function objects because they don’t contain a ' - 'reference to their\n' - 'global execution environment. Code objects are ' - 'returned by the built-\n' - 'in "compile()" function and can be extracted from ' - 'function objects\n' - 'through their "__code__" attribute. See also the ' - '"code" module.\n' - '\n' - 'Accessing "__code__" raises an auditing event ' - '"object.__getattr__"\n' - 'with arguments "obj" and ""__code__"".\n' - '\n' - 'A code object can be executed or evaluated by passing ' - 'it (instead of a\n' - 'source string) to the "exec()" or "eval()" built-in ' - 'functions.\n' - '\n' - 'See The standard type hierarchy for more ' - 'information.\n', - 'bltin-ellipsis-object': 'The Ellipsis Object\n' - '*******************\n' - '\n' - 'This object is commonly used by slicing (see ' - 'Slicings). It supports\n' - 'no special operations. There is exactly one ' - 'ellipsis object, named\n' - '"Ellipsis" (a built-in name). "type(Ellipsis)()" ' - 'produces the\n' - '"Ellipsis" singleton.\n' - '\n' - 'It is written as "Ellipsis" or "...".\n', - 'bltin-null-object': 'The Null Object\n' - '***************\n' - '\n' - 'This object is returned by functions that don’t ' - 'explicitly return a\n' - 'value. It supports no special operations. There is ' - 'exactly one null\n' - 'object, named "None" (a built-in name). "type(None)()" ' - 'produces the\n' - 'same singleton.\n' - '\n' - 'It is written as "None".\n', - 'bltin-type-objects': 'Type Objects\n' - '************\n' - '\n' - 'Type objects represent the various object types. An ' - 'object’s type is\n' - 'accessed by the built-in function "type()". There are ' - 'no special\n' - 'operations on types. The standard module "types" ' - 'defines names for\n' - 'all standard built-in types.\n' - '\n' - 'Types are written like this: "<class \'int\'>".\n', - 'booleans': 'Boolean operations\n' - '******************\n' - '\n' - ' or_test ::= and_test | or_test "or" and_test\n' - ' and_test ::= not_test | and_test "and" not_test\n' - ' not_test ::= comparison | "not" not_test\n' - '\n' - 'In the context of Boolean operations, and also when expressions ' - 'are\n' - 'used by control flow statements, the following values are ' - 'interpreted\n' - 'as false: "False", "None", numeric zero of all types, and empty\n' - 'strings and containers (including strings, tuples, lists,\n' - 'dictionaries, sets and frozensets). All other values are ' - 'interpreted\n' - 'as true. User-defined objects can customize their truth value ' - 'by\n' - 'providing a "__bool__()" method.\n' - '\n' - 'The operator "not" yields "True" if its argument is false, ' - '"False"\n' - 'otherwise.\n' - '\n' - 'The expression "x and y" first evaluates *x*; if *x* is false, ' - 'its\n' - 'value is returned; otherwise, *y* is evaluated and the resulting ' - 'value\n' - 'is returned.\n' - '\n' - 'The expression "x or y" first evaluates *x*; if *x* is true, its ' - 'value\n' - 'is returned; otherwise, *y* is evaluated and the resulting value ' - 'is\n' - 'returned.\n' - '\n' - 'Note that neither "and" nor "or" restrict the value and type ' - 'they\n' - 'return to "False" and "True", but rather return the last ' - 'evaluated\n' - 'argument. This is sometimes useful, e.g., if "s" is a string ' - 'that\n' - 'should be replaced by a default value if it is empty, the ' - 'expression\n' - '"s or \'foo\'" yields the desired value. Because "not" has to ' - 'create a\n' - 'new value, it returns a boolean value regardless of the type of ' - 'its\n' - 'argument (for example, "not \'foo\'" produces "False" rather ' - 'than "\'\'".)\n', - 'break': 'The "break" statement\n' - '*********************\n' - '\n' - ' break_stmt ::= "break"\n' - '\n' - '"break" may only occur syntactically nested in a "for" or "while"\n' - 'loop, but not nested in a function or class definition within that\n' - 'loop.\n' - '\n' - 'It terminates the nearest enclosing loop, skipping the optional ' - '"else"\n' - 'clause if the loop has one.\n' - '\n' - 'If a "for" loop is terminated by "break", the loop control target\n' - 'keeps its current value.\n' - '\n' - 'When "break" passes control out of a "try" statement with a ' - '"finally"\n' - 'clause, that "finally" clause is executed before really leaving ' - 'the\n' - 'loop.\n', - 'callable-types': 'Emulating callable objects\n' - '**************************\n' - '\n' - 'object.__call__(self[, args...])\n' - '\n' - ' Called when the instance is “called” as a function; if ' - 'this method\n' - ' is defined, "x(arg1, arg2, ...)" roughly translates to\n' - ' "type(x).__call__(x, arg1, ...)". The "object" class ' - 'itself does\n' - ' not provide this method.\n', - 'calls': 'Calls\n' - '*****\n' - '\n' - 'A call calls a callable object (e.g., a *function*) with a ' - 'possibly\n' - 'empty series of *arguments*:\n' - '\n' - ' call ::= primary "(" [argument_list [","] | ' - 'comprehension] ")"\n' - ' argument_list ::= positional_arguments ["," ' - 'starred_and_keywords]\n' - ' ["," keywords_arguments]\n' - ' | starred_and_keywords ["," ' - 'keywords_arguments]\n' - ' | keywords_arguments\n' - ' positional_arguments ::= positional_item ("," positional_item)*\n' - ' positional_item ::= assignment_expression | "*" expression\n' - ' starred_and_keywords ::= ("*" expression | keyword_item)\n' - ' ("," "*" expression | "," ' - 'keyword_item)*\n' - ' keywords_arguments ::= (keyword_item | "**" expression)\n' - ' ("," keyword_item | "," "**" ' - 'expression)*\n' - ' keyword_item ::= identifier "=" expression\n' - '\n' - 'An optional trailing comma may be present after the positional and\n' - 'keyword arguments but does not affect the semantics.\n' - '\n' - 'The primary must evaluate to a callable object (user-defined\n' - 'functions, built-in functions, methods of built-in objects, class\n' - 'objects, methods of class instances, and all objects having a\n' - '"__call__()" method are callable). All argument expressions are\n' - 'evaluated before the call is attempted. Please refer to section\n' - 'Function definitions for the syntax of formal *parameter* lists.\n' - '\n' - 'If keyword arguments are present, they are first converted to\n' - 'positional arguments, as follows. First, a list of unfilled slots ' - 'is\n' - 'created for the formal parameters. If there are N positional\n' - 'arguments, they are placed in the first N slots. Next, for each\n' - 'keyword argument, the identifier is used to determine the\n' - 'corresponding slot (if the identifier is the same as the first ' - 'formal\n' - 'parameter name, the first slot is used, and so on). If the slot ' - 'is\n' - 'already filled, a "TypeError" exception is raised. Otherwise, the\n' - 'argument is placed in the slot, filling it (even if the expression ' - 'is\n' - '"None", it fills the slot). When all arguments have been ' - 'processed,\n' - 'the slots that are still unfilled are filled with the ' - 'corresponding\n' - 'default value from the function definition. (Default values are\n' - 'calculated, once, when the function is defined; thus, a mutable ' - 'object\n' - 'such as a list or dictionary used as default value will be shared ' - 'by\n' - 'all calls that don’t specify an argument value for the ' - 'corresponding\n' - 'slot; this should usually be avoided.) If there are any unfilled\n' - 'slots for which no default value is specified, a "TypeError" ' - 'exception\n' - 'is raised. Otherwise, the list of filled slots is used as the\n' - 'argument list for the call.\n' - '\n' - '**CPython implementation detail:** An implementation may provide\n' - 'built-in functions whose positional parameters do not have names, ' - 'even\n' - 'if they are ‘named’ for the purpose of documentation, and which\n' - 'therefore cannot be supplied by keyword. In CPython, this is the ' - 'case\n' - 'for functions implemented in C that use "PyArg_ParseTuple()" to ' - 'parse\n' - 'their arguments.\n' - '\n' - 'If there are more positional arguments than there are formal ' - 'parameter\n' - 'slots, a "TypeError" exception is raised, unless a formal ' - 'parameter\n' - 'using the syntax "*identifier" is present; in this case, that ' - 'formal\n' - 'parameter receives a tuple containing the excess positional ' - 'arguments\n' - '(or an empty tuple if there were no excess positional arguments).\n' - '\n' - 'If any keyword argument does not correspond to a formal parameter\n' - 'name, a "TypeError" exception is raised, unless a formal parameter\n' - 'using the syntax "**identifier" is present; in this case, that ' - 'formal\n' - 'parameter receives a dictionary containing the excess keyword\n' - 'arguments (using the keywords as keys and the argument values as\n' - 'corresponding values), or a (new) empty dictionary if there were ' - 'no\n' - 'excess keyword arguments.\n' - '\n' - 'If the syntax "*expression" appears in the function call, ' - '"expression"\n' - 'must evaluate to an *iterable*. Elements from these iterables are\n' - 'treated as if they were additional positional arguments. For the ' - 'call\n' - '"f(x1, x2, *y, x3, x4)", if *y* evaluates to a sequence *y1*, …, ' - '*yM*,\n' - 'this is equivalent to a call with M+4 positional arguments *x1*, ' - '*x2*,\n' - '*y1*, …, *yM*, *x3*, *x4*.\n' - '\n' - 'A consequence of this is that although the "*expression" syntax ' - 'may\n' - 'appear *after* explicit keyword arguments, it is processed ' - '*before*\n' - 'the keyword arguments (and any "**expression" arguments – see ' - 'below).\n' - 'So:\n' - '\n' - ' >>> def f(a, b):\n' - ' ... print(a, b)\n' - ' ...\n' - ' >>> f(b=1, *(2,))\n' - ' 2 1\n' - ' >>> f(a=1, *(2,))\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 1, in <module>\n' - " TypeError: f() got multiple values for keyword argument 'a'\n" - ' >>> f(1, *(2,))\n' - ' 1 2\n' - '\n' - 'It is unusual for both keyword arguments and the "*expression" ' - 'syntax\n' - 'to be used in the same call, so in practice this confusion does ' - 'not\n' - 'often arise.\n' - '\n' - 'If the syntax "**expression" appears in the function call,\n' - '"expression" must evaluate to a *mapping*, the contents of which ' - 'are\n' - 'treated as additional keyword arguments. If a parameter matching a ' - 'key\n' - 'has already been given a value (by an explicit keyword argument, ' - 'or\n' - 'from another unpacking), a "TypeError" exception is raised.\n' - '\n' - 'When "**expression" is used, each key in this mapping must be a\n' - 'string. Each value from the mapping is assigned to the first ' - 'formal\n' - 'parameter eligible for keyword assignment whose name is equal to ' - 'the\n' - 'key. A key need not be a Python identifier (e.g. ""max-temp °F"" ' - 'is\n' - 'acceptable, although it will not match any formal parameter that ' - 'could\n' - 'be declared). If there is no match to a formal parameter the ' - 'key-value\n' - 'pair is collected by the "**" parameter, if there is one, or if ' - 'there\n' - 'is not, a "TypeError" exception is raised.\n' - '\n' - 'Formal parameters using the syntax "*identifier" or "**identifier"\n' - 'cannot be used as positional argument slots or as keyword argument\n' - 'names.\n' - '\n' - 'Changed in version 3.5: Function calls accept any number of "*" ' - 'and\n' - '"**" unpackings, positional arguments may follow iterable ' - 'unpackings\n' - '("*"), and keyword arguments may follow dictionary unpackings ' - '("**").\n' - 'Originally proposed by **PEP 448**.\n' - '\n' - 'A call always returns some value, possibly "None", unless it raises ' - 'an\n' - 'exception. How this value is computed depends on the type of the\n' - 'callable object.\n' - '\n' - 'If it is—\n' - '\n' - 'a user-defined function:\n' - ' The code block for the function is executed, passing it the\n' - ' argument list. The first thing the code block will do is bind ' - 'the\n' - ' formal parameters to the arguments; this is described in ' - 'section\n' - ' Function definitions. When the code block executes a "return"\n' - ' statement, this specifies the return value of the function ' - 'call.\n' - ' If execution reaches the end of the code block without executing ' - 'a\n' - ' "return" statement, the return value is "None".\n' - '\n' - 'a built-in function or method:\n' - ' The result is up to the interpreter; see Built-in Functions for ' - 'the\n' - ' descriptions of built-in functions and methods.\n' - '\n' - 'a class object:\n' - ' A new instance of that class is returned.\n' - '\n' - 'a class instance method:\n' - ' The corresponding user-defined function is called, with an ' - 'argument\n' - ' list that is one longer than the argument list of the call: the\n' - ' instance becomes the first argument.\n' - '\n' - 'a class instance:\n' - ' The class must define a "__call__()" method; the effect is then ' - 'the\n' - ' same as if that method was called.\n', - 'class': 'Class definitions\n' - '*****************\n' - '\n' - 'A class definition defines a class object (see section The ' - 'standard\n' - 'type hierarchy):\n' - '\n' - ' classdef ::= [decorators] "class" classname [type_params] ' - '[inheritance] ":" suite\n' - ' inheritance ::= "(" [argument_list] ")"\n' - ' classname ::= identifier\n' - '\n' - 'A class definition is an executable statement. The inheritance ' - 'list\n' - 'usually gives a list of base classes (see Metaclasses for more\n' - 'advanced uses), so each item in the list should evaluate to a ' - 'class\n' - 'object which allows subclassing. Classes without an inheritance ' - 'list\n' - 'inherit, by default, from the base class "object"; hence,\n' - '\n' - ' class Foo:\n' - ' pass\n' - '\n' - 'is equivalent to\n' - '\n' - ' class Foo(object):\n' - ' pass\n' - '\n' - 'The class’s suite is then executed in a new execution frame (see\n' - 'Naming and binding), using a newly created local namespace and the\n' - 'original global namespace. (Usually, the suite contains mostly\n' - 'function definitions.) When the class’s suite finishes execution, ' - 'its\n' - 'execution frame is discarded but its local namespace is saved. [5] ' - 'A\n' - 'class object is then created using the inheritance list for the ' - 'base\n' - 'classes and the saved local namespace for the attribute ' - 'dictionary.\n' - 'The class name is bound to this class object in the original local\n' - 'namespace.\n' - '\n' - 'The order in which attributes are defined in the class body is\n' - 'preserved in the new class’s "__dict__". Note that this is ' - 'reliable\n' - 'only right after the class is created and only for classes that ' - 'were\n' - 'defined using the definition syntax.\n' - '\n' - 'Class creation can be customized heavily using metaclasses.\n' - '\n' - 'Classes can also be decorated: just like when decorating ' - 'functions,\n' - '\n' - ' @f1(arg)\n' - ' @f2\n' - ' class Foo: pass\n' - '\n' - 'is roughly equivalent to\n' - '\n' - ' class Foo: pass\n' - ' Foo = f1(arg)(f2(Foo))\n' - '\n' - 'The evaluation rules for the decorator expressions are the same as ' - 'for\n' - 'function decorators. The result is then bound to the class name.\n' - '\n' - 'Changed in version 3.9: Classes may be decorated with any valid\n' - '"assignment_expression". Previously, the grammar was much more\n' - 'restrictive; see **PEP 614** for details.\n' - '\n' - 'A list of type parameters may be given in square brackets ' - 'immediately\n' - 'after the class’s name. This indicates to static type checkers ' - 'that\n' - 'the class is generic. At runtime, the type parameters can be ' - 'retrieved\n' - 'from the class’s "__type_params__" attribute. See Generic classes ' - 'for\n' - 'more.\n' - '\n' - 'Changed in version 3.12: Type parameter lists are new in Python ' - '3.12.\n' - '\n' - '**Programmer’s note:** Variables defined in the class definition ' - 'are\n' - 'class attributes; they are shared by instances. Instance ' - 'attributes\n' - 'can be set in a method with "self.name = value". Both class and\n' - 'instance attributes are accessible through the notation ' - '“"self.name"”,\n' - 'and an instance attribute hides a class attribute with the same ' - 'name\n' - 'when accessed in this way. Class attributes can be used as ' - 'defaults\n' - 'for instance attributes, but using mutable values there can lead ' - 'to\n' - 'unexpected results. Descriptors can be used to create instance\n' - 'variables with different implementation details.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3115** - Metaclasses in Python 3000\n' - ' The proposal that changed the declaration of metaclasses to ' - 'the\n' - ' current syntax, and the semantics for how classes with\n' - ' metaclasses are constructed.\n' - '\n' - ' **PEP 3129** - Class Decorators\n' - ' The proposal that added class decorators. Function and ' - 'method\n' - ' decorators were introduced in **PEP 318**.\n', - 'comparisons': 'Comparisons\n' - '***********\n' - '\n' - 'Unlike C, all comparison operations in Python have the same ' - 'priority,\n' - 'which is lower than that of any arithmetic, shifting or ' - 'bitwise\n' - 'operation. Also unlike C, expressions like "a < b < c" have ' - 'the\n' - 'interpretation that is conventional in mathematics:\n' - '\n' - ' comparison ::= or_expr (comp_operator or_expr)*\n' - ' comp_operator ::= "<" | ">" | "==" | ">=" | "<=" | "!="\n' - ' | "is" ["not"] | ["not"] "in"\n' - '\n' - 'Comparisons yield boolean values: "True" or "False". Custom ' - '*rich\n' - 'comparison methods* may return non-boolean values. In this ' - 'case Python\n' - 'will call "bool()" on such value in boolean contexts.\n' - '\n' - 'Comparisons can be chained arbitrarily, e.g., "x < y <= z" ' - 'is\n' - 'equivalent to "x < y and y <= z", except that "y" is ' - 'evaluated only\n' - 'once (but in both cases "z" is not evaluated at all when "x < ' - 'y" is\n' - 'found to be false).\n' - '\n' - 'Formally, if *a*, *b*, *c*, …, *y*, *z* are expressions and ' - '*op1*,\n' - '*op2*, …, *opN* are comparison operators, then "a op1 b op2 c ' - '... y\n' - 'opN z" is equivalent to "a op1 b and b op2 c and ... y opN ' - 'z", except\n' - 'that each expression is evaluated at most once.\n' - '\n' - 'Note that "a op1 b op2 c" doesn’t imply any kind of ' - 'comparison between\n' - '*a* and *c*, so that, e.g., "x < y > z" is perfectly legal ' - '(though\n' - 'perhaps not pretty).\n' - '\n' - '\n' - 'Value comparisons\n' - '=================\n' - '\n' - 'The operators "<", ">", "==", ">=", "<=", and "!=" compare ' - 'the values\n' - 'of two objects. The objects do not need to have the same ' - 'type.\n' - '\n' - 'Chapter Objects, values and types states that objects have a ' - 'value (in\n' - 'addition to type and identity). The value of an object is a ' - 'rather\n' - 'abstract notion in Python: For example, there is no canonical ' - 'access\n' - 'method for an object’s value. Also, there is no requirement ' - 'that the\n' - 'value of an object should be constructed in a particular way, ' - 'e.g.\n' - 'comprised of all its data attributes. Comparison operators ' - 'implement a\n' - 'particular notion of what the value of an object is. One can ' - 'think of\n' - 'them as defining the value of an object indirectly, by means ' - 'of their\n' - 'comparison implementation.\n' - '\n' - 'Because all types are (direct or indirect) subtypes of ' - '"object", they\n' - 'inherit the default comparison behavior from "object". Types ' - 'can\n' - 'customize their comparison behavior by implementing *rich ' - 'comparison\n' - 'methods* like "__lt__()", described in Basic customization.\n' - '\n' - 'The default behavior for equality comparison ("==" and "!=") ' - 'is based\n' - 'on the identity of the objects. Hence, equality comparison ' - 'of\n' - 'instances with the same identity results in equality, and ' - 'equality\n' - 'comparison of instances with different identities results in\n' - 'inequality. A motivation for this default behavior is the ' - 'desire that\n' - 'all objects should be reflexive (i.e. "x is y" implies "x == ' - 'y").\n' - '\n' - 'A default order comparison ("<", ">", "<=", and ">=") is not ' - 'provided;\n' - 'an attempt raises "TypeError". A motivation for this default ' - 'behavior\n' - 'is the lack of a similar invariant as for equality.\n' - '\n' - 'The behavior of the default equality comparison, that ' - 'instances with\n' - 'different identities are always unequal, may be in contrast ' - 'to what\n' - 'types will need that have a sensible definition of object ' - 'value and\n' - 'value-based equality. Such types will need to customize ' - 'their\n' - 'comparison behavior, and in fact, a number of built-in types ' - 'have done\n' - 'that.\n' - '\n' - 'The following list describes the comparison behavior of the ' - 'most\n' - 'important built-in types.\n' - '\n' - '* Numbers of built-in numeric types (Numeric Types — int, ' - 'float,\n' - ' complex) and of the standard library types ' - '"fractions.Fraction" and\n' - ' "decimal.Decimal" can be compared within and across their ' - 'types,\n' - ' with the restriction that complex numbers do not support ' - 'order\n' - ' comparison. Within the limits of the types involved, they ' - 'compare\n' - ' mathematically (algorithmically) correct without loss of ' - 'precision.\n' - '\n' - ' The not-a-number values "float(\'NaN\')" and ' - '"decimal.Decimal(\'NaN\')"\n' - ' are special. Any ordered comparison of a number to a ' - 'not-a-number\n' - ' value is false. A counter-intuitive implication is that ' - 'not-a-number\n' - ' values are not equal to themselves. For example, if "x =\n' - ' float(\'NaN\')", "3 < x", "x < 3" and "x == x" are all ' - 'false, while "x\n' - ' != x" is true. This behavior is compliant with IEEE 754.\n' - '\n' - '* "None" and "NotImplemented" are singletons. **PEP 8** ' - 'advises that\n' - ' comparisons for singletons should always be done with "is" ' - 'or "is\n' - ' not", never the equality operators.\n' - '\n' - '* Binary sequences (instances of "bytes" or "bytearray") can ' - 'be\n' - ' compared within and across their types. They compare\n' - ' lexicographically using the numeric values of their ' - 'elements.\n' - '\n' - '* Strings (instances of "str") compare lexicographically ' - 'using the\n' - ' numerical Unicode code points (the result of the built-in ' - 'function\n' - ' "ord()") of their characters. [3]\n' - '\n' - ' Strings and binary sequences cannot be directly compared.\n' - '\n' - '* Sequences (instances of "tuple", "list", or "range") can be ' - 'compared\n' - ' only within each of their types, with the restriction that ' - 'ranges do\n' - ' not support order comparison. Equality comparison across ' - 'these\n' - ' types results in inequality, and ordering comparison across ' - 'these\n' - ' types raises "TypeError".\n' - '\n' - ' Sequences compare lexicographically using comparison of\n' - ' corresponding elements. The built-in containers typically ' - 'assume\n' - ' identical objects are equal to themselves. That lets them ' - 'bypass\n' - ' equality tests for identical objects to improve performance ' - 'and to\n' - ' maintain their internal invariants.\n' - '\n' - ' Lexicographical comparison between built-in collections ' - 'works as\n' - ' follows:\n' - '\n' - ' * For two collections to compare equal, they must be of the ' - 'same\n' - ' type, have the same length, and each pair of ' - 'corresponding\n' - ' elements must compare equal (for example, "[1,2] == ' - '(1,2)" is\n' - ' false because the type is not the same).\n' - '\n' - ' * Collections that support order comparison are ordered the ' - 'same as\n' - ' their first unequal elements (for example, "[1,2,x] <= ' - '[1,2,y]"\n' - ' has the same value as "x <= y"). If a corresponding ' - 'element does\n' - ' not exist, the shorter collection is ordered first (for ' - 'example,\n' - ' "[1,2] < [1,2,3]" is true).\n' - '\n' - '* Mappings (instances of "dict") compare equal if and only if ' - 'they\n' - ' have equal "(key, value)" pairs. Equality comparison of the ' - 'keys and\n' - ' values enforces reflexivity.\n' - '\n' - ' Order comparisons ("<", ">", "<=", and ">=") raise ' - '"TypeError".\n' - '\n' - '* Sets (instances of "set" or "frozenset") can be compared ' - 'within and\n' - ' across their types.\n' - '\n' - ' They define order comparison operators to mean subset and ' - 'superset\n' - ' tests. Those relations do not define total orderings (for ' - 'example,\n' - ' the two sets "{1,2}" and "{2,3}" are not equal, nor subsets ' - 'of one\n' - ' another, nor supersets of one another). Accordingly, sets ' - 'are not\n' - ' appropriate arguments for functions which depend on total ' - 'ordering\n' - ' (for example, "min()", "max()", and "sorted()" produce ' - 'undefined\n' - ' results given a list of sets as inputs).\n' - '\n' - ' Comparison of sets enforces reflexivity of its elements.\n' - '\n' - '* Most other built-in types have no comparison methods ' - 'implemented, so\n' - ' they inherit the default comparison behavior.\n' - '\n' - 'User-defined classes that customize their comparison behavior ' - 'should\n' - 'follow some consistency rules, if possible:\n' - '\n' - '* Equality comparison should be reflexive. In other words, ' - 'identical\n' - ' objects should compare equal:\n' - '\n' - ' "x is y" implies "x == y"\n' - '\n' - '* Comparison should be symmetric. In other words, the ' - 'following\n' - ' expressions should have the same result:\n' - '\n' - ' "x == y" and "y == x"\n' - '\n' - ' "x != y" and "y != x"\n' - '\n' - ' "x < y" and "y > x"\n' - '\n' - ' "x <= y" and "y >= x"\n' - '\n' - '* Comparison should be transitive. The following ' - '(non-exhaustive)\n' - ' examples illustrate that:\n' - '\n' - ' "x > y and y > z" implies "x > z"\n' - '\n' - ' "x < y and y <= z" implies "x < z"\n' - '\n' - '* Inverse comparison should result in the boolean negation. ' - 'In other\n' - ' words, the following expressions should have the same ' - 'result:\n' - '\n' - ' "x == y" and "not x != y"\n' - '\n' - ' "x < y" and "not x >= y" (for total ordering)\n' - '\n' - ' "x > y" and "not x <= y" (for total ordering)\n' - '\n' - ' The last two expressions apply to totally ordered ' - 'collections (e.g.\n' - ' to sequences, but not to sets or mappings). See also the\n' - ' "total_ordering()" decorator.\n' - '\n' - '* The "hash()" result should be consistent with equality. ' - 'Objects that\n' - ' are equal should either have the same hash value, or be ' - 'marked as\n' - ' unhashable.\n' - '\n' - 'Python does not enforce these consistency rules. In fact, ' - 'the\n' - 'not-a-number values are an example for not following these ' - 'rules.\n' - '\n' - '\n' - 'Membership test operations\n' - '==========================\n' - '\n' - 'The operators "in" and "not in" test for membership. "x in ' - 's"\n' - 'evaluates to "True" if *x* is a member of *s*, and "False" ' - 'otherwise.\n' - '"x not in s" returns the negation of "x in s". All built-in ' - 'sequences\n' - 'and set types support this as well as dictionary, for which ' - '"in" tests\n' - 'whether the dictionary has a given key. For container types ' - 'such as\n' - 'list, tuple, set, frozenset, dict, or collections.deque, the\n' - 'expression "x in y" is equivalent to "any(x is e or x == e ' - 'for e in\n' - 'y)".\n' - '\n' - 'For the string and bytes types, "x in y" is "True" if and ' - 'only if *x*\n' - 'is a substring of *y*. An equivalent test is "y.find(x) != ' - '-1".\n' - 'Empty strings are always considered to be a substring of any ' - 'other\n' - 'string, so """ in "abc"" will return "True".\n' - '\n' - 'For user-defined classes which define the "__contains__()" ' - 'method, "x\n' - 'in y" returns "True" if "y.__contains__(x)" returns a true ' - 'value, and\n' - '"False" otherwise.\n' - '\n' - 'For user-defined classes which do not define "__contains__()" ' - 'but do\n' - 'define "__iter__()", "x in y" is "True" if some value "z", ' - 'for which\n' - 'the expression "x is z or x == z" is true, is produced while ' - 'iterating\n' - 'over "y". If an exception is raised during the iteration, it ' - 'is as if\n' - '"in" raised that exception.\n' - '\n' - 'Lastly, the old-style iteration protocol is tried: if a class ' - 'defines\n' - '"__getitem__()", "x in y" is "True" if and only if there is a ' - 'non-\n' - 'negative integer index *i* such that "x is y[i] or x == ' - 'y[i]", and no\n' - 'lower integer index raises the "IndexError" exception. (If ' - 'any other\n' - 'exception is raised, it is as if "in" raised that ' - 'exception).\n' - '\n' - 'The operator "not in" is defined to have the inverse truth ' - 'value of\n' - '"in".\n' - '\n' - '\n' - 'Identity comparisons\n' - '====================\n' - '\n' - 'The operators "is" and "is not" test for an object’s ' - 'identity: "x is\n' - 'y" is true if and only if *x* and *y* are the same object. ' - 'An\n' - 'Object’s identity is determined using the "id()" function. ' - '"x is not\n' - 'y" yields the inverse truth value. [4]\n', - 'compound': 'Compound statements\n' - '*******************\n' - '\n' - 'Compound statements contain (groups of) other statements; they ' - 'affect\n' - 'or control the execution of those other statements in some way. ' - 'In\n' - 'general, compound statements span multiple lines, although in ' - 'simple\n' - 'incarnations a whole compound statement may be contained in one ' - 'line.\n' - '\n' - 'The "if", "while" and "for" statements implement traditional ' - 'control\n' - 'flow constructs. "try" specifies exception handlers and/or ' - 'cleanup\n' - 'code for a group of statements, while the "with" statement ' - 'allows the\n' - 'execution of initialization and finalization code around a block ' - 'of\n' - 'code. Function and class definitions are also syntactically ' - 'compound\n' - 'statements.\n' - '\n' - 'A compound statement consists of one or more ‘clauses.’ A ' - 'clause\n' - 'consists of a header and a ‘suite.’ The clause headers of a\n' - 'particular compound statement are all at the same indentation ' - 'level.\n' - 'Each clause header begins with a uniquely identifying keyword ' - 'and ends\n' - 'with a colon. A suite is a group of statements controlled by a\n' - 'clause. A suite can be one or more semicolon-separated simple\n' - 'statements on the same line as the header, following the ' - 'header’s\n' - 'colon, or it can be one or more indented statements on ' - 'subsequent\n' - 'lines. Only the latter form of a suite can contain nested ' - 'compound\n' - 'statements; the following is illegal, mostly because it wouldn’t ' - 'be\n' - 'clear to which "if" clause a following "else" clause would ' - 'belong:\n' - '\n' - ' if test1: if test2: print(x)\n' - '\n' - 'Also note that the semicolon binds tighter than the colon in ' - 'this\n' - 'context, so that in the following example, either all or none of ' - 'the\n' - '"print()" calls are executed:\n' - '\n' - ' if x < y < z: print(x); print(y); print(z)\n' - '\n' - 'Summarizing:\n' - '\n' - ' compound_stmt ::= if_stmt\n' - ' | while_stmt\n' - ' | for_stmt\n' - ' | try_stmt\n' - ' | with_stmt\n' - ' | match_stmt\n' - ' | funcdef\n' - ' | classdef\n' - ' | async_with_stmt\n' - ' | async_for_stmt\n' - ' | async_funcdef\n' - ' suite ::= stmt_list NEWLINE | NEWLINE INDENT ' - 'statement+ DEDENT\n' - ' statement ::= stmt_list NEWLINE | compound_stmt\n' - ' stmt_list ::= simple_stmt (";" simple_stmt)* [";"]\n' - '\n' - 'Note that statements always end in a "NEWLINE" possibly followed ' - 'by a\n' - '"DEDENT". Also note that optional continuation clauses always ' - 'begin\n' - 'with a keyword that cannot start a statement, thus there are no\n' - 'ambiguities (the ‘dangling "else"’ problem is solved in Python ' - 'by\n' - 'requiring nested "if" statements to be indented).\n' - '\n' - 'The formatting of the grammar rules in the following sections ' - 'places\n' - 'each clause on a separate line for clarity.\n' - '\n' - '\n' - 'The "if" statement\n' - '==================\n' - '\n' - 'The "if" statement is used for conditional execution:\n' - '\n' - ' if_stmt ::= "if" assignment_expression ":" suite\n' - ' ("elif" assignment_expression ":" suite)*\n' - ' ["else" ":" suite]\n' - '\n' - 'It selects exactly one of the suites by evaluating the ' - 'expressions one\n' - 'by one until one is found to be true (see section Boolean ' - 'operations\n' - 'for the definition of true and false); then that suite is ' - 'executed\n' - '(and no other part of the "if" statement is executed or ' - 'evaluated).\n' - 'If all expressions are false, the suite of the "else" clause, ' - 'if\n' - 'present, is executed.\n' - '\n' - '\n' - 'The "while" statement\n' - '=====================\n' - '\n' - 'The "while" statement is used for repeated execution as long as ' - 'an\n' - 'expression is true:\n' - '\n' - ' while_stmt ::= "while" assignment_expression ":" suite\n' - ' ["else" ":" suite]\n' - '\n' - 'This repeatedly tests the expression and, if it is true, ' - 'executes the\n' - 'first suite; if the expression is false (which may be the first ' - 'time\n' - 'it is tested) the suite of the "else" clause, if present, is ' - 'executed\n' - 'and the loop terminates.\n' - '\n' - 'A "break" statement executed in the first suite terminates the ' - 'loop\n' - 'without executing the "else" clause’s suite. A "continue" ' - 'statement\n' - 'executed in the first suite skips the rest of the suite and goes ' - 'back\n' - 'to testing the expression.\n' - '\n' - '\n' - 'The "for" statement\n' - '===================\n' - '\n' - 'The "for" statement is used to iterate over the elements of a ' - 'sequence\n' - '(such as a string, tuple or list) or other iterable object:\n' - '\n' - ' for_stmt ::= "for" target_list "in" starred_list ":" suite\n' - ' ["else" ":" suite]\n' - '\n' - 'The "starred_list" expression is evaluated once; it should yield ' - 'an\n' - '*iterable* object. An *iterator* is created for that iterable. ' - 'The\n' - 'first item provided by the iterator is then assigned to the ' - 'target\n' - 'list using the standard rules for assignments (see Assignment\n' - 'statements), and the suite is executed. This repeats for each ' - 'item\n' - 'provided by the iterator. When the iterator is exhausted, the ' - 'suite\n' - 'in the "else" clause, if present, is executed, and the loop\n' - 'terminates.\n' - '\n' - 'A "break" statement executed in the first suite terminates the ' - 'loop\n' - 'without executing the "else" clause’s suite. A "continue" ' - 'statement\n' - 'executed in the first suite skips the rest of the suite and ' - 'continues\n' - 'with the next item, or with the "else" clause if there is no ' - 'next\n' - 'item.\n' - '\n' - 'The for-loop makes assignments to the variables in the target ' - 'list.\n' - 'This overwrites all previous assignments to those variables ' - 'including\n' - 'those made in the suite of the for-loop:\n' - '\n' - ' for i in range(10):\n' - ' print(i)\n' - ' i = 5 # this will not affect the for-loop\n' - ' # because i will be overwritten with ' - 'the next\n' - ' # index in the range\n' - '\n' - 'Names in the target list are not deleted when the loop is ' - 'finished,\n' - 'but if the sequence is empty, they will not have been assigned ' - 'to at\n' - 'all by the loop. Hint: the built-in type "range()" represents\n' - 'immutable arithmetic sequences of integers. For instance, ' - 'iterating\n' - '"range(3)" successively yields 0, 1, and then 2.\n' - '\n' - 'Changed in version 3.11: Starred elements are now allowed in ' - 'the\n' - 'expression list.\n' - '\n' - '\n' - 'The "try" statement\n' - '===================\n' - '\n' - 'The "try" statement specifies exception handlers and/or cleanup ' - 'code\n' - 'for a group of statements:\n' - '\n' - ' try_stmt ::= try1_stmt | try2_stmt | try3_stmt\n' - ' try1_stmt ::= "try" ":" suite\n' - ' ("except" [expression ["as" identifier]] ":" ' - 'suite)+\n' - ' ["else" ":" suite]\n' - ' ["finally" ":" suite]\n' - ' try2_stmt ::= "try" ":" suite\n' - ' ("except" "*" expression ["as" identifier] ":" ' - 'suite)+\n' - ' ["else" ":" suite]\n' - ' ["finally" ":" suite]\n' - ' try3_stmt ::= "try" ":" suite\n' - ' "finally" ":" suite\n' - '\n' - 'Additional information on exceptions can be found in section\n' - 'Exceptions, and information on using the "raise" statement to ' - 'generate\n' - 'exceptions may be found in section The raise statement.\n' - '\n' - '\n' - '"except" clause\n' - '---------------\n' - '\n' - 'The "except" clause(s) specify one or more exception handlers. ' - 'When no\n' - 'exception occurs in the "try" clause, no exception handler is\n' - 'executed. When an exception occurs in the "try" suite, a search ' - 'for an\n' - 'exception handler is started. This search inspects the "except"\n' - 'clauses in turn until one is found that matches the exception. ' - 'An\n' - 'expression-less "except" clause, if present, must be last; it ' - 'matches\n' - 'any exception.\n' - '\n' - 'For an "except" clause with an expression, the expression must\n' - 'evaluate to an exception type or a tuple of exception types. ' - 'The\n' - 'raised exception matches an "except" clause whose expression ' - 'evaluates\n' - 'to the class or a *non-virtual base class* of the exception ' - 'object, or\n' - 'to a tuple that contains such a class.\n' - '\n' - 'If no "except" clause matches the exception, the search for an\n' - 'exception handler continues in the surrounding code and on the\n' - 'invocation stack. [1]\n' - '\n' - 'If the evaluation of an expression in the header of an "except" ' - 'clause\n' - 'raises an exception, the original search for a handler is ' - 'canceled and\n' - 'a search starts for the new exception in the surrounding code ' - 'and on\n' - 'the call stack (it is treated as if the entire "try" statement ' - 'raised\n' - 'the exception).\n' - '\n' - 'When a matching "except" clause is found, the exception is ' - 'assigned to\n' - 'the target specified after the "as" keyword in that "except" ' - 'clause,\n' - 'if present, and the "except" clause’s suite is executed. All ' - '"except"\n' - 'clauses must have an executable block. When the end of this ' - 'block is\n' - 'reached, execution continues normally after the entire "try"\n' - 'statement. (This means that if two nested handlers exist for the ' - 'same\n' - 'exception, and the exception occurs in the "try" clause of the ' - 'inner\n' - 'handler, the outer handler will not handle the exception.)\n' - '\n' - 'When an exception has been assigned using "as target", it is ' - 'cleared\n' - 'at the end of the "except" clause. This is as if\n' - '\n' - ' except E as N:\n' - ' foo\n' - '\n' - 'was translated to\n' - '\n' - ' except E as N:\n' - ' try:\n' - ' foo\n' - ' finally:\n' - ' del N\n' - '\n' - 'This means the exception must be assigned to a different name to ' - 'be\n' - 'able to refer to it after the "except" clause. Exceptions are ' - 'cleared\n' - 'because with the traceback attached to them, they form a ' - 'reference\n' - 'cycle with the stack frame, keeping all locals in that frame ' - 'alive\n' - 'until the next garbage collection occurs.\n' - '\n' - 'Before an "except" clause’s suite is executed, the exception is ' - 'stored\n' - 'in the "sys" module, where it can be accessed from within the ' - 'body of\n' - 'the "except" clause by calling "sys.exception()". When leaving ' - 'an\n' - 'exception handler, the exception stored in the "sys" module is ' - 'reset\n' - 'to its previous value:\n' - '\n' - ' >>> print(sys.exception())\n' - ' None\n' - ' >>> try:\n' - ' ... raise TypeError\n' - ' ... except:\n' - ' ... print(repr(sys.exception()))\n' - ' ... try:\n' - ' ... raise ValueError\n' - ' ... except:\n' - ' ... print(repr(sys.exception()))\n' - ' ... print(repr(sys.exception()))\n' - ' ...\n' - ' TypeError()\n' - ' ValueError()\n' - ' TypeError()\n' - ' >>> print(sys.exception())\n' - ' None\n' - '\n' - '\n' - '"except*" clause\n' - '----------------\n' - '\n' - 'The "except*" clause(s) are used for handling "ExceptionGroup"s. ' - 'The\n' - 'exception type for matching is interpreted as in the case of ' - '"except",\n' - 'but in the case of exception groups we can have partial matches ' - 'when\n' - 'the type matches some of the exceptions in the group. This means ' - 'that\n' - 'multiple "except*" clauses can execute, each handling part of ' - 'the\n' - 'exception group. Each clause executes at most once and handles ' - 'an\n' - 'exception group of all matching exceptions. Each exception in ' - 'the\n' - 'group is handled by at most one "except*" clause, the first ' - 'that\n' - 'matches it.\n' - '\n' - ' >>> try:\n' - ' ... raise ExceptionGroup("eg",\n' - ' ... [ValueError(1), TypeError(2), OSError(3), ' - 'OSError(4)])\n' - ' ... except* TypeError as e:\n' - " ... print(f'caught {type(e)} with nested " - "{e.exceptions}')\n" - ' ... except* OSError as e:\n' - " ... print(f'caught {type(e)} with nested " - "{e.exceptions}')\n" - ' ...\n' - " caught <class 'ExceptionGroup'> with nested (TypeError(2),)\n" - " caught <class 'ExceptionGroup'> with nested (OSError(3), " - 'OSError(4))\n' - ' + Exception Group Traceback (most recent call last):\n' - ' | File "<stdin>", line 2, in <module>\n' - ' | ExceptionGroup: eg\n' - ' +-+---------------- 1 ----------------\n' - ' | ValueError: 1\n' - ' +------------------------------------\n' - '\n' - 'Any remaining exceptions that were not handled by any "except*" ' - 'clause\n' - 'are re-raised at the end, along with all exceptions that were ' - 'raised\n' - 'from within the "except*" clauses. If this list contains more ' - 'than one\n' - 'exception to reraise, they are combined into an exception ' - 'group.\n' - '\n' - 'If the raised exception is not an exception group and its type ' - 'matches\n' - 'one of the "except*" clauses, it is caught and wrapped by an ' - 'exception\n' - 'group with an empty message string.\n' - '\n' - ' >>> try:\n' - ' ... raise BlockingIOError\n' - ' ... except* BlockingIOError as e:\n' - ' ... print(repr(e))\n' - ' ...\n' - " ExceptionGroup('', (BlockingIOError()))\n" - '\n' - 'An "except*" clause must have a matching expression; it cannot ' - 'be\n' - '"except*:". Furthermore, this expression cannot contain ' - 'exception\n' - 'group types, because that would have ambiguous semantics.\n' - '\n' - 'It is not possible to mix "except" and "except*" in the same ' - '"try".\n' - '"break", "continue" and "return" cannot appear in an "except*" ' - 'clause.\n' - '\n' - '\n' - '"else" clause\n' - '-------------\n' - '\n' - 'The optional "else" clause is executed if the control flow ' - 'leaves the\n' - '"try" suite, no exception was raised, and no "return", ' - '"continue", or\n' - '"break" statement was executed. Exceptions in the "else" clause ' - 'are\n' - 'not handled by the preceding "except" clauses.\n' - '\n' - '\n' - '"finally" clause\n' - '----------------\n' - '\n' - 'If "finally" is present, it specifies a ‘cleanup’ handler. The ' - '"try"\n' - 'clause is executed, including any "except" and "else" clauses. ' - 'If an\n' - 'exception occurs in any of the clauses and is not handled, the\n' - 'exception is temporarily saved. The "finally" clause is ' - 'executed. If\n' - 'there is a saved exception it is re-raised at the end of the ' - '"finally"\n' - 'clause. If the "finally" clause raises another exception, the ' - 'saved\n' - 'exception is set as the context of the new exception. If the ' - '"finally"\n' - 'clause executes a "return", "break" or "continue" statement, the ' - 'saved\n' - 'exception is discarded:\n' - '\n' - ' >>> def f():\n' - ' ... try:\n' - ' ... 1/0\n' - ' ... finally:\n' - ' ... return 42\n' - ' ...\n' - ' >>> f()\n' - ' 42\n' - '\n' - 'The exception information is not available to the program ' - 'during\n' - 'execution of the "finally" clause.\n' - '\n' - 'When a "return", "break" or "continue" statement is executed in ' - 'the\n' - '"try" suite of a "try"…"finally" statement, the "finally" clause ' - 'is\n' - 'also executed ‘on the way out.’\n' - '\n' - 'The return value of a function is determined by the last ' - '"return"\n' - 'statement executed. Since the "finally" clause always executes, ' - 'a\n' - '"return" statement executed in the "finally" clause will always ' - 'be the\n' - 'last one executed:\n' - '\n' - ' >>> def foo():\n' - ' ... try:\n' - " ... return 'try'\n" - ' ... finally:\n' - " ... return 'finally'\n" - ' ...\n' - ' >>> foo()\n' - " 'finally'\n" - '\n' - 'Changed in version 3.8: Prior to Python 3.8, a "continue" ' - 'statement\n' - 'was illegal in the "finally" clause due to a problem with the\n' - 'implementation.\n' - '\n' - '\n' - 'The "with" statement\n' - '====================\n' - '\n' - 'The "with" statement is used to wrap the execution of a block ' - 'with\n' - 'methods defined by a context manager (see section With ' - 'Statement\n' - 'Context Managers). This allows common "try"…"except"…"finally" ' - 'usage\n' - 'patterns to be encapsulated for convenient reuse.\n' - '\n' - ' with_stmt ::= "with" ( "(" with_stmt_contents ","? ' - '")" | with_stmt_contents ) ":" suite\n' - ' with_stmt_contents ::= with_item ("," with_item)*\n' - ' with_item ::= expression ["as" target]\n' - '\n' - 'The execution of the "with" statement with one “item” proceeds ' - 'as\n' - 'follows:\n' - '\n' - '1. The context expression (the expression given in the ' - '"with_item") is\n' - ' evaluated to obtain a context manager.\n' - '\n' - '2. The context manager’s "__enter__()" is loaded for later use.\n' - '\n' - '3. The context manager’s "__exit__()" is loaded for later use.\n' - '\n' - '4. The context manager’s "__enter__()" method is invoked.\n' - '\n' - '5. If a target was included in the "with" statement, the return ' - 'value\n' - ' from "__enter__()" is assigned to it.\n' - '\n' - ' Note:\n' - '\n' - ' The "with" statement guarantees that if the "__enter__()" ' - 'method\n' - ' returns without an error, then "__exit__()" will always be\n' - ' called. Thus, if an error occurs during the assignment to ' - 'the\n' - ' target list, it will be treated the same as an error ' - 'occurring\n' - ' within the suite would be. See step 7 below.\n' - '\n' - '6. The suite is executed.\n' - '\n' - '7. The context manager’s "__exit__()" method is invoked. If an\n' - ' exception caused the suite to be exited, its type, value, ' - 'and\n' - ' traceback are passed as arguments to "__exit__()". Otherwise, ' - 'three\n' - ' "None" arguments are supplied.\n' - '\n' - ' If the suite was exited due to an exception, and the return ' - 'value\n' - ' from the "__exit__()" method was false, the exception is ' - 'reraised.\n' - ' If the return value was true, the exception is suppressed, ' - 'and\n' - ' execution continues with the statement following the "with"\n' - ' statement.\n' - '\n' - ' If the suite was exited for any reason other than an ' - 'exception, the\n' - ' return value from "__exit__()" is ignored, and execution ' - 'proceeds\n' - ' at the normal location for the kind of exit that was taken.\n' - '\n' - 'The following code:\n' - '\n' - ' with EXPRESSION as TARGET:\n' - ' SUITE\n' - '\n' - 'is semantically equivalent to:\n' - '\n' - ' manager = (EXPRESSION)\n' - ' enter = type(manager).__enter__\n' - ' exit = type(manager).__exit__\n' - ' value = enter(manager)\n' - ' hit_except = False\n' - '\n' - ' try:\n' - ' TARGET = value\n' - ' SUITE\n' - ' except:\n' - ' hit_except = True\n' - ' if not exit(manager, *sys.exc_info()):\n' - ' raise\n' - ' finally:\n' - ' if not hit_except:\n' - ' exit(manager, None, None, None)\n' - '\n' - 'With more than one item, the context managers are processed as ' - 'if\n' - 'multiple "with" statements were nested:\n' - '\n' - ' with A() as a, B() as b:\n' - ' SUITE\n' - '\n' - 'is semantically equivalent to:\n' - '\n' - ' with A() as a:\n' - ' with B() as b:\n' - ' SUITE\n' - '\n' - 'You can also write multi-item context managers in multiple lines ' - 'if\n' - 'the items are surrounded by parentheses. For example:\n' - '\n' - ' with (\n' - ' A() as a,\n' - ' B() as b,\n' - ' ):\n' - ' SUITE\n' - '\n' - 'Changed in version 3.1: Support for multiple context ' - 'expressions.\n' - '\n' - 'Changed in version 3.10: Support for using grouping parentheses ' - 'to\n' - 'break the statement in multiple lines.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 343** - The “with” statement\n' - ' The specification, background, and examples for the Python ' - '"with"\n' - ' statement.\n' - '\n' - '\n' - 'The "match" statement\n' - '=====================\n' - '\n' - 'Added in version 3.10.\n' - '\n' - 'The match statement is used for pattern matching. Syntax:\n' - '\n' - ' match_stmt ::= \'match\' subject_expr ":" NEWLINE INDENT ' - 'case_block+ DEDENT\n' - ' subject_expr ::= star_named_expression "," ' - 'star_named_expressions?\n' - ' | named_expression\n' - ' case_block ::= \'case\' patterns [guard] ":" block\n' - '\n' - 'Note:\n' - '\n' - ' This section uses single quotes to denote soft keywords.\n' - '\n' - 'Pattern matching takes a pattern as input (following "case") and ' - 'a\n' - 'subject value (following "match"). The pattern (which may ' - 'contain\n' - 'subpatterns) is matched against the subject value. The outcomes ' - 'are:\n' - '\n' - '* A match success or failure (also termed a pattern success or\n' - ' failure).\n' - '\n' - '* Possible binding of matched values to a name. The ' - 'prerequisites for\n' - ' this are further discussed below.\n' - '\n' - 'The "match" and "case" keywords are soft keywords.\n' - '\n' - 'See also:\n' - '\n' - ' * **PEP 634** – Structural Pattern Matching: Specification\n' - '\n' - ' * **PEP 636** – Structural Pattern Matching: Tutorial\n' - '\n' - '\n' - 'Overview\n' - '--------\n' - '\n' - 'Here’s an overview of the logical flow of a match statement:\n' - '\n' - '1. The subject expression "subject_expr" is evaluated and a ' - 'resulting\n' - ' subject value obtained. If the subject expression contains a ' - 'comma,\n' - ' a tuple is constructed using the standard rules.\n' - '\n' - '2. Each pattern in a "case_block" is attempted to match with ' - 'the\n' - ' subject value. The specific rules for success or failure are\n' - ' described below. The match attempt can also bind some or all ' - 'of the\n' - ' standalone names within the pattern. The precise pattern ' - 'binding\n' - ' rules vary per pattern type and are specified below. **Name\n' - ' bindings made during a successful pattern match outlive the\n' - ' executed block and can be used after the match statement**.\n' - '\n' - ' Note:\n' - '\n' - ' During failed pattern matches, some subpatterns may ' - 'succeed. Do\n' - ' not rely on bindings being made for a failed match. ' - 'Conversely,\n' - ' do not rely on variables remaining unchanged after a ' - 'failed\n' - ' match. The exact behavior is dependent on implementation ' - 'and may\n' - ' vary. This is an intentional decision made to allow ' - 'different\n' - ' implementations to add optimizations.\n' - '\n' - '3. If the pattern succeeds, the corresponding guard (if present) ' - 'is\n' - ' evaluated. In this case all name bindings are guaranteed to ' - 'have\n' - ' happened.\n' - '\n' - ' * If the guard evaluates as true or is missing, the "block" ' - 'inside\n' - ' "case_block" is executed.\n' - '\n' - ' * Otherwise, the next "case_block" is attempted as described ' - 'above.\n' - '\n' - ' * If there are no further case blocks, the match statement ' - 'is\n' - ' completed.\n' - '\n' - 'Note:\n' - '\n' - ' Users should generally never rely on a pattern being ' - 'evaluated.\n' - ' Depending on implementation, the interpreter may cache values ' - 'or use\n' - ' other optimizations which skip repeated evaluations.\n' - '\n' - 'A sample match statement:\n' - '\n' - ' >>> flag = False\n' - ' >>> match (100, 200):\n' - ' ... case (100, 300): # Mismatch: 200 != 300\n' - " ... print('Case 1')\n" - ' ... case (100, 200) if flag: # Successful match, but ' - 'guard fails\n' - " ... print('Case 2')\n" - ' ... case (100, y): # Matches and binds y to 200\n' - " ... print(f'Case 3, y: {y}')\n" - ' ... case _: # Pattern not attempted\n' - " ... print('Case 4, I match anything!')\n" - ' ...\n' - ' Case 3, y: 200\n' - '\n' - 'In this case, "if flag" is a guard. Read more about that in the ' - 'next\n' - 'section.\n' - '\n' - '\n' - 'Guards\n' - '------\n' - '\n' - ' guard ::= "if" named_expression\n' - '\n' - 'A "guard" (which is part of the "case") must succeed for code ' - 'inside\n' - 'the "case" block to execute. It takes the form: "if" followed ' - 'by an\n' - 'expression.\n' - '\n' - 'The logical flow of a "case" block with a "guard" follows:\n' - '\n' - '1. Check that the pattern in the "case" block succeeded. If ' - 'the\n' - ' pattern failed, the "guard" is not evaluated and the next ' - '"case"\n' - ' block is checked.\n' - '\n' - '2. If the pattern succeeded, evaluate the "guard".\n' - '\n' - ' * If the "guard" condition evaluates as true, the case block ' - 'is\n' - ' selected.\n' - '\n' - ' * If the "guard" condition evaluates as false, the case block ' - 'is\n' - ' not selected.\n' - '\n' - ' * If the "guard" raises an exception during evaluation, the\n' - ' exception bubbles up.\n' - '\n' - 'Guards are allowed to have side effects as they are ' - 'expressions.\n' - 'Guard evaluation must proceed from the first to the last case ' - 'block,\n' - 'one at a time, skipping case blocks whose pattern(s) don’t all\n' - 'succeed. (I.e., guard evaluation must happen in order.) Guard\n' - 'evaluation must stop once a case block is selected.\n' - '\n' - '\n' - 'Irrefutable Case Blocks\n' - '-----------------------\n' - '\n' - 'An irrefutable case block is a match-all case block. A match\n' - 'statement may have at most one irrefutable case block, and it ' - 'must be\n' - 'last.\n' - '\n' - 'A case block is considered irrefutable if it has no guard and ' - 'its\n' - 'pattern is irrefutable. A pattern is considered irrefutable if ' - 'we can\n' - 'prove from its syntax alone that it will always succeed. Only ' - 'the\n' - 'following patterns are irrefutable:\n' - '\n' - '* AS Patterns whose left-hand side is irrefutable\n' - '\n' - '* OR Patterns containing at least one irrefutable pattern\n' - '\n' - '* Capture Patterns\n' - '\n' - '* Wildcard Patterns\n' - '\n' - '* parenthesized irrefutable patterns\n' - '\n' - '\n' - 'Patterns\n' - '--------\n' - '\n' - 'Note:\n' - '\n' - ' This section uses grammar notations beyond standard EBNF:\n' - '\n' - ' * the notation "SEP.RULE+" is shorthand for "RULE (SEP ' - 'RULE)*"\n' - '\n' - ' * the notation "!RULE" is shorthand for a negative lookahead\n' - ' assertion\n' - '\n' - 'The top-level syntax for "patterns" is:\n' - '\n' - ' patterns ::= open_sequence_pattern | pattern\n' - ' pattern ::= as_pattern | or_pattern\n' - ' closed_pattern ::= | literal_pattern\n' - ' | capture_pattern\n' - ' | wildcard_pattern\n' - ' | value_pattern\n' - ' | group_pattern\n' - ' | sequence_pattern\n' - ' | mapping_pattern\n' - ' | class_pattern\n' - '\n' - 'The descriptions below will include a description “in simple ' - 'terms” of\n' - 'what a pattern does for illustration purposes (credits to ' - 'Raymond\n' - 'Hettinger for a document that inspired most of the ' - 'descriptions). Note\n' - 'that these descriptions are purely for illustration purposes and ' - '**may\n' - 'not** reflect the underlying implementation. Furthermore, they ' - 'do not\n' - 'cover all valid forms.\n' - '\n' - '\n' - 'OR Patterns\n' - '~~~~~~~~~~~\n' - '\n' - 'An OR pattern is two or more patterns separated by vertical bars ' - '"|".\n' - 'Syntax:\n' - '\n' - ' or_pattern ::= "|".closed_pattern+\n' - '\n' - 'Only the final subpattern may be irrefutable, and each ' - 'subpattern must\n' - 'bind the same set of names to avoid ambiguity.\n' - '\n' - 'An OR pattern matches each of its subpatterns in turn to the ' - 'subject\n' - 'value, until one succeeds. The OR pattern is then considered\n' - 'successful. Otherwise, if none of the subpatterns succeed, the ' - 'OR\n' - 'pattern fails.\n' - '\n' - 'In simple terms, "P1 | P2 | ..." will try to match "P1", if it ' - 'fails\n' - 'it will try to match "P2", succeeding immediately if any ' - 'succeeds,\n' - 'failing otherwise.\n' - '\n' - '\n' - 'AS Patterns\n' - '~~~~~~~~~~~\n' - '\n' - 'An AS pattern matches an OR pattern on the left of the "as" ' - 'keyword\n' - 'against a subject. Syntax:\n' - '\n' - ' as_pattern ::= or_pattern "as" capture_pattern\n' - '\n' - 'If the OR pattern fails, the AS pattern fails. Otherwise, the ' - 'AS\n' - 'pattern binds the subject to the name on the right of the as ' - 'keyword\n' - 'and succeeds. "capture_pattern" cannot be a "_".\n' - '\n' - 'In simple terms "P as NAME" will match with "P", and on success ' - 'it\n' - 'will set "NAME = <subject>".\n' - '\n' - '\n' - 'Literal Patterns\n' - '~~~~~~~~~~~~~~~~\n' - '\n' - 'A literal pattern corresponds to most literals in Python. ' - 'Syntax:\n' - '\n' - ' literal_pattern ::= signed_number\n' - ' | signed_number "+" NUMBER\n' - ' | signed_number "-" NUMBER\n' - ' | strings\n' - ' | "None"\n' - ' | "True"\n' - ' | "False"\n' - ' signed_number ::= ["-"] NUMBER\n' - '\n' - 'The rule "strings" and the token "NUMBER" are defined in the ' - 'standard\n' - 'Python grammar. Triple-quoted strings are supported. Raw ' - 'strings and\n' - 'byte strings are supported. f-strings are not supported.\n' - '\n' - 'The forms "signed_number \'+\' NUMBER" and "signed_number \'-\' ' - 'NUMBER"\n' - 'are for expressing complex numbers; they require a real number ' - 'on the\n' - 'left and an imaginary number on the right. E.g. "3 + 4j".\n' - '\n' - 'In simple terms, "LITERAL" will succeed only if "<subject> ==\n' - 'LITERAL". For the singletons "None", "True" and "False", the ' - '"is"\n' - 'operator is used.\n' - '\n' - '\n' - 'Capture Patterns\n' - '~~~~~~~~~~~~~~~~\n' - '\n' - 'A capture pattern binds the subject value to a name. Syntax:\n' - '\n' - " capture_pattern ::= !'_' NAME\n" - '\n' - 'A single underscore "_" is not a capture pattern (this is what ' - '"!\'_\'"\n' - 'expresses). It is instead treated as a "wildcard_pattern".\n' - '\n' - 'In a given pattern, a given name can only be bound once. E.g. ' - '"case\n' - 'x, x: ..." is invalid while "case [x] | x: ..." is allowed.\n' - '\n' - 'Capture patterns always succeed. The binding follows scoping ' - 'rules\n' - 'established by the assignment expression operator in **PEP ' - '572**; the\n' - 'name becomes a local variable in the closest containing function ' - 'scope\n' - 'unless there’s an applicable "global" or "nonlocal" statement.\n' - '\n' - 'In simple terms "NAME" will always succeed and it will set "NAME ' - '=\n' - '<subject>".\n' - '\n' - '\n' - 'Wildcard Patterns\n' - '~~~~~~~~~~~~~~~~~\n' - '\n' - 'A wildcard pattern always succeeds (matches anything) and binds ' - 'no\n' - 'name. Syntax:\n' - '\n' - " wildcard_pattern ::= '_'\n" - '\n' - '"_" is a soft keyword within any pattern, but only within ' - 'patterns.\n' - 'It is an identifier, as usual, even within "match" subject\n' - 'expressions, "guard"s, and "case" blocks.\n' - '\n' - 'In simple terms, "_" will always succeed.\n' - '\n' - '\n' - 'Value Patterns\n' - '~~~~~~~~~~~~~~\n' - '\n' - 'A value pattern represents a named value in Python. Syntax:\n' - '\n' - ' value_pattern ::= attr\n' - ' attr ::= name_or_attr "." NAME\n' - ' name_or_attr ::= attr | NAME\n' - '\n' - 'The dotted name in the pattern is looked up using standard ' - 'Python name\n' - 'resolution rules. The pattern succeeds if the value found ' - 'compares\n' - 'equal to the subject value (using the "==" equality operator).\n' - '\n' - 'In simple terms "NAME1.NAME2" will succeed only if "<subject> ' - '==\n' - 'NAME1.NAME2"\n' - '\n' - 'Note:\n' - '\n' - ' If the same value occurs multiple times in the same match ' - 'statement,\n' - ' the interpreter may cache the first value found and reuse it ' - 'rather\n' - ' than repeat the same lookup. This cache is strictly tied to a ' - 'given\n' - ' execution of a given match statement.\n' - '\n' - '\n' - 'Group Patterns\n' - '~~~~~~~~~~~~~~\n' - '\n' - 'A group pattern allows users to add parentheses around patterns ' - 'to\n' - 'emphasize the intended grouping. Otherwise, it has no ' - 'additional\n' - 'syntax. Syntax:\n' - '\n' - ' group_pattern ::= "(" pattern ")"\n' - '\n' - 'In simple terms "(P)" has the same effect as "P".\n' - '\n' - '\n' - 'Sequence Patterns\n' - '~~~~~~~~~~~~~~~~~\n' - '\n' - 'A sequence pattern contains several subpatterns to be matched ' - 'against\n' - 'sequence elements. The syntax is similar to the unpacking of a ' - 'list or\n' - 'tuple.\n' - '\n' - ' sequence_pattern ::= "[" [maybe_sequence_pattern] "]"\n' - ' | "(" [open_sequence_pattern] ")"\n' - ' open_sequence_pattern ::= maybe_star_pattern "," ' - '[maybe_sequence_pattern]\n' - ' maybe_sequence_pattern ::= ",".maybe_star_pattern+ ","?\n' - ' maybe_star_pattern ::= star_pattern | pattern\n' - ' star_pattern ::= "*" (capture_pattern | ' - 'wildcard_pattern)\n' - '\n' - 'There is no difference if parentheses or square brackets are ' - 'used for\n' - 'sequence patterns (i.e. "(...)" vs "[...]" ).\n' - '\n' - 'Note:\n' - '\n' - ' A single pattern enclosed in parentheses without a trailing ' - 'comma\n' - ' (e.g. "(3 | 4)") is a group pattern. While a single pattern ' - 'enclosed\n' - ' in square brackets (e.g. "[3 | 4]") is still a sequence ' - 'pattern.\n' - '\n' - 'At most one star subpattern may be in a sequence pattern. The ' - 'star\n' - 'subpattern may occur in any position. If no star subpattern is\n' - 'present, the sequence pattern is a fixed-length sequence ' - 'pattern;\n' - 'otherwise it is a variable-length sequence pattern.\n' - '\n' - 'The following is the logical flow for matching a sequence ' - 'pattern\n' - 'against a subject value:\n' - '\n' - '1. If the subject value is not a sequence [2], the sequence ' - 'pattern\n' - ' fails.\n' - '\n' - '2. If the subject value is an instance of "str", "bytes" or\n' - ' "bytearray" the sequence pattern fails.\n' - '\n' - '3. The subsequent steps depend on whether the sequence pattern ' - 'is\n' - ' fixed or variable-length.\n' - '\n' - ' If the sequence pattern is fixed-length:\n' - '\n' - ' 1. If the length of the subject sequence is not equal to the ' - 'number\n' - ' of subpatterns, the sequence pattern fails\n' - '\n' - ' 2. Subpatterns in the sequence pattern are matched to their\n' - ' corresponding items in the subject sequence from left to ' - 'right.\n' - ' Matching stops as soon as a subpattern fails. If all\n' - ' subpatterns succeed in matching their corresponding item, ' - 'the\n' - ' sequence pattern succeeds.\n' - '\n' - ' Otherwise, if the sequence pattern is variable-length:\n' - '\n' - ' 1. If the length of the subject sequence is less than the ' - 'number of\n' - ' non-star subpatterns, the sequence pattern fails.\n' - '\n' - ' 2. The leading non-star subpatterns are matched to their\n' - ' corresponding items as for fixed-length sequences.\n' - '\n' - ' 3. If the previous step succeeds, the star subpattern matches ' - 'a\n' - ' list formed of the remaining subject items, excluding the\n' - ' remaining items corresponding to non-star subpatterns ' - 'following\n' - ' the star subpattern.\n' - '\n' - ' 4. Remaining non-star subpatterns are matched to their\n' - ' corresponding subject items, as for a fixed-length ' - 'sequence.\n' - '\n' - ' Note:\n' - '\n' - ' The length of the subject sequence is obtained via "len()" ' - '(i.e.\n' - ' via the "__len__()" protocol). This length may be cached ' - 'by the\n' - ' interpreter in a similar manner as value patterns.\n' - '\n' - 'In simple terms "[P1, P2, P3," … ", P<N>]" matches only if all ' - 'the\n' - 'following happens:\n' - '\n' - '* check "<subject>" is a sequence\n' - '\n' - '* "len(subject) == <N>"\n' - '\n' - '* "P1" matches "<subject>[0]" (note that this match can also ' - 'bind\n' - ' names)\n' - '\n' - '* "P2" matches "<subject>[1]" (note that this match can also ' - 'bind\n' - ' names)\n' - '\n' - '* … and so on for the corresponding pattern/element.\n' - '\n' - '\n' - 'Mapping Patterns\n' - '~~~~~~~~~~~~~~~~\n' - '\n' - 'A mapping pattern contains one or more key-value patterns. The ' - 'syntax\n' - 'is similar to the construction of a dictionary. Syntax:\n' - '\n' - ' mapping_pattern ::= "{" [items_pattern] "}"\n' - ' items_pattern ::= ",".key_value_pattern+ ","?\n' - ' key_value_pattern ::= (literal_pattern | value_pattern) ":" ' - 'pattern\n' - ' | double_star_pattern\n' - ' double_star_pattern ::= "**" capture_pattern\n' - '\n' - 'At most one double star pattern may be in a mapping pattern. ' - 'The\n' - 'double star pattern must be the last subpattern in the mapping\n' - 'pattern.\n' - '\n' - 'Duplicate keys in mapping patterns are disallowed. Duplicate ' - 'literal\n' - 'keys will raise a "SyntaxError". Two keys that otherwise have ' - 'the same\n' - 'value will raise a "ValueError" at runtime.\n' - '\n' - 'The following is the logical flow for matching a mapping ' - 'pattern\n' - 'against a subject value:\n' - '\n' - '1. If the subject value is not a mapping [3],the mapping ' - 'pattern\n' - ' fails.\n' - '\n' - '2. If every key given in the mapping pattern is present in the ' - 'subject\n' - ' mapping, and the pattern for each key matches the ' - 'corresponding\n' - ' item of the subject mapping, the mapping pattern succeeds.\n' - '\n' - '3. If duplicate keys are detected in the mapping pattern, the ' - 'pattern\n' - ' is considered invalid. A "SyntaxError" is raised for ' - 'duplicate\n' - ' literal values; or a "ValueError" for named keys of the same ' - 'value.\n' - '\n' - 'Note:\n' - '\n' - ' Key-value pairs are matched using the two-argument form of ' - 'the\n' - ' mapping subject’s "get()" method. Matched key-value pairs ' - 'must\n' - ' already be present in the mapping, and not created on-the-fly ' - 'via\n' - ' "__missing__()" or "__getitem__()".\n' - '\n' - 'In simple terms "{KEY1: P1, KEY2: P2, ... }" matches only if all ' - 'the\n' - 'following happens:\n' - '\n' - '* check "<subject>" is a mapping\n' - '\n' - '* "KEY1 in <subject>"\n' - '\n' - '* "P1" matches "<subject>[KEY1]"\n' - '\n' - '* … and so on for the corresponding KEY/pattern pair.\n' - '\n' - '\n' - 'Class Patterns\n' - '~~~~~~~~~~~~~~\n' - '\n' - 'A class pattern represents a class and its positional and ' - 'keyword\n' - 'arguments (if any). Syntax:\n' - '\n' - ' class_pattern ::= name_or_attr "(" [pattern_arguments ' - '","?] ")"\n' - ' pattern_arguments ::= positional_patterns ["," ' - 'keyword_patterns]\n' - ' | keyword_patterns\n' - ' positional_patterns ::= ",".pattern+\n' - ' keyword_patterns ::= ",".keyword_pattern+\n' - ' keyword_pattern ::= NAME "=" pattern\n' - '\n' - 'The same keyword should not be repeated in class patterns.\n' - '\n' - 'The following is the logical flow for matching a class pattern ' - 'against\n' - 'a subject value:\n' - '\n' - '1. If "name_or_attr" is not an instance of the builtin "type" , ' - 'raise\n' - ' "TypeError".\n' - '\n' - '2. If the subject value is not an instance of "name_or_attr" ' - '(tested\n' - ' via "isinstance()"), the class pattern fails.\n' - '\n' - '3. If no pattern arguments are present, the pattern succeeds.\n' - ' Otherwise, the subsequent steps depend on whether keyword or\n' - ' positional argument patterns are present.\n' - '\n' - ' For a number of built-in types (specified below), a single\n' - ' positional subpattern is accepted which will match the ' - 'entire\n' - ' subject; for these types keyword patterns also work as for ' - 'other\n' - ' types.\n' - '\n' - ' If only keyword patterns are present, they are processed as\n' - ' follows, one by one:\n' - '\n' - ' I. The keyword is looked up as an attribute on the subject.\n' - '\n' - ' * If this raises an exception other than "AttributeError", ' - 'the\n' - ' exception bubbles up.\n' - '\n' - ' * If this raises "AttributeError", the class pattern has ' - 'failed.\n' - '\n' - ' * Else, the subpattern associated with the keyword pattern ' - 'is\n' - ' matched against the subject’s attribute value. If this ' - 'fails,\n' - ' the class pattern fails; if this succeeds, the match ' - 'proceeds\n' - ' to the next keyword.\n' - '\n' - ' II. If all keyword patterns succeed, the class pattern ' - 'succeeds.\n' - '\n' - ' If any positional patterns are present, they are converted ' - 'to\n' - ' keyword patterns using the "__match_args__" attribute on the ' - 'class\n' - ' "name_or_attr" before matching:\n' - '\n' - ' I. The equivalent of "getattr(cls, "__match_args__", ())" is\n' - ' called.\n' - '\n' - ' * If this raises an exception, the exception bubbles up.\n' - '\n' - ' * If the returned value is not a tuple, the conversion ' - 'fails and\n' - ' "TypeError" is raised.\n' - '\n' - ' * If there are more positional patterns than\n' - ' "len(cls.__match_args__)", "TypeError" is raised.\n' - '\n' - ' * Otherwise, positional pattern "i" is converted to a ' - 'keyword\n' - ' pattern using "__match_args__[i]" as the keyword.\n' - ' "__match_args__[i]" must be a string; if not "TypeError" ' - 'is\n' - ' raised.\n' - '\n' - ' * If there are duplicate keywords, "TypeError" is raised.\n' - '\n' - ' See also:\n' - '\n' - ' Customizing positional arguments in class pattern ' - 'matching\n' - '\n' - ' II. Once all positional patterns have been converted to ' - 'keyword\n' - ' patterns,\n' - ' the match proceeds as if there were only keyword ' - 'patterns.\n' - '\n' - ' For the following built-in types the handling of positional\n' - ' subpatterns is different:\n' - '\n' - ' * "bool"\n' - '\n' - ' * "bytearray"\n' - '\n' - ' * "bytes"\n' - '\n' - ' * "dict"\n' - '\n' - ' * "float"\n' - '\n' - ' * "frozenset"\n' - '\n' - ' * "int"\n' - '\n' - ' * "list"\n' - '\n' - ' * "set"\n' - '\n' - ' * "str"\n' - '\n' - ' * "tuple"\n' - '\n' - ' These classes accept a single positional argument, and the ' - 'pattern\n' - ' there is matched against the whole object rather than an ' - 'attribute.\n' - ' For example "int(0|1)" matches the value "0", but not the ' - 'value\n' - ' "0.0".\n' - '\n' - 'In simple terms "CLS(P1, attr=P2)" matches only if the ' - 'following\n' - 'happens:\n' - '\n' - '* "isinstance(<subject>, CLS)"\n' - '\n' - '* convert "P1" to a keyword pattern using "CLS.__match_args__"\n' - '\n' - '* For each keyword argument "attr=P2":\n' - '\n' - ' * "hasattr(<subject>, "attr")"\n' - '\n' - ' * "P2" matches "<subject>.attr"\n' - '\n' - '* … and so on for the corresponding keyword argument/pattern ' - 'pair.\n' - '\n' - 'See also:\n' - '\n' - ' * **PEP 634** – Structural Pattern Matching: Specification\n' - '\n' - ' * **PEP 636** – Structural Pattern Matching: Tutorial\n' - '\n' - '\n' - 'Function definitions\n' - '====================\n' - '\n' - 'A function definition defines a user-defined function object ' - '(see\n' - 'section The standard type hierarchy):\n' - '\n' - ' funcdef ::= [decorators] "def" funcname ' - '[type_params] "(" [parameter_list] ")"\n' - ' ["->" expression] ":" suite\n' - ' decorators ::= decorator+\n' - ' decorator ::= "@" assignment_expression ' - 'NEWLINE\n' - ' parameter_list ::= defparameter ("," ' - 'defparameter)* "," "/" ["," [parameter_list_no_posonly]]\n' - ' | parameter_list_no_posonly\n' - ' parameter_list_no_posonly ::= defparameter ("," ' - 'defparameter)* ["," [parameter_list_starargs]]\n' - ' | parameter_list_starargs\n' - ' parameter_list_starargs ::= "*" [star_parameter] ("," ' - 'defparameter)* ["," ["**" parameter [","]]]\n' - ' | "**" parameter [","]\n' - ' parameter ::= identifier [":" expression]\n' - ' star_parameter ::= identifier [":" ["*"] ' - 'expression]\n' - ' defparameter ::= parameter ["=" expression]\n' - ' funcname ::= identifier\n' - '\n' - 'A function definition is an executable statement. Its execution ' - 'binds\n' - 'the function name in the current local namespace to a function ' - 'object\n' - '(a wrapper around the executable code for the function). This\n' - 'function object contains a reference to the current global ' - 'namespace\n' - 'as the global namespace to be used when the function is called.\n' - '\n' - 'The function definition does not execute the function body; this ' - 'gets\n' - 'executed only when the function is called. [4]\n' - '\n' - 'A function definition may be wrapped by one or more *decorator*\n' - 'expressions. Decorator expressions are evaluated when the ' - 'function is\n' - 'defined, in the scope that contains the function definition. ' - 'The\n' - 'result must be a callable, which is invoked with the function ' - 'object\n' - 'as the only argument. The returned value is bound to the ' - 'function name\n' - 'instead of the function object. Multiple decorators are applied ' - 'in\n' - 'nested fashion. For example, the following code\n' - '\n' - ' @f1(arg)\n' - ' @f2\n' - ' def func(): pass\n' - '\n' - 'is roughly equivalent to\n' - '\n' - ' def func(): pass\n' - ' func = f1(arg)(f2(func))\n' - '\n' - 'except that the original function is not temporarily bound to ' - 'the name\n' - '"func".\n' - '\n' - 'Changed in version 3.9: Functions may be decorated with any ' - 'valid\n' - '"assignment_expression". Previously, the grammar was much more\n' - 'restrictive; see **PEP 614** for details.\n' - '\n' - 'A list of type parameters may be given in square brackets ' - 'between the\n' - 'function’s name and the opening parenthesis for its parameter ' - 'list.\n' - 'This indicates to static type checkers that the function is ' - 'generic.\n' - 'At runtime, the type parameters can be retrieved from the ' - 'function’s\n' - '"__type_params__" attribute. See Generic functions for more.\n' - '\n' - 'Changed in version 3.12: Type parameter lists are new in Python ' - '3.12.\n' - '\n' - 'When one or more *parameters* have the form *parameter* "="\n' - '*expression*, the function is said to have “default parameter ' - 'values.”\n' - 'For a parameter with a default value, the corresponding ' - '*argument* may\n' - 'be omitted from a call, in which case the parameter’s default ' - 'value is\n' - 'substituted. If a parameter has a default value, all following\n' - 'parameters up until the “"*"” must also have a default value — ' - 'this is\n' - 'a syntactic restriction that is not expressed by the grammar.\n' - '\n' - '**Default parameter values are evaluated from left to right when ' - 'the\n' - 'function definition is executed.** This means that the ' - 'expression is\n' - 'evaluated once, when the function is defined, and that the same ' - '“pre-\n' - 'computed” value is used for each call. This is especially ' - 'important\n' - 'to understand when a default parameter value is a mutable ' - 'object, such\n' - 'as a list or a dictionary: if the function modifies the object ' - '(e.g.\n' - 'by appending an item to a list), the default parameter value is ' - 'in\n' - 'effect modified. This is generally not what was intended. A ' - 'way\n' - 'around this is to use "None" as the default, and explicitly test ' - 'for\n' - 'it in the body of the function, e.g.:\n' - '\n' - ' def whats_on_the_telly(penguin=None):\n' - ' if penguin is None:\n' - ' penguin = []\n' - ' penguin.append("property of the zoo")\n' - ' return penguin\n' - '\n' - 'Function call semantics are described in more detail in section ' - 'Calls.\n' - 'A function call always assigns values to all parameters ' - 'mentioned in\n' - 'the parameter list, either from positional arguments, from ' - 'keyword\n' - 'arguments, or from default values. If the form “"*identifier"” ' - 'is\n' - 'present, it is initialized to a tuple receiving any excess ' - 'positional\n' - 'parameters, defaulting to the empty tuple. If the form\n' - '“"**identifier"” is present, it is initialized to a new ordered\n' - 'mapping receiving any excess keyword arguments, defaulting to a ' - 'new\n' - 'empty mapping of the same type. Parameters after “"*"” or\n' - '“"*identifier"” are keyword-only parameters and may only be ' - 'passed by\n' - 'keyword arguments. Parameters before “"/"” are positional-only\n' - 'parameters and may only be passed by positional arguments.\n' - '\n' - 'Changed in version 3.8: The "/" function parameter syntax may be ' - 'used\n' - 'to indicate positional-only parameters. See **PEP 570** for ' - 'details.\n' - '\n' - 'Parameters may have an *annotation* of the form “": ' - 'expression"”\n' - 'following the parameter name. Any parameter may have an ' - 'annotation,\n' - 'even those of the form "*identifier" or "**identifier". (As a ' - 'special\n' - 'case, parameters of the form "*identifier" may have an ' - 'annotation “":\n' - '*expression"”.) Functions may have “return” annotation of the ' - 'form\n' - '“"-> expression"” after the parameter list. These annotations ' - 'can be\n' - 'any valid Python expression. The presence of annotations does ' - 'not\n' - 'change the semantics of a function. See Annotations for more\n' - 'information on annotations.\n' - '\n' - 'Changed in version 3.11: Parameters of the form “"*identifier"” ' - 'may\n' - 'have an annotation “": *expression"”. See **PEP 646**.\n' - '\n' - 'It is also possible to create anonymous functions (functions not ' - 'bound\n' - 'to a name), for immediate use in expressions. This uses lambda\n' - 'expressions, described in section Lambdas. Note that the ' - 'lambda\n' - 'expression is merely a shorthand for a simplified function ' - 'definition;\n' - 'a function defined in a “"def"” statement can be passed around ' - 'or\n' - 'assigned to another name just like a function defined by a ' - 'lambda\n' - 'expression. The “"def"” form is actually more powerful since ' - 'it\n' - 'allows the execution of multiple statements and annotations.\n' - '\n' - '**Programmer’s note:** Functions are first-class objects. A ' - '“"def"”\n' - 'statement executed inside a function definition defines a local\n' - 'function that can be returned or passed around. Free variables ' - 'used\n' - 'in the nested function can access the local variables of the ' - 'function\n' - 'containing the def. See section Naming and binding for ' - 'details.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3107** - Function Annotations\n' - ' The original specification for function annotations.\n' - '\n' - ' **PEP 484** - Type Hints\n' - ' Definition of a standard meaning for annotations: type ' - 'hints.\n' - '\n' - ' **PEP 526** - Syntax for Variable Annotations\n' - ' Ability to type hint variable declarations, including ' - 'class\n' - ' variables and instance variables.\n' - '\n' - ' **PEP 563** - Postponed Evaluation of Annotations\n' - ' Support for forward references within annotations by ' - 'preserving\n' - ' annotations in a string form at runtime instead of eager\n' - ' evaluation.\n' - '\n' - ' **PEP 318** - Decorators for Functions and Methods\n' - ' Function and method decorators were introduced. Class ' - 'decorators\n' - ' were introduced in **PEP 3129**.\n' - '\n' - '\n' - 'Class definitions\n' - '=================\n' - '\n' - 'A class definition defines a class object (see section The ' - 'standard\n' - 'type hierarchy):\n' - '\n' - ' classdef ::= [decorators] "class" classname [type_params] ' - '[inheritance] ":" suite\n' - ' inheritance ::= "(" [argument_list] ")"\n' - ' classname ::= identifier\n' - '\n' - 'A class definition is an executable statement. The inheritance ' - 'list\n' - 'usually gives a list of base classes (see Metaclasses for more\n' - 'advanced uses), so each item in the list should evaluate to a ' - 'class\n' - 'object which allows subclassing. Classes without an inheritance ' - 'list\n' - 'inherit, by default, from the base class "object"; hence,\n' - '\n' - ' class Foo:\n' - ' pass\n' - '\n' - 'is equivalent to\n' - '\n' - ' class Foo(object):\n' - ' pass\n' - '\n' - 'The class’s suite is then executed in a new execution frame ' - '(see\n' - 'Naming and binding), using a newly created local namespace and ' - 'the\n' - 'original global namespace. (Usually, the suite contains mostly\n' - 'function definitions.) When the class’s suite finishes ' - 'execution, its\n' - 'execution frame is discarded but its local namespace is saved. ' - '[5] A\n' - 'class object is then created using the inheritance list for the ' - 'base\n' - 'classes and the saved local namespace for the attribute ' - 'dictionary.\n' - 'The class name is bound to this class object in the original ' - 'local\n' - 'namespace.\n' - '\n' - 'The order in which attributes are defined in the class body is\n' - 'preserved in the new class’s "__dict__". Note that this is ' - 'reliable\n' - 'only right after the class is created and only for classes that ' - 'were\n' - 'defined using the definition syntax.\n' - '\n' - 'Class creation can be customized heavily using metaclasses.\n' - '\n' - 'Classes can also be decorated: just like when decorating ' - 'functions,\n' - '\n' - ' @f1(arg)\n' - ' @f2\n' - ' class Foo: pass\n' - '\n' - 'is roughly equivalent to\n' - '\n' - ' class Foo: pass\n' - ' Foo = f1(arg)(f2(Foo))\n' - '\n' - 'The evaluation rules for the decorator expressions are the same ' - 'as for\n' - 'function decorators. The result is then bound to the class ' - 'name.\n' - '\n' - 'Changed in version 3.9: Classes may be decorated with any valid\n' - '"assignment_expression". Previously, the grammar was much more\n' - 'restrictive; see **PEP 614** for details.\n' - '\n' - 'A list of type parameters may be given in square brackets ' - 'immediately\n' - 'after the class’s name. This indicates to static type checkers ' - 'that\n' - 'the class is generic. At runtime, the type parameters can be ' - 'retrieved\n' - 'from the class’s "__type_params__" attribute. See Generic ' - 'classes for\n' - 'more.\n' - '\n' - 'Changed in version 3.12: Type parameter lists are new in Python ' - '3.12.\n' - '\n' - '**Programmer’s note:** Variables defined in the class definition ' - 'are\n' - 'class attributes; they are shared by instances. Instance ' - 'attributes\n' - 'can be set in a method with "self.name = value". Both class ' - 'and\n' - 'instance attributes are accessible through the notation ' - '“"self.name"”,\n' - 'and an instance attribute hides a class attribute with the same ' - 'name\n' - 'when accessed in this way. Class attributes can be used as ' - 'defaults\n' - 'for instance attributes, but using mutable values there can lead ' - 'to\n' - 'unexpected results. Descriptors can be used to create instance\n' - 'variables with different implementation details.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3115** - Metaclasses in Python 3000\n' - ' The proposal that changed the declaration of metaclasses to ' - 'the\n' - ' current syntax, and the semantics for how classes with\n' - ' metaclasses are constructed.\n' - '\n' - ' **PEP 3129** - Class Decorators\n' - ' The proposal that added class decorators. Function and ' - 'method\n' - ' decorators were introduced in **PEP 318**.\n' - '\n' - '\n' - 'Coroutines\n' - '==========\n' - '\n' - 'Added in version 3.5.\n' - '\n' - '\n' - 'Coroutine function definition\n' - '-----------------------------\n' - '\n' - ' async_funcdef ::= [decorators] "async" "def" funcname "(" ' - '[parameter_list] ")"\n' - ' ["->" expression] ":" suite\n' - '\n' - 'Execution of Python coroutines can be suspended and resumed at ' - 'many\n' - 'points (see *coroutine*). "await" expressions, "async for" and ' - '"async\n' - 'with" can only be used in the body of a coroutine function.\n' - '\n' - 'Functions defined with "async def" syntax are always coroutine\n' - 'functions, even if they do not contain "await" or "async" ' - 'keywords.\n' - '\n' - 'It is a "SyntaxError" to use a "yield from" expression inside ' - 'the body\n' - 'of a coroutine function.\n' - '\n' - 'An example of a coroutine function:\n' - '\n' - ' async def func(param1, param2):\n' - ' do_stuff()\n' - ' await some_coroutine()\n' - '\n' - 'Changed in version 3.7: "await" and "async" are now keywords;\n' - 'previously they were only treated as such inside the body of a\n' - 'coroutine function.\n' - '\n' - '\n' - 'The "async for" statement\n' - '-------------------------\n' - '\n' - ' async_for_stmt ::= "async" for_stmt\n' - '\n' - 'An *asynchronous iterable* provides an "__aiter__" method that\n' - 'directly returns an *asynchronous iterator*, which can call\n' - 'asynchronous code in its "__anext__" method.\n' - '\n' - 'The "async for" statement allows convenient iteration over\n' - 'asynchronous iterables.\n' - '\n' - 'The following code:\n' - '\n' - ' async for TARGET in ITER:\n' - ' SUITE\n' - ' else:\n' - ' SUITE2\n' - '\n' - 'Is semantically equivalent to:\n' - '\n' - ' iter = (ITER)\n' - ' iter = type(iter).__aiter__(iter)\n' - ' running = True\n' - '\n' - ' while running:\n' - ' try:\n' - ' TARGET = await type(iter).__anext__(iter)\n' - ' except StopAsyncIteration:\n' - ' running = False\n' - ' else:\n' - ' SUITE\n' - ' else:\n' - ' SUITE2\n' - '\n' - 'See also "__aiter__()" and "__anext__()" for details.\n' - '\n' - 'It is a "SyntaxError" to use an "async for" statement outside ' - 'the body\n' - 'of a coroutine function.\n' - '\n' - '\n' - 'The "async with" statement\n' - '--------------------------\n' - '\n' - ' async_with_stmt ::= "async" with_stmt\n' - '\n' - 'An *asynchronous context manager* is a *context manager* that is ' - 'able\n' - 'to suspend execution in its *enter* and *exit* methods.\n' - '\n' - 'The following code:\n' - '\n' - ' async with EXPRESSION as TARGET:\n' - ' SUITE\n' - '\n' - 'is semantically equivalent to:\n' - '\n' - ' manager = (EXPRESSION)\n' - ' aenter = type(manager).__aenter__\n' - ' aexit = type(manager).__aexit__\n' - ' value = await aenter(manager)\n' - ' hit_except = False\n' - '\n' - ' try:\n' - ' TARGET = value\n' - ' SUITE\n' - ' except:\n' - ' hit_except = True\n' - ' if not await aexit(manager, *sys.exc_info()):\n' - ' raise\n' - ' finally:\n' - ' if not hit_except:\n' - ' await aexit(manager, None, None, None)\n' - '\n' - 'See also "__aenter__()" and "__aexit__()" for details.\n' - '\n' - 'It is a "SyntaxError" to use an "async with" statement outside ' - 'the\n' - 'body of a coroutine function.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 492** - Coroutines with async and await syntax\n' - ' The proposal that made coroutines a proper standalone ' - 'concept in\n' - ' Python, and added supporting syntax.\n' - '\n' - '\n' - 'Type parameter lists\n' - '====================\n' - '\n' - 'Added in version 3.12.\n' - '\n' - 'Changed in version 3.13: Support for default values was added ' - '(see\n' - '**PEP 696**).\n' - '\n' - ' type_params ::= "[" type_param ("," type_param)* "]"\n' - ' type_param ::= typevar | typevartuple | paramspec\n' - ' typevar ::= identifier (":" expression)? ("=" ' - 'expression)?\n' - ' typevartuple ::= "*" identifier ("=" expression)?\n' - ' paramspec ::= "**" identifier ("=" expression)?\n' - '\n' - 'Functions (including coroutines), classes and type aliases may ' - 'contain\n' - 'a type parameter list:\n' - '\n' - ' def max[T](args: list[T]) -> T:\n' - ' ...\n' - '\n' - ' async def amax[T](args: list[T]) -> T:\n' - ' ...\n' - '\n' - ' class Bag[T]:\n' - ' def __iter__(self) -> Iterator[T]:\n' - ' ...\n' - '\n' - ' def add(self, arg: T) -> None:\n' - ' ...\n' - '\n' - ' type ListOrSet[T] = list[T] | set[T]\n' - '\n' - 'Semantically, this indicates that the function, class, or type ' - 'alias\n' - 'is generic over a type variable. This information is primarily ' - 'used by\n' - 'static type checkers, and at runtime, generic objects behave ' - 'much like\n' - 'their non-generic counterparts.\n' - '\n' - 'Type parameters are declared in square brackets ("[]") ' - 'immediately\n' - 'after the name of the function, class, or type alias. The type\n' - 'parameters are accessible within the scope of the generic ' - 'object, but\n' - 'not elsewhere. Thus, after a declaration "def func[T](): pass", ' - 'the\n' - 'name "T" is not available in the module scope. Below, the ' - 'semantics of\n' - 'generic objects are described with more precision. The scope of ' - 'type\n' - 'parameters is modeled with a special function (technically, an\n' - 'annotation scope) that wraps the creation of the generic ' - 'object.\n' - '\n' - 'Generic functions, classes, and type aliases have a ' - '"__type_params__"\n' - 'attribute listing their type parameters.\n' - '\n' - 'Type parameters come in three kinds:\n' - '\n' - '* "typing.TypeVar", introduced by a plain name (e.g., "T").\n' - ' Semantically, this represents a single type to a type ' - 'checker.\n' - '\n' - '* "typing.TypeVarTuple", introduced by a name prefixed with a ' - 'single\n' - ' asterisk (e.g., "*Ts"). Semantically, this stands for a tuple ' - 'of any\n' - ' number of types.\n' - '\n' - '* "typing.ParamSpec", introduced by a name prefixed with two ' - 'asterisks\n' - ' (e.g., "**P"). Semantically, this stands for the parameters of ' - 'a\n' - ' callable.\n' - '\n' - '"typing.TypeVar" declarations can define *bounds* and ' - '*constraints*\n' - 'with a colon (":") followed by an expression. A single ' - 'expression\n' - 'after the colon indicates a bound (e.g. "T: int"). Semantically, ' - 'this\n' - 'means that the "typing.TypeVar" can only represent types that ' - 'are a\n' - 'subtype of this bound. A parenthesized tuple of expressions ' - 'after the\n' - 'colon indicates a set of constraints (e.g. "T: (str, bytes)"). ' - 'Each\n' - 'member of the tuple should be a type (again, this is not ' - 'enforced at\n' - 'runtime). Constrained type variables can only take on one of the ' - 'types\n' - 'in the list of constraints.\n' - '\n' - 'For "typing.TypeVar"s declared using the type parameter list ' - 'syntax,\n' - 'the bound and constraints are not evaluated when the generic ' - 'object is\n' - 'created, but only when the value is explicitly accessed through ' - 'the\n' - 'attributes "__bound__" and "__constraints__". To accomplish ' - 'this, the\n' - 'bounds or constraints are evaluated in a separate annotation ' - 'scope.\n' - '\n' - '"typing.TypeVarTuple"s and "typing.ParamSpec"s cannot have ' - 'bounds or\n' - 'constraints.\n' - '\n' - 'All three flavors of type parameters can also have a *default ' - 'value*,\n' - 'which is used when the type parameter is not explicitly ' - 'provided. This\n' - 'is added by appending a single equals sign ("=") followed by an\n' - 'expression. Like the bounds and constraints of type variables, ' - 'the\n' - 'default value is not evaluated when the object is created, but ' - 'only\n' - 'when the type parameter’s "__default__" attribute is accessed. ' - 'To this\n' - 'end, the default value is evaluated in a separate annotation ' - 'scope. If\n' - 'no default value is specified for a type parameter, the ' - '"__default__"\n' - 'attribute is set to the special sentinel object ' - '"typing.NoDefault".\n' - '\n' - 'The following example indicates the full set of allowed type ' - 'parameter\n' - 'declarations:\n' - '\n' - ' def overly_generic[\n' - ' SimpleTypeVar,\n' - ' TypeVarWithDefault = int,\n' - ' TypeVarWithBound: int,\n' - ' TypeVarWithConstraints: (str, bytes),\n' - ' *SimpleTypeVarTuple = (int, float),\n' - ' **SimpleParamSpec = (str, bytearray),\n' - ' ](\n' - ' a: SimpleTypeVar,\n' - ' b: TypeVarWithDefault,\n' - ' c: TypeVarWithBound,\n' - ' d: Callable[SimpleParamSpec, TypeVarWithConstraints],\n' - ' *e: SimpleTypeVarTuple,\n' - ' ): ...\n' - '\n' - '\n' - 'Generic functions\n' - '-----------------\n' - '\n' - 'Generic functions are declared as follows:\n' - '\n' - ' def func[T](arg: T): ...\n' - '\n' - 'This syntax is equivalent to:\n' - '\n' - ' annotation-def TYPE_PARAMS_OF_func():\n' - ' T = typing.TypeVar("T")\n' - ' def func(arg: T): ...\n' - ' func.__type_params__ = (T,)\n' - ' return func\n' - ' func = TYPE_PARAMS_OF_func()\n' - '\n' - 'Here "annotation-def" indicates an annotation scope, which is ' - 'not\n' - 'actually bound to any name at runtime. (One other liberty is ' - 'taken in\n' - 'the translation: the syntax does not go through attribute access ' - 'on\n' - 'the "typing" module, but creates an instance of ' - '"typing.TypeVar"\n' - 'directly.)\n' - '\n' - 'The annotations of generic functions are evaluated within the\n' - 'annotation scope used for declaring the type parameters, but ' - 'the\n' - 'function’s defaults and decorators are not.\n' - '\n' - 'The following example illustrates the scoping rules for these ' - 'cases,\n' - 'as well as for additional flavors of type parameters:\n' - '\n' - ' @decorator\n' - ' def func[T: int, *Ts, **P](*args: *Ts, arg: Callable[P, T] = ' - 'some_default):\n' - ' ...\n' - '\n' - 'Except for the lazy evaluation of the "TypeVar" bound, this is\n' - 'equivalent to:\n' - '\n' - ' DEFAULT_OF_arg = some_default\n' - '\n' - ' annotation-def TYPE_PARAMS_OF_func():\n' - '\n' - ' annotation-def BOUND_OF_T():\n' - ' return int\n' - ' # In reality, BOUND_OF_T() is evaluated only on demand.\n' - ' T = typing.TypeVar("T", bound=BOUND_OF_T())\n' - '\n' - ' Ts = typing.TypeVarTuple("Ts")\n' - ' P = typing.ParamSpec("P")\n' - '\n' - ' def func(*args: *Ts, arg: Callable[P, T] = ' - 'DEFAULT_OF_arg):\n' - ' ...\n' - '\n' - ' func.__type_params__ = (T, Ts, P)\n' - ' return func\n' - ' func = decorator(TYPE_PARAMS_OF_func())\n' - '\n' - 'The capitalized names like "DEFAULT_OF_arg" are not actually ' - 'bound at\n' - 'runtime.\n' - '\n' - '\n' - 'Generic classes\n' - '---------------\n' - '\n' - 'Generic classes are declared as follows:\n' - '\n' - ' class Bag[T]: ...\n' - '\n' - 'This syntax is equivalent to:\n' - '\n' - ' annotation-def TYPE_PARAMS_OF_Bag():\n' - ' T = typing.TypeVar("T")\n' - ' class Bag(typing.Generic[T]):\n' - ' __type_params__ = (T,)\n' - ' ...\n' - ' return Bag\n' - ' Bag = TYPE_PARAMS_OF_Bag()\n' - '\n' - 'Here again "annotation-def" (not a real keyword) indicates an\n' - 'annotation scope, and the name "TYPE_PARAMS_OF_Bag" is not ' - 'actually\n' - 'bound at runtime.\n' - '\n' - 'Generic classes implicitly inherit from "typing.Generic". The ' - 'base\n' - 'classes and keyword arguments of generic classes are evaluated ' - 'within\n' - 'the type scope for the type parameters, and decorators are ' - 'evaluated\n' - 'outside that scope. This is illustrated by this example:\n' - '\n' - ' @decorator\n' - ' class Bag(Base[T], arg=T): ...\n' - '\n' - 'This is equivalent to:\n' - '\n' - ' annotation-def TYPE_PARAMS_OF_Bag():\n' - ' T = typing.TypeVar("T")\n' - ' class Bag(Base[T], typing.Generic[T], arg=T):\n' - ' __type_params__ = (T,)\n' - ' ...\n' - ' return Bag\n' - ' Bag = decorator(TYPE_PARAMS_OF_Bag())\n' - '\n' - '\n' - 'Generic type aliases\n' - '--------------------\n' - '\n' - 'The "type" statement can also be used to create a generic type ' - 'alias:\n' - '\n' - ' type ListOrSet[T] = list[T] | set[T]\n' - '\n' - 'Except for the lazy evaluation of the value, this is equivalent ' - 'to:\n' - '\n' - ' annotation-def TYPE_PARAMS_OF_ListOrSet():\n' - ' T = typing.TypeVar("T")\n' - '\n' - ' annotation-def VALUE_OF_ListOrSet():\n' - ' return list[T] | set[T]\n' - ' # In reality, the value is lazily evaluated\n' - ' return typing.TypeAliasType("ListOrSet", ' - 'VALUE_OF_ListOrSet(), type_params=(T,))\n' - ' ListOrSet = TYPE_PARAMS_OF_ListOrSet()\n' - '\n' - 'Here, "annotation-def" (not a real keyword) indicates an ' - 'annotation\n' - 'scope. The capitalized names like "TYPE_PARAMS_OF_ListOrSet" are ' - 'not\n' - 'actually bound at runtime.\n' - '\n' - '\n' - 'Annotations\n' - '===========\n' - '\n' - 'Changed in version 3.14: Annotations are now lazily evaluated ' - 'by\n' - 'default.\n' - '\n' - 'Variables and function parameters may carry *annotations*, ' - 'created by\n' - 'adding a colon after the name, followed by an expression:\n' - '\n' - ' x: annotation = 1\n' - ' def f(param: annotation): ...\n' - '\n' - 'Functions may also carry a return annotation following an ' - 'arrow:\n' - '\n' - ' def f() -> annotation: ...\n' - '\n' - 'Annotations are conventionally used for *type hints*, but this ' - 'is not\n' - 'enforced by the language, and in general annotations may ' - 'contain\n' - 'arbitrary expressions. The presence of annotations does not ' - 'change the\n' - 'runtime semantics of the code, except if some mechanism is used ' - 'that\n' - 'introspects and uses the annotations (such as "dataclasses" or\n' - '"functools.singledispatch()").\n' - '\n' - 'By default, annotations are lazily evaluated in a annotation ' - 'scope.\n' - 'This means that they are not evaluated when the code containing ' - 'the\n' - 'annotation is evaluated. Instead, the interpreter saves ' - 'information\n' - 'that can be used to evaluate the annotation later if requested. ' - 'The\n' - '"annotationlib" module provides tools for evaluating ' - 'annotations.\n' - '\n' - 'If the future statement "from __future__ import annotations" is\n' - 'present, all annotations are instead stored as strings:\n' - '\n' - ' >>> from __future__ import annotations\n' - ' >>> def f(param: annotation): ...\n' - ' >>> f.__annotations__\n' - " {'param': 'annotation'}\n" - '\n' - '-[ Footnotes ]-\n' - '\n' - '[1] The exception is propagated to the invocation stack unless ' - 'there\n' - ' is a "finally" clause which happens to raise another ' - 'exception.\n' - ' That new exception causes the old one to be lost.\n' - '\n' - '[2] In pattern matching, a sequence is defined as one of the\n' - ' following:\n' - '\n' - ' * a class that inherits from "collections.abc.Sequence"\n' - '\n' - ' * a Python class that has been registered as\n' - ' "collections.abc.Sequence"\n' - '\n' - ' * a builtin class that has its (CPython) ' - '"Py_TPFLAGS_SEQUENCE" bit\n' - ' set\n' - '\n' - ' * a class that inherits from any of the above\n' - '\n' - ' The following standard library classes are sequences:\n' - '\n' - ' * "array.array"\n' - '\n' - ' * "collections.deque"\n' - '\n' - ' * "list"\n' - '\n' - ' * "memoryview"\n' - '\n' - ' * "range"\n' - '\n' - ' * "tuple"\n' - '\n' - ' Note:\n' - '\n' - ' Subject values of type "str", "bytes", and "bytearray" do ' - 'not\n' - ' match sequence patterns.\n' - '\n' - '[3] In pattern matching, a mapping is defined as one of the ' - 'following:\n' - '\n' - ' * a class that inherits from "collections.abc.Mapping"\n' - '\n' - ' * a Python class that has been registered as\n' - ' "collections.abc.Mapping"\n' - '\n' - ' * a builtin class that has its (CPython) ' - '"Py_TPFLAGS_MAPPING" bit\n' - ' set\n' - '\n' - ' * a class that inherits from any of the above\n' - '\n' - ' The standard library classes "dict" and ' - '"types.MappingProxyType"\n' - ' are mappings.\n' - '\n' - '[4] A string literal appearing as the first statement in the ' - 'function\n' - ' body is transformed into the function’s "__doc__" attribute ' - 'and\n' - ' therefore the function’s *docstring*.\n' - '\n' - '[5] A string literal appearing as the first statement in the ' - 'class\n' - ' body is transformed into the namespace’s "__doc__" item and\n' - ' therefore the class’s *docstring*.\n', - 'context-managers': 'With Statement Context Managers\n' - '*******************************\n' - '\n' - 'A *context manager* is an object that defines the ' - 'runtime context to\n' - 'be established when executing a "with" statement. The ' - 'context manager\n' - 'handles the entry into, and the exit from, the desired ' - 'runtime context\n' - 'for the execution of the block of code. Context ' - 'managers are normally\n' - 'invoked using the "with" statement (described in section ' - 'The with\n' - 'statement), but can also be used by directly invoking ' - 'their methods.\n' - '\n' - 'Typical uses of context managers include saving and ' - 'restoring various\n' - 'kinds of global state, locking and unlocking resources, ' - 'closing opened\n' - 'files, etc.\n' - '\n' - 'For more information on context managers, see Context ' - 'Manager Types.\n' - 'The "object" class itself does not provide the context ' - 'manager\n' - 'methods.\n' - '\n' - 'object.__enter__(self)\n' - '\n' - ' Enter the runtime context related to this object. The ' - '"with"\n' - ' statement will bind this method’s return value to the ' - 'target(s)\n' - ' specified in the "as" clause of the statement, if ' - 'any.\n' - '\n' - 'object.__exit__(self, exc_type, exc_value, traceback)\n' - '\n' - ' Exit the runtime context related to this object. The ' - 'parameters\n' - ' describe the exception that caused the context to be ' - 'exited. If the\n' - ' context was exited without an exception, all three ' - 'arguments will\n' - ' be "None".\n' - '\n' - ' If an exception is supplied, and the method wishes to ' - 'suppress the\n' - ' exception (i.e., prevent it from being propagated), ' - 'it should\n' - ' return a true value. Otherwise, the exception will be ' - 'processed\n' - ' normally upon exit from this method.\n' - '\n' - ' Note that "__exit__()" methods should not reraise the ' - 'passed-in\n' - ' exception; this is the caller’s responsibility.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 343** - The “with” statement\n' - ' The specification, background, and examples for the ' - 'Python "with"\n' - ' statement.\n', - 'continue': 'The "continue" statement\n' - '************************\n' - '\n' - ' continue_stmt ::= "continue"\n' - '\n' - '"continue" may only occur syntactically nested in a "for" or ' - '"while"\n' - 'loop, but not nested in a function or class definition within ' - 'that\n' - 'loop. It continues with the next cycle of the nearest enclosing ' - 'loop.\n' - '\n' - 'When "continue" passes control out of a "try" statement with a\n' - '"finally" clause, that "finally" clause is executed before ' - 'really\n' - 'starting the next loop cycle.\n', - 'conversions': 'Arithmetic conversions\n' - '**********************\n' - '\n' - 'When a description of an arithmetic operator below uses the ' - 'phrase\n' - '“the numeric arguments are converted to a common real type”, ' - 'this\n' - 'means that the operator implementation for built-in types ' - 'works as\n' - 'follows:\n' - '\n' - '* If both arguments are complex numbers, no conversion is ' - 'performed;\n' - '\n' - '* if either argument is a complex or a floating-point number, ' - 'the\n' - ' other is converted to a floating-point number;\n' - '\n' - '* otherwise, both must be integers and no conversion is ' - 'necessary.\n' - '\n' - 'Some additional rules apply for certain operators (e.g., a ' - 'string as a\n' - 'left argument to the ‘%’ operator). Extensions must define ' - 'their own\n' - 'conversion behavior.\n', - 'customization': 'Basic customization\n' - '*******************\n' - '\n' - 'object.__new__(cls[, ...])\n' - '\n' - ' Called to create a new instance of class *cls*. ' - '"__new__()" is a\n' - ' static method (special-cased so you need not declare it ' - 'as such)\n' - ' that takes the class of which an instance was requested ' - 'as its\n' - ' first argument. The remaining arguments are those ' - 'passed to the\n' - ' object constructor expression (the call to the class). ' - 'The return\n' - ' value of "__new__()" should be the new object instance ' - '(usually an\n' - ' instance of *cls*).\n' - '\n' - ' Typical implementations create a new instance of the ' - 'class by\n' - ' invoking the superclass’s "__new__()" method using\n' - ' "super().__new__(cls[, ...])" with appropriate arguments ' - 'and then\n' - ' modifying the newly created instance as necessary before ' - 'returning\n' - ' it.\n' - '\n' - ' If "__new__()" is invoked during object construction and ' - 'it returns\n' - ' an instance of *cls*, then the new instance’s ' - '"__init__()" method\n' - ' will be invoked like "__init__(self[, ...])", where ' - '*self* is the\n' - ' new instance and the remaining arguments are the same as ' - 'were\n' - ' passed to the object constructor.\n' - '\n' - ' If "__new__()" does not return an instance of *cls*, ' - 'then the new\n' - ' instance’s "__init__()" method will not be invoked.\n' - '\n' - ' "__new__()" is intended mainly to allow subclasses of ' - 'immutable\n' - ' types (like int, str, or tuple) to customize instance ' - 'creation. It\n' - ' is also commonly overridden in custom metaclasses in ' - 'order to\n' - ' customize class creation.\n' - '\n' - 'object.__init__(self[, ...])\n' - '\n' - ' Called after the instance has been created (by ' - '"__new__()"), but\n' - ' before it is returned to the caller. The arguments are ' - 'those\n' - ' passed to the class constructor expression. If a base ' - 'class has an\n' - ' "__init__()" method, the derived class’s "__init__()" ' - 'method, if\n' - ' any, must explicitly call it to ensure proper ' - 'initialization of the\n' - ' base class part of the instance; for example:\n' - ' "super().__init__([args...])".\n' - '\n' - ' Because "__new__()" and "__init__()" work together in ' - 'constructing\n' - ' objects ("__new__()" to create it, and "__init__()" to ' - 'customize\n' - ' it), no non-"None" value may be returned by ' - '"__init__()"; doing so\n' - ' will cause a "TypeError" to be raised at runtime.\n' - '\n' - 'object.__del__(self)\n' - '\n' - ' Called when the instance is about to be destroyed. This ' - 'is also\n' - ' called a finalizer or (improperly) a destructor. If a ' - 'base class\n' - ' has a "__del__()" method, the derived class’s ' - '"__del__()" method,\n' - ' if any, must explicitly call it to ensure proper ' - 'deletion of the\n' - ' base class part of the instance.\n' - '\n' - ' It is possible (though not recommended!) for the ' - '"__del__()" method\n' - ' to postpone destruction of the instance by creating a ' - 'new reference\n' - ' to it. This is called object *resurrection*. It is\n' - ' implementation-dependent whether "__del__()" is called a ' - 'second\n' - ' time when a resurrected object is about to be destroyed; ' - 'the\n' - ' current *CPython* implementation only calls it once.\n' - '\n' - ' It is not guaranteed that "__del__()" methods are called ' - 'for\n' - ' objects that still exist when the interpreter exits.\n' - ' "weakref.finalize" provides a straightforward way to ' - 'register a\n' - ' cleanup function to be called when an object is garbage ' - 'collected.\n' - '\n' - ' Note:\n' - '\n' - ' "del x" doesn’t directly call "x.__del__()" — the ' - 'former\n' - ' decrements the reference count for "x" by one, and the ' - 'latter is\n' - ' only called when "x"’s reference count reaches zero.\n' - '\n' - ' **CPython implementation detail:** It is possible for a ' - 'reference\n' - ' cycle to prevent the reference count of an object from ' - 'going to\n' - ' zero. In this case, the cycle will be later detected ' - 'and deleted\n' - ' by the *cyclic garbage collector*. A common cause of ' - 'reference\n' - ' cycles is when an exception has been caught in a local ' - 'variable.\n' - ' The frame’s locals then reference the exception, which ' - 'references\n' - ' its own traceback, which references the locals of all ' - 'frames caught\n' - ' in the traceback.\n' - '\n' - ' See also: Documentation for the "gc" module.\n' - '\n' - ' Warning:\n' - '\n' - ' Due to the precarious circumstances under which ' - '"__del__()"\n' - ' methods are invoked, exceptions that occur during ' - 'their execution\n' - ' are ignored, and a warning is printed to "sys.stderr" ' - 'instead.\n' - ' In particular:\n' - '\n' - ' * "__del__()" can be invoked when arbitrary code is ' - 'being\n' - ' executed, including from any arbitrary thread. If ' - '"__del__()"\n' - ' needs to take a lock or invoke any other blocking ' - 'resource, it\n' - ' may deadlock as the resource may already be taken by ' - 'the code\n' - ' that gets interrupted to execute "__del__()".\n' - '\n' - ' * "__del__()" can be executed during interpreter ' - 'shutdown. As a\n' - ' consequence, the global variables it needs to access ' - '(including\n' - ' other modules) may already have been deleted or set ' - 'to "None".\n' - ' Python guarantees that globals whose name begins ' - 'with a single\n' - ' underscore are deleted from their module before ' - 'other globals\n' - ' are deleted; if no other references to such globals ' - 'exist, this\n' - ' may help in assuring that imported modules are still ' - 'available\n' - ' at the time when the "__del__()" method is called.\n' - '\n' - 'object.__repr__(self)\n' - '\n' - ' Called by the "repr()" built-in function to compute the ' - '“official”\n' - ' string representation of an object. If at all possible, ' - 'this\n' - ' should look like a valid Python expression that could be ' - 'used to\n' - ' recreate an object with the same value (given an ' - 'appropriate\n' - ' environment). If this is not possible, a string of the ' - 'form\n' - ' "<...some useful description...>" should be returned. ' - 'The return\n' - ' value must be a string object. If a class defines ' - '"__repr__()" but\n' - ' not "__str__()", then "__repr__()" is also used when an ' - '“informal”\n' - ' string representation of instances of that class is ' - 'required.\n' - '\n' - ' This is typically used for debugging, so it is important ' - 'that the\n' - ' representation is information-rich and unambiguous. A ' - 'default\n' - ' implementation is provided by the "object" class ' - 'itself.\n' - '\n' - 'object.__str__(self)\n' - '\n' - ' Called by "str(object)", the default "__format__()" ' - 'implementation,\n' - ' and the built-in function "print()", to compute the ' - '“informal” or\n' - ' nicely printable string representation of an object. ' - 'The return\n' - ' value must be a str object.\n' - '\n' - ' This method differs from "object.__repr__()" in that ' - 'there is no\n' - ' expectation that "__str__()" return a valid Python ' - 'expression: a\n' - ' more convenient or concise representation can be used.\n' - '\n' - ' The default implementation defined by the built-in type ' - '"object"\n' - ' calls "object.__repr__()".\n' - '\n' - 'object.__bytes__(self)\n' - '\n' - ' Called by bytes to compute a byte-string representation ' - 'of an\n' - ' object. This should return a "bytes" object. The ' - '"object" class\n' - ' itself does not provide this method.\n' - '\n' - 'object.__format__(self, format_spec)\n' - '\n' - ' Called by the "format()" built-in function, and by ' - 'extension,\n' - ' evaluation of formatted string literals and the ' - '"str.format()"\n' - ' method, to produce a “formatted” string representation ' - 'of an\n' - ' object. The *format_spec* argument is a string that ' - 'contains a\n' - ' description of the formatting options desired. The ' - 'interpretation\n' - ' of the *format_spec* argument is up to the type ' - 'implementing\n' - ' "__format__()", however most classes will either ' - 'delegate\n' - ' formatting to one of the built-in types, or use a ' - 'similar\n' - ' formatting option syntax.\n' - '\n' - ' See Format Specification Mini-Language for a description ' - 'of the\n' - ' standard formatting syntax.\n' - '\n' - ' The return value must be a string object.\n' - '\n' - ' The default implementation by the "object" class should ' - 'be given an\n' - ' empty *format_spec* string. It delegates to ' - '"__str__()".\n' - '\n' - ' Changed in version 3.4: The __format__ method of ' - '"object" itself\n' - ' raises a "TypeError" if passed any non-empty string.\n' - '\n' - ' Changed in version 3.7: "object.__format__(x, \'\')" is ' - 'now\n' - ' equivalent to "str(x)" rather than "format(str(x), ' - '\'\')".\n' - '\n' - 'object.__lt__(self, other)\n' - 'object.__le__(self, other)\n' - 'object.__eq__(self, other)\n' - 'object.__ne__(self, other)\n' - 'object.__gt__(self, other)\n' - 'object.__ge__(self, other)\n' - '\n' - ' These are the so-called “rich comparison” methods. The\n' - ' correspondence between operator symbols and method names ' - 'is as\n' - ' follows: "x<y" calls "x.__lt__(y)", "x<=y" calls ' - '"x.__le__(y)",\n' - ' "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", ' - '"x>y" calls\n' - ' "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)".\n' - '\n' - ' A rich comparison method may return the singleton ' - '"NotImplemented"\n' - ' if it does not implement the operation for a given pair ' - 'of\n' - ' arguments. By convention, "False" and "True" are ' - 'returned for a\n' - ' successful comparison. However, these methods can return ' - 'any value,\n' - ' so if the comparison operator is used in a Boolean ' - 'context (e.g.,\n' - ' in the condition of an "if" statement), Python will call ' - '"bool()"\n' - ' on the value to determine if the result is true or ' - 'false.\n' - '\n' - ' By default, "object" implements "__eq__()" by using ' - '"is", returning\n' - ' "NotImplemented" in the case of a false comparison: ' - '"True if x is y\n' - ' else NotImplemented". For "__ne__()", by default it ' - 'delegates to\n' - ' "__eq__()" and inverts the result unless it is ' - '"NotImplemented".\n' - ' There are no other implied relationships among the ' - 'comparison\n' - ' operators or default implementations; for example, the ' - 'truth of\n' - ' "(x<y or x==y)" does not imply "x<=y". To automatically ' - 'generate\n' - ' ordering operations from a single root operation, see\n' - ' "functools.total_ordering()".\n' - '\n' - ' By default, the "object" class provides implementations ' - 'consistent\n' - ' with Value comparisons: equality compares according to ' - 'object\n' - ' identity, and order comparisons raise "TypeError". Each ' - 'default\n' - ' method may generate these results directly, but may also ' - 'return\n' - ' "NotImplemented".\n' - '\n' - ' See the paragraph on "__hash__()" for some important ' - 'notes on\n' - ' creating *hashable* objects which support custom ' - 'comparison\n' - ' operations and are usable as dictionary keys.\n' - '\n' - ' There are no swapped-argument versions of these methods ' - '(to be used\n' - ' when the left argument does not support the operation ' - 'but the right\n' - ' argument does); rather, "__lt__()" and "__gt__()" are ' - 'each other’s\n' - ' reflection, "__le__()" and "__ge__()" are each other’s ' - 'reflection,\n' - ' and "__eq__()" and "__ne__()" are their own reflection. ' - 'If the\n' - ' operands are of different types, and the right operand’s ' - 'type is a\n' - ' direct or indirect subclass of the left operand’s type, ' - 'the\n' - ' reflected method of the right operand has priority, ' - 'otherwise the\n' - ' left operand’s method has priority. Virtual subclassing ' - 'is not\n' - ' considered.\n' - '\n' - ' When no appropriate method returns any value other than\n' - ' "NotImplemented", the "==" and "!=" operators will fall ' - 'back to\n' - ' "is" and "is not", respectively.\n' - '\n' - 'object.__hash__(self)\n' - '\n' - ' Called by built-in function "hash()" and for operations ' - 'on members\n' - ' of hashed collections including "set", "frozenset", and ' - '"dict".\n' - ' The "__hash__()" method should return an integer. The ' - 'only required\n' - ' property is that objects which compare equal have the ' - 'same hash\n' - ' value; it is advised to mix together the hash values of ' - 'the\n' - ' components of the object that also play a part in ' - 'comparison of\n' - ' objects by packing them into a tuple and hashing the ' - 'tuple.\n' - ' Example:\n' - '\n' - ' def __hash__(self):\n' - ' return hash((self.name, self.nick, self.color))\n' - '\n' - ' Note:\n' - '\n' - ' "hash()" truncates the value returned from an object’s ' - 'custom\n' - ' "__hash__()" method to the size of a "Py_ssize_t". ' - 'This is\n' - ' typically 8 bytes on 64-bit builds and 4 bytes on ' - '32-bit builds.\n' - ' If an object’s "__hash__()" must interoperate on ' - 'builds of\n' - ' different bit sizes, be sure to check the width on all ' - 'supported\n' - ' builds. An easy way to do this is with "python -c ' - '"import sys;\n' - ' print(sys.hash_info.width)"".\n' - '\n' - ' If a class does not define an "__eq__()" method it ' - 'should not\n' - ' define a "__hash__()" operation either; if it defines ' - '"__eq__()"\n' - ' but not "__hash__()", its instances will not be usable ' - 'as items in\n' - ' hashable collections. If a class defines mutable ' - 'objects and\n' - ' implements an "__eq__()" method, it should not ' - 'implement\n' - ' "__hash__()", since the implementation of *hashable* ' - 'collections\n' - ' requires that a key’s hash value is immutable (if the ' - 'object’s hash\n' - ' value changes, it will be in the wrong hash bucket).\n' - '\n' - ' User-defined classes have "__eq__()" and "__hash__()" ' - 'methods by\n' - ' default (inherited from the "object" class); with them, ' - 'all objects\n' - ' compare unequal (except with themselves) and ' - '"x.__hash__()" returns\n' - ' an appropriate value such that "x == y" implies both ' - 'that "x is y"\n' - ' and "hash(x) == hash(y)".\n' - '\n' - ' A class that overrides "__eq__()" and does not define ' - '"__hash__()"\n' - ' will have its "__hash__()" implicitly set to "None". ' - 'When the\n' - ' "__hash__()" method of a class is "None", instances of ' - 'the class\n' - ' will raise an appropriate "TypeError" when a program ' - 'attempts to\n' - ' retrieve their hash value, and will also be correctly ' - 'identified as\n' - ' unhashable when checking "isinstance(obj,\n' - ' collections.abc.Hashable)".\n' - '\n' - ' If a class that overrides "__eq__()" needs to retain ' - 'the\n' - ' implementation of "__hash__()" from a parent class, the ' - 'interpreter\n' - ' must be told this explicitly by setting "__hash__ =\n' - ' <ParentClass>.__hash__".\n' - '\n' - ' If a class that does not override "__eq__()" wishes to ' - 'suppress\n' - ' hash support, it should include "__hash__ = None" in the ' - 'class\n' - ' definition. A class which defines its own "__hash__()" ' - 'that\n' - ' explicitly raises a "TypeError" would be incorrectly ' - 'identified as\n' - ' hashable by an "isinstance(obj, ' - 'collections.abc.Hashable)" call.\n' - '\n' - ' Note:\n' - '\n' - ' By default, the "__hash__()" values of str and bytes ' - 'objects are\n' - ' “salted” with an unpredictable random value. Although ' - 'they\n' - ' remain constant within an individual Python process, ' - 'they are not\n' - ' predictable between repeated invocations of ' - 'Python.This is\n' - ' intended to provide protection against a ' - 'denial-of-service caused\n' - ' by carefully chosen inputs that exploit the worst ' - 'case\n' - ' performance of a dict insertion, *O*(*n*^2) ' - 'complexity. See\n' - ' http://ocert.org/advisories/ocert-2011-003.html for\n' - ' details.Changing hash values affects the iteration ' - 'order of sets.\n' - ' Python has never made guarantees about this ordering ' - '(and it\n' - ' typically varies between 32-bit and 64-bit builds).See ' - 'also\n' - ' "PYTHONHASHSEED".\n' - '\n' - ' Changed in version 3.3: Hash randomization is enabled by ' - 'default.\n' - '\n' - 'object.__bool__(self)\n' - '\n' - ' Called to implement truth value testing and the built-in ' - 'operation\n' - ' "bool()"; should return "False" or "True". When this ' - 'method is not\n' - ' defined, "__len__()" is called, if it is defined, and ' - 'the object is\n' - ' considered true if its result is nonzero. If a class ' - 'defines\n' - ' neither "__len__()" nor "__bool__()" (which is true of ' - 'the "object"\n' - ' class itself), all its instances are considered true.\n', - 'debugger': '"pdb" — The Python Debugger\n' - '***************************\n' - '\n' - '**Source code:** Lib/pdb.py\n' - '\n' - '======================================================================\n' - '\n' - 'The module "pdb" defines an interactive source code debugger ' - 'for\n' - 'Python programs. It supports setting (conditional) breakpoints ' - 'and\n' - 'single stepping at the source line level, inspection of stack ' - 'frames,\n' - 'source code listing, and evaluation of arbitrary Python code in ' - 'the\n' - 'context of any stack frame. It also supports post-mortem ' - 'debugging\n' - 'and can be called under program control.\n' - '\n' - 'The debugger is extensible – it is actually defined as the ' - 'class\n' - '"Pdb". This is currently undocumented but easily understood by ' - 'reading\n' - 'the source. The extension interface uses the modules "bdb" and ' - '"cmd".\n' - '\n' - 'See also:\n' - '\n' - ' Module "faulthandler"\n' - ' Used to dump Python tracebacks explicitly, on a fault, ' - 'after a\n' - ' timeout, or on a user signal.\n' - '\n' - ' Module "traceback"\n' - ' Standard interface to extract, format and print stack ' - 'traces of\n' - ' Python programs.\n' - '\n' - 'The typical usage to break into the debugger is to insert:\n' - '\n' - ' import pdb; pdb.set_trace()\n' - '\n' - 'Or:\n' - '\n' - ' breakpoint()\n' - '\n' - 'at the location you want to break into the debugger, and then ' - 'run the\n' - 'program. You can then step through the code following this ' - 'statement,\n' - 'and continue running without the debugger using the "continue"\n' - 'command.\n' - '\n' - 'Changed in version 3.7: The built-in "breakpoint()", when called ' - 'with\n' - 'defaults, can be used instead of "import pdb; pdb.set_trace()".\n' - '\n' - ' def double(x):\n' - ' breakpoint()\n' - ' return x * 2\n' - ' val = 3\n' - ' print(f"{val} * 2 is {double(val)}")\n' - '\n' - 'The debugger’s prompt is "(Pdb)", which is the indicator that ' - 'you are\n' - 'in debug mode:\n' - '\n' - ' > ...(2)double()\n' - ' -> breakpoint()\n' - ' (Pdb) p x\n' - ' 3\n' - ' (Pdb) continue\n' - ' 3 * 2 is 6\n' - '\n' - 'Changed in version 3.3: Tab-completion via the "readline" module ' - 'is\n' - 'available for commands and command arguments, e.g. the current ' - 'global\n' - 'and local names are offered as arguments of the "p" command.\n' - '\n' - 'You can also invoke "pdb" from the command line to debug other\n' - 'scripts. For example:\n' - '\n' - ' python -m pdb myscript.py\n' - '\n' - 'When invoked as a module, pdb will automatically enter ' - 'post-mortem\n' - 'debugging if the program being debugged exits abnormally. After ' - 'post-\n' - 'mortem debugging (or after normal exit of the program), pdb ' - 'will\n' - 'restart the program. Automatic restarting preserves pdb’s state ' - '(such\n' - 'as breakpoints) and in most cases is more useful than quitting ' - 'the\n' - 'debugger upon program’s exit.\n' - '\n' - 'Changed in version 3.2: Added the "-c" option to execute ' - 'commands as\n' - 'if given in a ".pdbrc" file; see Debugger Commands.\n' - '\n' - 'Changed in version 3.7: Added the "-m" option to execute ' - 'modules\n' - 'similar to the way "python -m" does. As with a script, the ' - 'debugger\n' - 'will pause execution just before the first line of the module.\n' - '\n' - 'Typical usage to execute a statement under control of the ' - 'debugger is:\n' - '\n' - ' >>> import pdb\n' - ' >>> def f(x):\n' - ' ... print(1 / x)\n' - ' >>> pdb.run("f(2)")\n' - ' > <string>(1)<module>()\n' - ' (Pdb) continue\n' - ' 0.5\n' - ' >>>\n' - '\n' - 'The typical usage to inspect a crashed program is:\n' - '\n' - ' >>> import pdb\n' - ' >>> def f(x):\n' - ' ... print(1 / x)\n' - ' ...\n' - ' >>> f(0)\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 1, in <module>\n' - ' File "<stdin>", line 2, in f\n' - ' ZeroDivisionError: division by zero\n' - ' >>> pdb.pm()\n' - ' > <stdin>(2)f()\n' - ' (Pdb) p x\n' - ' 0\n' - ' (Pdb)\n' - '\n' - 'Changed in version 3.13: The implementation of **PEP 667** means ' - 'that\n' - 'name assignments made via "pdb" will immediately affect the ' - 'active\n' - 'scope, even when running inside an *optimized scope*.\n' - '\n' - 'The module defines the following functions; each enters the ' - 'debugger\n' - 'in a slightly different way:\n' - '\n' - 'pdb.run(statement, globals=None, locals=None)\n' - '\n' - ' Execute the *statement* (given as a string or a code object) ' - 'under\n' - ' debugger control. The debugger prompt appears before any ' - 'code is\n' - ' executed; you can set breakpoints and type "continue", or you ' - 'can\n' - ' step through the statement using "step" or "next" (all these\n' - ' commands are explained below). The optional *globals* and ' - '*locals*\n' - ' arguments specify the environment in which the code is ' - 'executed; by\n' - ' default the dictionary of the module "__main__" is used. ' - '(See the\n' - ' explanation of the built-in "exec()" or "eval()" functions.)\n' - '\n' - 'pdb.runeval(expression, globals=None, locals=None)\n' - '\n' - ' Evaluate the *expression* (given as a string or a code ' - 'object)\n' - ' under debugger control. When "runeval()" returns, it returns ' - 'the\n' - ' value of the *expression*. Otherwise this function is ' - 'similar to\n' - ' "run()".\n' - '\n' - 'pdb.runcall(function, *args, **kwds)\n' - '\n' - ' Call the *function* (a function or method object, not a ' - 'string)\n' - ' with the given arguments. When "runcall()" returns, it ' - 'returns\n' - ' whatever the function call returned. The debugger prompt ' - 'appears\n' - ' as soon as the function is entered.\n' - '\n' - 'pdb.set_trace(*, header=None, commands=None)\n' - '\n' - ' Enter the debugger at the calling stack frame. This is ' - 'useful to\n' - ' hard-code a breakpoint at a given point in a program, even if ' - 'the\n' - ' code is not otherwise being debugged (e.g. when an assertion\n' - ' fails). If given, *header* is printed to the console just ' - 'before\n' - ' debugging begins. The *commands* argument, if given, is a ' - 'list of\n' - ' commands to execute when the debugger starts.\n' - '\n' - ' Changed in version 3.7: The keyword-only argument *header*.\n' - '\n' - ' Changed in version 3.13: "set_trace()" will enter the ' - 'debugger\n' - ' immediately, rather than on the next line of code to be ' - 'executed.\n' - '\n' - ' Added in version 3.14: The *commands* argument.\n' - '\n' - 'pdb.post_mortem(t=None)\n' - '\n' - ' Enter post-mortem debugging of the given exception or ' - 'traceback\n' - ' object. If no value is given, it uses the exception that is\n' - ' currently being handled, or raises "ValueError" if there ' - 'isn’t one.\n' - '\n' - ' Changed in version 3.13: Support for exception objects was ' - 'added.\n' - '\n' - 'pdb.pm()\n' - '\n' - ' Enter post-mortem debugging of the exception found in\n' - ' "sys.last_exc".\n' - '\n' - 'The "run*" functions and "set_trace()" are aliases for ' - 'instantiating\n' - 'the "Pdb" class and calling the method of the same name. If you ' - 'want\n' - 'to access further features, you have to do this yourself:\n' - '\n' - "class pdb.Pdb(completekey='tab', stdin=None, stdout=None, " - 'skip=None, nosigint=False, readrc=True, mode=None)\n' - '\n' - ' "Pdb" is the debugger class.\n' - '\n' - ' The *completekey*, *stdin* and *stdout* arguments are passed ' - 'to the\n' - ' underlying "cmd.Cmd" class; see the description there.\n' - '\n' - ' The *skip* argument, if given, must be an iterable of ' - 'glob-style\n' - ' module name patterns. The debugger will not step into frames ' - 'that\n' - ' originate in a module that matches one of these patterns. ' - '[1]\n' - '\n' - ' By default, Pdb sets a handler for the SIGINT signal (which ' - 'is sent\n' - ' when the user presses "Ctrl-C" on the console) when you give ' - 'a\n' - ' "continue" command. This allows you to break into the ' - 'debugger\n' - ' again by pressing "Ctrl-C". If you want Pdb not to touch ' - 'the\n' - ' SIGINT handler, set *nosigint* to true.\n' - '\n' - ' The *readrc* argument defaults to true and controls whether ' - 'Pdb\n' - ' will load .pdbrc files from the filesystem.\n' - '\n' - ' The *mode* argument specifies how the debugger was invoked. ' - 'It\n' - ' impacts the workings of some debugger commands. Valid values ' - 'are\n' - ' "\'inline\'" (used by the breakpoint() builtin), "\'cli\'" ' - '(used by the\n' - ' command line invocation) or "None" (for backwards compatible\n' - ' behaviour, as before the *mode* argument was added).\n' - '\n' - ' Example call to enable tracing with *skip*:\n' - '\n' - " import pdb; pdb.Pdb(skip=['django.*']).set_trace()\n" - '\n' - ' Raises an auditing event "pdb.Pdb" with no arguments.\n' - '\n' - ' Changed in version 3.1: Added the *skip* parameter.\n' - '\n' - ' Changed in version 3.2: Added the *nosigint* parameter. ' - 'Previously,\n' - ' a SIGINT handler was never set by Pdb.\n' - '\n' - ' Changed in version 3.6: The *readrc* argument.\n' - '\n' - ' Added in version 3.14: Added the *mode* argument.\n' - '\n' - ' run(statement, globals=None, locals=None)\n' - ' runeval(expression, globals=None, locals=None)\n' - ' runcall(function, *args, **kwds)\n' - ' set_trace()\n' - '\n' - ' See the documentation for the functions explained above.\n' - '\n' - '\n' - 'Debugger Commands\n' - '=================\n' - '\n' - 'The commands recognized by the debugger are listed below. Most\n' - 'commands can be abbreviated to one or two letters as indicated; ' - 'e.g.\n' - '"h(elp)" means that either "h" or "help" can be used to enter ' - 'the help\n' - 'command (but not "he" or "hel", nor "H" or "Help" or "HELP").\n' - 'Arguments to commands must be separated by whitespace (spaces ' - 'or\n' - 'tabs). Optional arguments are enclosed in square brackets ' - '("[]") in\n' - 'the command syntax; the square brackets must not be typed.\n' - 'Alternatives in the command syntax are separated by a vertical ' - 'bar\n' - '("|").\n' - '\n' - 'Entering a blank line repeats the last command entered. ' - 'Exception: if\n' - 'the last command was a "list" command, the next 11 lines are ' - 'listed.\n' - '\n' - 'Commands that the debugger doesn’t recognize are assumed to be ' - 'Python\n' - 'statements and are executed in the context of the program being\n' - 'debugged. Python statements can also be prefixed with an ' - 'exclamation\n' - 'point ("!"). This is a powerful way to inspect the program ' - 'being\n' - 'debugged; it is even possible to change a variable or call a ' - 'function.\n' - 'When an exception occurs in such a statement, the exception name ' - 'is\n' - 'printed but the debugger’s state is not changed.\n' - '\n' - 'Changed in version 3.13: Expressions/Statements whose prefix is ' - 'a pdb\n' - 'command are now correctly identified and executed.\n' - '\n' - 'The debugger supports aliases. Aliases can have parameters ' - 'which\n' - 'allows one a certain level of adaptability to the context under\n' - 'examination.\n' - '\n' - 'Multiple commands may be entered on a single line, separated by ' - '";;".\n' - '(A single ";" is not used as it is the separator for multiple ' - 'commands\n' - 'in a line that is passed to the Python parser.) No intelligence ' - 'is\n' - 'applied to separating the commands; the input is split at the ' - 'first\n' - '";;" pair, even if it is in the middle of a quoted string. A\n' - 'workaround for strings with double semicolons is to use ' - 'implicit\n' - 'string concatenation "\';\'\';\'" or "";"";"".\n' - '\n' - 'To set a temporary global variable, use a *convenience ' - 'variable*. A\n' - '*convenience variable* is a variable whose name starts with ' - '"$". For\n' - 'example, "$foo = 1" sets a global variable "$foo" which you can ' - 'use in\n' - 'the debugger session. The *convenience variables* are cleared ' - 'when\n' - 'the program resumes execution so it’s less likely to interfere ' - 'with\n' - 'your program compared to using normal variables like "foo = 1".\n' - '\n' - 'There are three preset *convenience variables*:\n' - '\n' - '* "$_frame": the current frame you are debugging\n' - '\n' - '* "$_retval": the return value if the frame is returning\n' - '\n' - '* "$_exception": the exception if the frame is raising an ' - 'exception\n' - '\n' - 'Added in version 3.12: Added the *convenience variable* ' - 'feature.\n' - '\n' - 'If a file ".pdbrc" exists in the user’s home directory or in ' - 'the\n' - 'current directory, it is read with "\'utf-8\'" encoding and ' - 'executed as\n' - 'if it had been typed at the debugger prompt, with the exception ' - 'that\n' - 'empty lines and lines starting with "#" are ignored. This is\n' - 'particularly useful for aliases. If both files exist, the one ' - 'in the\n' - 'home directory is read first and aliases defined there can be\n' - 'overridden by the local file.\n' - '\n' - 'Changed in version 3.2: ".pdbrc" can now contain commands that\n' - 'continue debugging, such as "continue" or "next". Previously, ' - 'these\n' - 'commands had no effect.\n' - '\n' - 'Changed in version 3.11: ".pdbrc" is now read with "\'utf-8\'" ' - 'encoding.\n' - 'Previously, it was read with the system locale encoding.\n' - '\n' - 'h(elp) [command]\n' - '\n' - ' Without argument, print the list of available commands. With ' - 'a\n' - ' *command* as argument, print help about that command. "help ' - 'pdb"\n' - ' displays the full documentation (the docstring of the "pdb"\n' - ' module). Since the *command* argument must be an identifier, ' - '"help\n' - ' exec" must be entered to get help on the "!" command.\n' - '\n' - 'w(here) [count]\n' - '\n' - ' Print a stack trace, with the most recent frame at the ' - 'bottom. if\n' - ' *count* is 0, print the current frame entry. If *count* is\n' - ' negative, print the least recent - *count* frames. If *count* ' - 'is\n' - ' positive, print the most recent *count* frames. An arrow ' - '(">")\n' - ' indicates the current frame, which determines the context of ' - 'most\n' - ' commands.\n' - '\n' - ' Changed in version 3.14: *count* argument is added.\n' - '\n' - 'd(own) [count]\n' - '\n' - ' Move the current frame *count* (default one) levels down in ' - 'the\n' - ' stack trace (to a newer frame).\n' - '\n' - 'u(p) [count]\n' - '\n' - ' Move the current frame *count* (default one) levels up in the ' - 'stack\n' - ' trace (to an older frame).\n' - '\n' - 'b(reak) [([filename:]lineno | function) [, condition]]\n' - '\n' - ' With a *lineno* argument, set a break at line *lineno* in ' - 'the\n' - ' current file. The line number may be prefixed with a ' - '*filename* and\n' - ' a colon, to specify a breakpoint in another file (possibly ' - 'one that\n' - ' hasn’t been loaded yet). The file is searched on ' - '"sys.path".\n' - ' Acceptable forms of *filename* are "/abspath/to/file.py",\n' - ' "relpath/file.py", "module" and "package.module".\n' - '\n' - ' With a *function* argument, set a break at the first ' - 'executable\n' - ' statement within that function. *function* can be any ' - 'expression\n' - ' that evaluates to a function in the current namespace.\n' - '\n' - ' If a second argument is present, it is an expression which ' - 'must\n' - ' evaluate to true before the breakpoint is honored.\n' - '\n' - ' Without argument, list all breaks, including for each ' - 'breakpoint,\n' - ' the number of times that breakpoint has been hit, the ' - 'current\n' - ' ignore count, and the associated condition if any.\n' - '\n' - ' Each breakpoint is assigned a number to which all the other\n' - ' breakpoint commands refer.\n' - '\n' - 'tbreak [([filename:]lineno | function) [, condition]]\n' - '\n' - ' Temporary breakpoint, which is removed automatically when it ' - 'is\n' - ' first hit. The arguments are the same as for "break".\n' - '\n' - 'cl(ear) [filename:lineno | bpnumber ...]\n' - '\n' - ' With a *filename:lineno* argument, clear all the breakpoints ' - 'at\n' - ' this line. With a space separated list of breakpoint numbers, ' - 'clear\n' - ' those breakpoints. Without argument, clear all breaks (but ' - 'first\n' - ' ask confirmation).\n' - '\n' - 'disable bpnumber [bpnumber ...]\n' - '\n' - ' Disable the breakpoints given as a space separated list of\n' - ' breakpoint numbers. Disabling a breakpoint means it cannot ' - 'cause\n' - ' the program to stop execution, but unlike clearing a ' - 'breakpoint, it\n' - ' remains in the list of breakpoints and can be (re-)enabled.\n' - '\n' - 'enable bpnumber [bpnumber ...]\n' - '\n' - ' Enable the breakpoints specified.\n' - '\n' - 'ignore bpnumber [count]\n' - '\n' - ' Set the ignore count for the given breakpoint number. If ' - '*count*\n' - ' is omitted, the ignore count is set to 0. A breakpoint ' - 'becomes\n' - ' active when the ignore count is zero. When non-zero, the ' - '*count*\n' - ' is decremented each time the breakpoint is reached and the\n' - ' breakpoint is not disabled and any associated condition ' - 'evaluates\n' - ' to true.\n' - '\n' - 'condition bpnumber [condition]\n' - '\n' - ' Set a new *condition* for the breakpoint, an expression which ' - 'must\n' - ' evaluate to true before the breakpoint is honored. If ' - '*condition*\n' - ' is absent, any existing condition is removed; i.e., the ' - 'breakpoint\n' - ' is made unconditional.\n' - '\n' - 'commands [bpnumber]\n' - '\n' - ' Specify a list of commands for breakpoint number *bpnumber*. ' - 'The\n' - ' commands themselves appear on the following lines. Type a ' - 'line\n' - ' containing just "end" to terminate the commands. An example:\n' - '\n' - ' (Pdb) commands 1\n' - ' (com) p some_variable\n' - ' (com) end\n' - ' (Pdb)\n' - '\n' - ' To remove all commands from a breakpoint, type "commands" ' - 'and\n' - ' follow it immediately with "end"; that is, give no commands.\n' - '\n' - ' With no *bpnumber* argument, "commands" refers to the last\n' - ' breakpoint set.\n' - '\n' - ' You can use breakpoint commands to start your program up ' - 'again.\n' - ' Simply use the "continue" command, or "step", or any other ' - 'command\n' - ' that resumes execution.\n' - '\n' - ' Specifying any command resuming execution (currently ' - '"continue",\n' - ' "step", "next", "return", "until", "jump", "quit" and their\n' - ' abbreviations) terminates the command list (as if that ' - 'command was\n' - ' immediately followed by end). This is because any time you ' - 'resume\n' - ' execution (even with a simple next or step), you may ' - 'encounter\n' - ' another breakpoint—which could have its own command list, ' - 'leading\n' - ' to ambiguities about which list to execute.\n' - '\n' - ' If the list of commands contains the "silent" command, or a ' - 'command\n' - ' that resumes execution, then the breakpoint message ' - 'containing\n' - ' information about the frame is not displayed.\n' - '\n' - ' Changed in version 3.14: Frame information will not be ' - 'displayed if\n' - ' a command that resumes execution is present in the command ' - 'list.\n' - '\n' - 's(tep)\n' - '\n' - ' Execute the current line, stop at the first possible ' - 'occasion\n' - ' (either in a function that is called or on the next line in ' - 'the\n' - ' current function).\n' - '\n' - 'n(ext)\n' - '\n' - ' Continue execution until the next line in the current ' - 'function is\n' - ' reached or it returns. (The difference between "next" and ' - '"step"\n' - ' is that "step" stops inside a called function, while "next"\n' - ' executes called functions at (nearly) full speed, only ' - 'stopping at\n' - ' the next line in the current function.)\n' - '\n' - 'unt(il) [lineno]\n' - '\n' - ' Without argument, continue execution until the line with a ' - 'number\n' - ' greater than the current one is reached.\n' - '\n' - ' With *lineno*, continue execution until a line with a number\n' - ' greater or equal to *lineno* is reached. In both cases, also ' - 'stop\n' - ' when the current frame returns.\n' - '\n' - ' Changed in version 3.2: Allow giving an explicit line ' - 'number.\n' - '\n' - 'r(eturn)\n' - '\n' - ' Continue execution until the current function returns.\n' - '\n' - 'c(ont(inue))\n' - '\n' - ' Continue execution, only stop when a breakpoint is ' - 'encountered.\n' - '\n' - 'j(ump) lineno\n' - '\n' - ' Set the next line that will be executed. Only available in ' - 'the\n' - ' bottom-most frame. This lets you jump back and execute code ' - 'again,\n' - ' or jump forward to skip code that you don’t want to run.\n' - '\n' - ' It should be noted that not all jumps are allowed – for ' - 'instance it\n' - ' is not possible to jump into the middle of a "for" loop or ' - 'out of a\n' - ' "finally" clause.\n' - '\n' - 'l(ist) [first[, last]]\n' - '\n' - ' List source code for the current file. Without arguments, ' - 'list 11\n' - ' lines around the current line or continue the previous ' - 'listing.\n' - ' With "." as argument, list 11 lines around the current line. ' - 'With\n' - ' one argument, list 11 lines around at that line. With two\n' - ' arguments, list the given range; if the second argument is ' - 'less\n' - ' than the first, it is interpreted as a count.\n' - '\n' - ' The current line in the current frame is indicated by "->". ' - 'If an\n' - ' exception is being debugged, the line where the exception ' - 'was\n' - ' originally raised or propagated is indicated by ">>", if it ' - 'differs\n' - ' from the current line.\n' - '\n' - ' Changed in version 3.2: Added the ">>" marker.\n' - '\n' - 'll | longlist\n' - '\n' - ' List all source code for the current function or frame.\n' - ' Interesting lines are marked as for "list".\n' - '\n' - ' Added in version 3.2.\n' - '\n' - 'a(rgs)\n' - '\n' - ' Print the arguments of the current function and their ' - 'current\n' - ' values.\n' - '\n' - 'p expression\n' - '\n' - ' Evaluate *expression* in the current context and print its ' - 'value.\n' - '\n' - ' Note:\n' - '\n' - ' "print()" can also be used, but is not a debugger command — ' - 'this\n' - ' executes the Python "print()" function.\n' - '\n' - 'pp expression\n' - '\n' - ' Like the "p" command, except the value of *expression* is ' - 'pretty-\n' - ' printed using the "pprint" module.\n' - '\n' - 'whatis expression\n' - '\n' - ' Print the type of *expression*.\n' - '\n' - 'source expression\n' - '\n' - ' Try to get source code of *expression* and display it.\n' - '\n' - ' Added in version 3.2.\n' - '\n' - 'display [expression]\n' - '\n' - ' Display the value of *expression* if it changed, each time\n' - ' execution stops in the current frame.\n' - '\n' - ' Without *expression*, list all display expressions for the ' - 'current\n' - ' frame.\n' - '\n' - ' Note:\n' - '\n' - ' Display evaluates *expression* and compares to the result ' - 'of the\n' - ' previous evaluation of *expression*, so when the result is\n' - ' mutable, display may not be able to pick up the changes.\n' - '\n' - ' Example:\n' - '\n' - ' lst = []\n' - ' breakpoint()\n' - ' pass\n' - ' lst.append(1)\n' - ' print(lst)\n' - '\n' - ' Display won’t realize "lst" has been changed because the ' - 'result of\n' - ' evaluation is modified in place by "lst.append(1)" before ' - 'being\n' - ' compared:\n' - '\n' - ' > example.py(3)<module>()\n' - ' -> pass\n' - ' (Pdb) display lst\n' - ' display lst: []\n' - ' (Pdb) n\n' - ' > example.py(4)<module>()\n' - ' -> lst.append(1)\n' - ' (Pdb) n\n' - ' > example.py(5)<module>()\n' - ' -> print(lst)\n' - ' (Pdb)\n' - '\n' - ' You can do some tricks with copy mechanism to make it work:\n' - '\n' - ' > example.py(3)<module>()\n' - ' -> pass\n' - ' (Pdb) display lst[:]\n' - ' display lst[:]: []\n' - ' (Pdb) n\n' - ' > example.py(4)<module>()\n' - ' -> lst.append(1)\n' - ' (Pdb) n\n' - ' > example.py(5)<module>()\n' - ' -> print(lst)\n' - ' display lst[:]: [1] [old: []]\n' - ' (Pdb)\n' - '\n' - ' Added in version 3.2.\n' - '\n' - 'undisplay [expression]\n' - '\n' - ' Do not display *expression* anymore in the current frame. ' - 'Without\n' - ' *expression*, clear all display expressions for the current ' - 'frame.\n' - '\n' - ' Added in version 3.2.\n' - '\n' - 'interact\n' - '\n' - ' Start an interactive interpreter (using the "code" module) in ' - 'a new\n' - ' global namespace initialised from the local and global ' - 'namespaces\n' - ' for the current scope. Use "exit()" or "quit()" to exit the\n' - ' interpreter and return to the debugger.\n' - '\n' - ' Note:\n' - '\n' - ' As "interact" creates a new dedicated namespace for code\n' - ' execution, assignments to variables will not affect the ' - 'original\n' - ' namespaces. However, modifications to any referenced ' - 'mutable\n' - ' objects will be reflected in the original namespaces as ' - 'usual.\n' - '\n' - ' Added in version 3.2.\n' - '\n' - ' Changed in version 3.13: "exit()" and "quit()" can be used to ' - 'exit\n' - ' the "interact" command.\n' - '\n' - ' Changed in version 3.13: "interact" directs its output to ' - 'the\n' - ' debugger’s output channel rather than "sys.stderr".\n' - '\n' - 'alias [name [command]]\n' - '\n' - ' Create an alias called *name* that executes *command*. The\n' - ' *command* must *not* be enclosed in quotes. Replaceable ' - 'parameters\n' - ' can be indicated by "%1", "%2", … and "%9", while "%*" is ' - 'replaced\n' - ' by all the parameters. If *command* is omitted, the current ' - 'alias\n' - ' for *name* is shown. If no arguments are given, all aliases ' - 'are\n' - ' listed.\n' - '\n' - ' Aliases may be nested and can contain anything that can be ' - 'legally\n' - ' typed at the pdb prompt. Note that internal pdb commands ' - '*can* be\n' - ' overridden by aliases. Such a command is then hidden until ' - 'the\n' - ' alias is removed. Aliasing is recursively applied to the ' - 'first\n' - ' word of the command line; all other words in the line are ' - 'left\n' - ' alone.\n' - '\n' - ' As an example, here are two useful aliases (especially when ' - 'placed\n' - ' in the ".pdbrc" file):\n' - '\n' - ' # Print instance variables (usage "pi classInst")\n' - ' alias pi for k in %1.__dict__.keys(): print(f"%1.{k} = ' - '{%1.__dict__[k]}")\n' - ' # Print instance variables in self\n' - ' alias ps pi self\n' - '\n' - 'unalias name\n' - '\n' - ' Delete the specified alias *name*.\n' - '\n' - '! statement\n' - '\n' - ' Execute the (one-line) *statement* in the context of the ' - 'current\n' - ' stack frame. The exclamation point can be omitted unless the ' - 'first\n' - ' word of the statement resembles a debugger command, e.g.:\n' - '\n' - ' (Pdb) ! n=42\n' - ' (Pdb)\n' - '\n' - ' To set a global variable, you can prefix the assignment ' - 'command\n' - ' with a "global" statement on the same line, e.g.:\n' - '\n' - " (Pdb) global list_options; list_options = ['-l']\n" - ' (Pdb)\n' - '\n' - 'run [args ...]\n' - 'restart [args ...]\n' - '\n' - ' Restart the debugged Python program. If *args* is supplied, ' - 'it is\n' - ' split with "shlex" and the result is used as the new ' - '"sys.argv".\n' - ' History, breakpoints, actions and debugger options are ' - 'preserved.\n' - ' "restart" is an alias for "run".\n' - '\n' - ' Changed in version 3.14: "run" and "restart" commands are ' - 'disabled\n' - ' when the debugger is invoked in "\'inline\'" mode.\n' - '\n' - 'q(uit)\n' - '\n' - ' Quit from the debugger. The program being executed is ' - 'aborted.\n' - '\n' - 'debug code\n' - '\n' - ' Enter a recursive debugger that steps through *code* (which ' - 'is an\n' - ' arbitrary expression or statement to be executed in the ' - 'current\n' - ' environment).\n' - '\n' - 'retval\n' - '\n' - ' Print the return value for the last return of the current ' - 'function.\n' - '\n' - 'exceptions [excnumber]\n' - '\n' - ' List or jump between chained exceptions.\n' - '\n' - ' When using "pdb.pm()" or "Pdb.post_mortem(...)" with a ' - 'chained\n' - ' exception instead of a traceback, it allows the user to move\n' - ' between the chained exceptions using "exceptions" command to ' - 'list\n' - ' exceptions, and "exception <number>" to switch to that ' - 'exception.\n' - '\n' - ' Example:\n' - '\n' - ' def out():\n' - ' try:\n' - ' middle()\n' - ' except Exception as e:\n' - ' raise ValueError("reraise middle() error") from e\n' - '\n' - ' def middle():\n' - ' try:\n' - ' return inner(0)\n' - ' except Exception as e:\n' - ' raise ValueError("Middle fail")\n' - '\n' - ' def inner(x):\n' - ' 1 / x\n' - '\n' - ' out()\n' - '\n' - ' calling "pdb.pm()" will allow to move between exceptions:\n' - '\n' - ' > example.py(5)out()\n' - ' -> raise ValueError("reraise middle() error") from e\n' - '\n' - ' (Pdb) exceptions\n' - " 0 ZeroDivisionError('division by zero')\n" - " 1 ValueError('Middle fail')\n" - " > 2 ValueError('reraise middle() error')\n" - '\n' - ' (Pdb) exceptions 0\n' - ' > example.py(16)inner()\n' - ' -> 1 / x\n' - '\n' - ' (Pdb) up\n' - ' > example.py(10)middle()\n' - ' -> return inner(0)\n' - '\n' - ' Added in version 3.13.\n' - '\n' - '-[ Footnotes ]-\n' - '\n' - '[1] Whether a frame is considered to originate in a certain ' - 'module is\n' - ' determined by the "__name__" in the frame globals.\n', - 'del': 'The "del" statement\n' - '*******************\n' - '\n' - ' del_stmt ::= "del" target_list\n' - '\n' - 'Deletion is recursively defined very similar to the way assignment ' - 'is\n' - 'defined. Rather than spelling it out in full details, here are some\n' - 'hints.\n' - '\n' - 'Deletion of a target list recursively deletes each target, from left\n' - 'to right.\n' - '\n' - 'Deletion of a name removes the binding of that name from the local ' - 'or\n' - 'global namespace, depending on whether the name occurs in a "global"\n' - 'statement in the same code block. If the name is unbound, a\n' - '"NameError" exception will be raised.\n' - '\n' - 'Deletion of attribute references, subscriptions and slicings is ' - 'passed\n' - 'to the primary object involved; deletion of a slicing is in general\n' - 'equivalent to assignment of an empty slice of the right type (but ' - 'even\n' - 'this is determined by the sliced object).\n' - '\n' - 'Changed in version 3.2: Previously it was illegal to delete a name\n' - 'from the local namespace if it occurs as a free variable in a nested\n' - 'block.\n', - 'dict': 'Dictionary displays\n' - '*******************\n' - '\n' - 'A dictionary display is a possibly empty series of dict items\n' - '(key/value pairs) enclosed in curly braces:\n' - '\n' - ' dict_display ::= "{" [dict_item_list | dict_comprehension] ' - '"}"\n' - ' dict_item_list ::= dict_item ("," dict_item)* [","]\n' - ' dict_item ::= expression ":" expression | "**" or_expr\n' - ' dict_comprehension ::= expression ":" expression comp_for\n' - '\n' - 'A dictionary display yields a new dictionary object.\n' - '\n' - 'If a comma-separated sequence of dict items is given, they are\n' - 'evaluated from left to right to define the entries of the ' - 'dictionary:\n' - 'each key object is used as a key into the dictionary to store the\n' - 'corresponding value. This means that you can specify the same key\n' - 'multiple times in the dict item list, and the final dictionary’s ' - 'value\n' - 'for that key will be the last one given.\n' - '\n' - 'A double asterisk "**" denotes *dictionary unpacking*. Its operand\n' - 'must be a *mapping*. Each mapping item is added to the new\n' - 'dictionary. Later values replace values already set by earlier ' - 'dict\n' - 'items and earlier dictionary unpackings.\n' - '\n' - 'Added in version 3.5: Unpacking into dictionary displays, ' - 'originally\n' - 'proposed by **PEP 448**.\n' - '\n' - 'A dict comprehension, in contrast to list and set comprehensions,\n' - 'needs two expressions separated with a colon followed by the usual\n' - '“for” and “if” clauses. When the comprehension is run, the ' - 'resulting\n' - 'key and value elements are inserted in the new dictionary in the ' - 'order\n' - 'they are produced.\n' - '\n' - 'Restrictions on the types of the key values are listed earlier in\n' - 'section The standard type hierarchy. (To summarize, the key type\n' - 'should be *hashable*, which excludes all mutable objects.) Clashes\n' - 'between duplicate keys are not detected; the last value (textually\n' - 'rightmost in the display) stored for a given key value prevails.\n' - '\n' - 'Changed in version 3.8: Prior to Python 3.8, in dict ' - 'comprehensions,\n' - 'the evaluation order of key and value was not well-defined. In\n' - 'CPython, the value was evaluated before the key. Starting with ' - '3.8,\n' - 'the key is evaluated before the value, as proposed by **PEP 572**.\n', - 'dynamic-features': 'Interaction with dynamic features\n' - '*********************************\n' - '\n' - 'Name resolution of free variables occurs at runtime, not ' - 'at compile\n' - 'time. This means that the following code will print 42:\n' - '\n' - ' i = 10\n' - ' def f():\n' - ' print(i)\n' - ' i = 42\n' - ' f()\n' - '\n' - 'The "eval()" and "exec()" functions do not have access ' - 'to the full\n' - 'environment for resolving names. Names may be resolved ' - 'in the local\n' - 'and global namespaces of the caller. Free variables are ' - 'not resolved\n' - 'in the nearest enclosing namespace, but in the global ' - 'namespace. [1]\n' - 'The "exec()" and "eval()" functions have optional ' - 'arguments to\n' - 'override the global and local namespace. If only one ' - 'namespace is\n' - 'specified, it is used for both.\n', - 'else': 'The "if" statement\n' - '******************\n' - '\n' - 'The "if" statement is used for conditional execution:\n' - '\n' - ' if_stmt ::= "if" assignment_expression ":" suite\n' - ' ("elif" assignment_expression ":" suite)*\n' - ' ["else" ":" suite]\n' - '\n' - 'It selects exactly one of the suites by evaluating the expressions ' - 'one\n' - 'by one until one is found to be true (see section Boolean ' - 'operations\n' - 'for the definition of true and false); then that suite is executed\n' - '(and no other part of the "if" statement is executed or evaluated).\n' - 'If all expressions are false, the suite of the "else" clause, if\n' - 'present, is executed.\n', - 'exceptions': 'Exceptions\n' - '**********\n' - '\n' - 'Exceptions are a means of breaking out of the normal flow of ' - 'control\n' - 'of a code block in order to handle errors or other ' - 'exceptional\n' - 'conditions. An exception is *raised* at the point where the ' - 'error is\n' - 'detected; it may be *handled* by the surrounding code block or ' - 'by any\n' - 'code block that directly or indirectly invoked the code block ' - 'where\n' - 'the error occurred.\n' - '\n' - 'The Python interpreter raises an exception when it detects a ' - 'run-time\n' - 'error (such as division by zero). A Python program can also\n' - 'explicitly raise an exception with the "raise" statement. ' - 'Exception\n' - 'handlers are specified with the "try" … "except" statement. ' - 'The\n' - '"finally" clause of such a statement can be used to specify ' - 'cleanup\n' - 'code which does not handle the exception, but is executed ' - 'whether an\n' - 'exception occurred or not in the preceding code.\n' - '\n' - 'Python uses the “termination” model of error handling: an ' - 'exception\n' - 'handler can find out what happened and continue execution at ' - 'an outer\n' - 'level, but it cannot repair the cause of the error and retry ' - 'the\n' - 'failing operation (except by re-entering the offending piece ' - 'of code\n' - 'from the top).\n' - '\n' - 'When an exception is not handled at all, the interpreter ' - 'terminates\n' - 'execution of the program, or returns to its interactive main ' - 'loop. In\n' - 'either case, it prints a stack traceback, except when the ' - 'exception is\n' - '"SystemExit".\n' - '\n' - 'Exceptions are identified by class instances. The "except" ' - 'clause is\n' - 'selected depending on the class of the instance: it must ' - 'reference the\n' - 'class of the instance or a *non-virtual base class* thereof. ' - 'The\n' - 'instance can be received by the handler and can carry ' - 'additional\n' - 'information about the exceptional condition.\n' - '\n' - 'Note:\n' - '\n' - ' Exception messages are not part of the Python API. Their ' - 'contents\n' - ' may change from one version of Python to the next without ' - 'warning\n' - ' and should not be relied on by code which will run under ' - 'multiple\n' - ' versions of the interpreter.\n' - '\n' - 'See also the description of the "try" statement in section The ' - 'try\n' - 'statement and "raise" statement in section The raise ' - 'statement.\n' - '\n' - '-[ Footnotes ]-\n' - '\n' - '[1] This limitation occurs because the code that is executed ' - 'by these\n' - ' operations is not available at the time the module is ' - 'compiled.\n', - 'execmodel': 'Execution model\n' - '***************\n' - '\n' - '\n' - 'Structure of a program\n' - '======================\n' - '\n' - 'A Python program is constructed from code blocks. A *block* is ' - 'a piece\n' - 'of Python program text that is executed as a unit. The ' - 'following are\n' - 'blocks: a module, a function body, and a class definition. ' - 'Each\n' - 'command typed interactively is a block. A script file (a file ' - 'given\n' - 'as standard input to the interpreter or specified as a command ' - 'line\n' - 'argument to the interpreter) is a code block. A script command ' - '(a\n' - 'command specified on the interpreter command line with the ' - '"-c"\n' - 'option) is a code block. A module run as a top level script (as ' - 'module\n' - '"__main__") from the command line using a "-m" argument is also ' - 'a code\n' - 'block. The string argument passed to the built-in functions ' - '"eval()"\n' - 'and "exec()" is a code block.\n' - '\n' - 'A code block is executed in an *execution frame*. A frame ' - 'contains\n' - 'some administrative information (used for debugging) and ' - 'determines\n' - 'where and how execution continues after the code block’s ' - 'execution has\n' - 'completed.\n' - '\n' - '\n' - 'Naming and binding\n' - '==================\n' - '\n' - '\n' - 'Binding of names\n' - '----------------\n' - '\n' - '*Names* refer to objects. Names are introduced by name ' - 'binding\n' - 'operations.\n' - '\n' - 'The following constructs bind names:\n' - '\n' - '* formal parameters to functions,\n' - '\n' - '* class definitions,\n' - '\n' - '* function definitions,\n' - '\n' - '* assignment expressions,\n' - '\n' - '* targets that are identifiers if occurring in an assignment:\n' - '\n' - ' * "for" loop header,\n' - '\n' - ' * after "as" in a "with" statement, "except" clause, ' - '"except*"\n' - ' clause, or in the as-pattern in structural pattern ' - 'matching,\n' - '\n' - ' * in a capture pattern in structural pattern matching\n' - '\n' - '* "import" statements.\n' - '\n' - '* "type" statements.\n' - '\n' - '* type parameter lists.\n' - '\n' - 'The "import" statement of the form "from ... import *" binds ' - 'all names\n' - 'defined in the imported module, except those beginning with an\n' - 'underscore. This form may only be used at the module level.\n' - '\n' - 'A target occurring in a "del" statement is also considered ' - 'bound for\n' - 'this purpose (though the actual semantics are to unbind the ' - 'name).\n' - '\n' - 'Each assignment or import statement occurs within a block ' - 'defined by a\n' - 'class or function definition or at the module level (the ' - 'top-level\n' - 'code block).\n' - '\n' - 'If a name is bound in a block, it is a local variable of that ' - 'block,\n' - 'unless declared as "nonlocal" or "global". If a name is bound ' - 'at the\n' - 'module level, it is a global variable. (The variables of the ' - 'module\n' - 'code block are local and global.) If a variable is used in a ' - 'code\n' - 'block but not defined there, it is a *free variable*.\n' - '\n' - 'Each occurrence of a name in the program text refers to the ' - '*binding*\n' - 'of that name established by the following name resolution ' - 'rules.\n' - '\n' - '\n' - 'Resolution of names\n' - '-------------------\n' - '\n' - 'A *scope* defines the visibility of a name within a block. If ' - 'a local\n' - 'variable is defined in a block, its scope includes that block. ' - 'If the\n' - 'definition occurs in a function block, the scope extends to any ' - 'blocks\n' - 'contained within the defining one, unless a contained block ' - 'introduces\n' - 'a different binding for the name.\n' - '\n' - 'When a name is used in a code block, it is resolved using the ' - 'nearest\n' - 'enclosing scope. The set of all such scopes visible to a code ' - 'block\n' - 'is called the block’s *environment*.\n' - '\n' - 'When a name is not found at all, a "NameError" exception is ' - 'raised. If\n' - 'the current scope is a function scope, and the name refers to a ' - 'local\n' - 'variable that has not yet been bound to a value at the point ' - 'where the\n' - 'name is used, an "UnboundLocalError" exception is raised.\n' - '"UnboundLocalError" is a subclass of "NameError".\n' - '\n' - 'If a name binding operation occurs anywhere within a code ' - 'block, all\n' - 'uses of the name within the block are treated as references to ' - 'the\n' - 'current block. This can lead to errors when a name is used ' - 'within a\n' - 'block before it is bound. This rule is subtle. Python lacks\n' - 'declarations and allows name binding operations to occur ' - 'anywhere\n' - 'within a code block. The local variables of a code block can ' - 'be\n' - 'determined by scanning the entire text of the block for name ' - 'binding\n' - 'operations. See the FAQ entry on UnboundLocalError for ' - 'examples.\n' - '\n' - 'If the "global" statement occurs within a block, all uses of ' - 'the names\n' - 'specified in the statement refer to the bindings of those names ' - 'in the\n' - 'top-level namespace. Names are resolved in the top-level ' - 'namespace by\n' - 'searching the global namespace, i.e. the namespace of the ' - 'module\n' - 'containing the code block, and the builtins namespace, the ' - 'namespace\n' - 'of the module "builtins". The global namespace is searched ' - 'first. If\n' - 'the names are not found there, the builtins namespace is ' - 'searched\n' - 'next. If the names are also not found in the builtins ' - 'namespace, new\n' - 'variables are created in the global namespace. The global ' - 'statement\n' - 'must precede all uses of the listed names.\n' - '\n' - 'The "global" statement has the same scope as a name binding ' - 'operation\n' - 'in the same block. If the nearest enclosing scope for a free ' - 'variable\n' - 'contains a global statement, the free variable is treated as a ' - 'global.\n' - '\n' - 'The "nonlocal" statement causes corresponding names to refer ' - 'to\n' - 'previously bound variables in the nearest enclosing function ' - 'scope.\n' - '"SyntaxError" is raised at compile time if the given name does ' - 'not\n' - 'exist in any enclosing function scope. Type parameters cannot ' - 'be\n' - 'rebound with the "nonlocal" statement.\n' - '\n' - 'The namespace for a module is automatically created the first ' - 'time a\n' - 'module is imported. The main module for a script is always ' - 'called\n' - '"__main__".\n' - '\n' - 'Class definition blocks and arguments to "exec()" and "eval()" ' - 'are\n' - 'special in the context of name resolution. A class definition ' - 'is an\n' - 'executable statement that may use and define names. These ' - 'references\n' - 'follow the normal rules for name resolution with an exception ' - 'that\n' - 'unbound local variables are looked up in the global namespace. ' - 'The\n' - 'namespace of the class definition becomes the attribute ' - 'dictionary of\n' - 'the class. The scope of names defined in a class block is ' - 'limited to\n' - 'the class block; it does not extend to the code blocks of ' - 'methods.\n' - 'This includes comprehensions and generator expressions, but it ' - 'does\n' - 'not include annotation scopes, which have access to their ' - 'enclosing\n' - 'class scopes. This means that the following will fail:\n' - '\n' - ' class A:\n' - ' a = 42\n' - ' b = list(a + i for i in range(10))\n' - '\n' - 'However, the following will succeed:\n' - '\n' - ' class A:\n' - ' type Alias = Nested\n' - ' class Nested: pass\n' - '\n' - " print(A.Alias.__value__) # <type 'A.Nested'>\n" - '\n' - '\n' - 'Annotation scopes\n' - '-----------------\n' - '\n' - '*Annotations*, type parameter lists and "type" statements ' - 'introduce\n' - '*annotation scopes*, which behave mostly like function scopes, ' - 'but\n' - 'with some exceptions discussed below.\n' - '\n' - 'Annotation scopes are used in the following contexts:\n' - '\n' - '* *Function annotations*.\n' - '\n' - '* *Variable annotations*.\n' - '\n' - '* Type parameter lists for generic type aliases.\n' - '\n' - '* Type parameter lists for generic functions. A generic ' - 'function’s\n' - ' annotations are executed within the annotation scope, but ' - 'its\n' - ' defaults and decorators are not.\n' - '\n' - '* Type parameter lists for generic classes. A generic class’s ' - 'base\n' - ' classes and keyword arguments are executed within the ' - 'annotation\n' - ' scope, but its decorators are not.\n' - '\n' - '* The bounds, constraints, and default values for type ' - 'parameters\n' - ' (lazily evaluated).\n' - '\n' - '* The value of type aliases (lazily evaluated).\n' - '\n' - 'Annotation scopes differ from function scopes in the following ' - 'ways:\n' - '\n' - '* Annotation scopes have access to their enclosing class ' - 'namespace. If\n' - ' an annotation scope is immediately within a class scope, or ' - 'within\n' - ' another annotation scope that is immediately within a class ' - 'scope,\n' - ' the code in the annotation scope can use names defined in the ' - 'class\n' - ' scope as if it were executed directly within the class body. ' - 'This\n' - ' contrasts with regular functions defined within classes, ' - 'which\n' - ' cannot access names defined in the class scope.\n' - '\n' - '* Expressions in annotation scopes cannot contain "yield", ' - '"yield\n' - ' from", "await", or ":=" expressions. (These expressions are ' - 'allowed\n' - ' in other scopes contained within the annotation scope.)\n' - '\n' - '* Names defined in annotation scopes cannot be rebound with ' - '"nonlocal"\n' - ' statements in inner scopes. This includes only type ' - 'parameters, as\n' - ' no other syntactic elements that can appear within annotation ' - 'scopes\n' - ' can introduce new names.\n' - '\n' - '* While annotation scopes have an internal name, that name is ' - 'not\n' - ' reflected in the *qualified name* of objects defined within ' - 'the\n' - ' scope. Instead, the "__qualname__" of such objects is as if ' - 'the\n' - ' object were defined in the enclosing scope.\n' - '\n' - 'Added in version 3.12: Annotation scopes were introduced in ' - 'Python\n' - '3.12 as part of **PEP 695**.\n' - '\n' - 'Changed in version 3.13: Annotation scopes are also used for ' - 'type\n' - 'parameter defaults, as introduced by **PEP 696**.\n' - '\n' - 'Changed in version 3.14: Annotation scopes are now also used ' - 'for\n' - 'annotations, as specified in **PEP 649** and **PEP 749**.\n' - '\n' - '\n' - 'Lazy evaluation\n' - '---------------\n' - '\n' - 'Most annotation scopes are *lazily evaluated*. This includes\n' - 'annotations, the values of type aliases created through the ' - '"type"\n' - 'statement, and the bounds, constraints, and default values of ' - 'type\n' - 'variables created through the type parameter syntax. This means ' - 'that\n' - 'they are not evaluated when the type alias or type variable is\n' - 'created, or when the object carrying annotations is created. ' - 'Instead,\n' - 'they are only evaluated when necessary, for example when the\n' - '"__value__" attribute on a type alias is accessed.\n' - '\n' - 'Example:\n' - '\n' - ' >>> type Alias = 1/0\n' - ' >>> Alias.__value__\n' - ' Traceback (most recent call last):\n' - ' ...\n' - ' ZeroDivisionError: division by zero\n' - ' >>> def func[T: 1/0](): pass\n' - ' >>> T = func.__type_params__[0]\n' - ' >>> T.__bound__\n' - ' Traceback (most recent call last):\n' - ' ...\n' - ' ZeroDivisionError: division by zero\n' - '\n' - 'Here the exception is raised only when the "__value__" ' - 'attribute of\n' - 'the type alias or the "__bound__" attribute of the type ' - 'variable is\n' - 'accessed.\n' - '\n' - 'This behavior is primarily useful for references to types that ' - 'have\n' - 'not yet been defined when the type alias or type variable is ' - 'created.\n' - 'For example, lazy evaluation enables creation of mutually ' - 'recursive\n' - 'type aliases:\n' - '\n' - ' from typing import Literal\n' - '\n' - ' type SimpleExpr = int | Parenthesized\n' - ' type Parenthesized = tuple[Literal["("], Expr, ' - 'Literal[")"]]\n' - ' type Expr = SimpleExpr | tuple[SimpleExpr, Literal["+", ' - '"-"], Expr]\n' - '\n' - 'Lazily evaluated values are evaluated in annotation scope, ' - 'which means\n' - 'that names that appear inside the lazily evaluated value are ' - 'looked up\n' - 'as if they were used in the immediately enclosing scope.\n' - '\n' - 'Added in version 3.12.\n' - '\n' - '\n' - 'Builtins and restricted execution\n' - '---------------------------------\n' - '\n' - '**CPython implementation detail:** Users should not touch\n' - '"__builtins__"; it is strictly an implementation detail. ' - 'Users\n' - 'wanting to override values in the builtins namespace should ' - '"import"\n' - 'the "builtins" module and modify its attributes appropriately.\n' - '\n' - 'The builtins namespace associated with the execution of a code ' - 'block\n' - 'is actually found by looking up the name "__builtins__" in its ' - 'global\n' - 'namespace; this should be a dictionary or a module (in the ' - 'latter case\n' - 'the module’s dictionary is used). By default, when in the ' - '"__main__"\n' - 'module, "__builtins__" is the built-in module "builtins"; when ' - 'in any\n' - 'other module, "__builtins__" is an alias for the dictionary of ' - 'the\n' - '"builtins" module itself.\n' - '\n' - '\n' - 'Interaction with dynamic features\n' - '---------------------------------\n' - '\n' - 'Name resolution of free variables occurs at runtime, not at ' - 'compile\n' - 'time. This means that the following code will print 42:\n' - '\n' - ' i = 10\n' - ' def f():\n' - ' print(i)\n' - ' i = 42\n' - ' f()\n' - '\n' - 'The "eval()" and "exec()" functions do not have access to the ' - 'full\n' - 'environment for resolving names. Names may be resolved in the ' - 'local\n' - 'and global namespaces of the caller. Free variables are not ' - 'resolved\n' - 'in the nearest enclosing namespace, but in the global ' - 'namespace. [1]\n' - 'The "exec()" and "eval()" functions have optional arguments to\n' - 'override the global and local namespace. If only one namespace ' - 'is\n' - 'specified, it is used for both.\n' - '\n' - '\n' - 'Exceptions\n' - '==========\n' - '\n' - 'Exceptions are a means of breaking out of the normal flow of ' - 'control\n' - 'of a code block in order to handle errors or other exceptional\n' - 'conditions. An exception is *raised* at the point where the ' - 'error is\n' - 'detected; it may be *handled* by the surrounding code block or ' - 'by any\n' - 'code block that directly or indirectly invoked the code block ' - 'where\n' - 'the error occurred.\n' - '\n' - 'The Python interpreter raises an exception when it detects a ' - 'run-time\n' - 'error (such as division by zero). A Python program can also\n' - 'explicitly raise an exception with the "raise" statement. ' - 'Exception\n' - 'handlers are specified with the "try" … "except" statement. ' - 'The\n' - '"finally" clause of such a statement can be used to specify ' - 'cleanup\n' - 'code which does not handle the exception, but is executed ' - 'whether an\n' - 'exception occurred or not in the preceding code.\n' - '\n' - 'Python uses the “termination” model of error handling: an ' - 'exception\n' - 'handler can find out what happened and continue execution at an ' - 'outer\n' - 'level, but it cannot repair the cause of the error and retry ' - 'the\n' - 'failing operation (except by re-entering the offending piece of ' - 'code\n' - 'from the top).\n' - '\n' - 'When an exception is not handled at all, the interpreter ' - 'terminates\n' - 'execution of the program, or returns to its interactive main ' - 'loop. In\n' - 'either case, it prints a stack traceback, except when the ' - 'exception is\n' - '"SystemExit".\n' - '\n' - 'Exceptions are identified by class instances. The "except" ' - 'clause is\n' - 'selected depending on the class of the instance: it must ' - 'reference the\n' - 'class of the instance or a *non-virtual base class* thereof. ' - 'The\n' - 'instance can be received by the handler and can carry ' - 'additional\n' - 'information about the exceptional condition.\n' - '\n' - 'Note:\n' - '\n' - ' Exception messages are not part of the Python API. Their ' - 'contents\n' - ' may change from one version of Python to the next without ' - 'warning\n' - ' and should not be relied on by code which will run under ' - 'multiple\n' - ' versions of the interpreter.\n' - '\n' - 'See also the description of the "try" statement in section The ' - 'try\n' - 'statement and "raise" statement in section The raise ' - 'statement.\n' - '\n' - '-[ Footnotes ]-\n' - '\n' - '[1] This limitation occurs because the code that is executed by ' - 'these\n' - ' operations is not available at the time the module is ' - 'compiled.\n', - 'exprlists': 'Expression lists\n' - '****************\n' - '\n' - ' starred_expression ::= ["*"] or_expr\n' - ' flexible_expression ::= assignment_expression | ' - 'starred_expression\n' - ' flexible_expression_list ::= flexible_expression ("," ' - 'flexible_expression)* [","]\n' - ' starred_expression_list ::= starred_expression ("," ' - 'starred_expression)* [","]\n' - ' expression_list ::= expression ("," expression)* ' - '[","]\n' - ' yield_list ::= expression_list | ' - 'starred_expression "," [starred_expression_list]\n' - '\n' - 'Except when part of a list or set display, an expression list\n' - 'containing at least one comma yields a tuple. The length of ' - 'the tuple\n' - 'is the number of expressions in the list. The expressions are\n' - 'evaluated from left to right.\n' - '\n' - 'An asterisk "*" denotes *iterable unpacking*. Its operand must ' - 'be an\n' - '*iterable*. The iterable is expanded into a sequence of items, ' - 'which\n' - 'are included in the new tuple, list, or set, at the site of ' - 'the\n' - 'unpacking.\n' - '\n' - 'Added in version 3.5: Iterable unpacking in expression lists,\n' - 'originally proposed by **PEP 448**.\n' - '\n' - 'Added in version 3.11: Any item in an expression list may be ' - 'starred.\n' - 'See **PEP 646**.\n' - '\n' - 'A trailing comma is required only to create a one-item tuple, ' - 'such as\n' - '"1,"; it is optional in all other cases. A single expression ' - 'without a\n' - 'trailing comma doesn’t create a tuple, but rather yields the ' - 'value of\n' - 'that expression. (To create an empty tuple, use an empty pair ' - 'of\n' - 'parentheses: "()".)\n', - 'floating': 'Floating-point literals\n' - '***********************\n' - '\n' - 'Floating-point literals are described by the following lexical\n' - 'definitions:\n' - '\n' - ' floatnumber ::= pointfloat | exponentfloat\n' - ' pointfloat ::= [digitpart] fraction | digitpart "."\n' - ' exponentfloat ::= (digitpart | pointfloat) exponent\n' - ' digitpart ::= digit (["_"] digit)*\n' - ' fraction ::= "." digitpart\n' - ' exponent ::= ("e" | "E") ["+" | "-"] digitpart\n' - '\n' - 'Note that the integer and exponent parts are always interpreted ' - 'using\n' - 'radix 10. For example, "077e010" is legal, and denotes the same ' - 'number\n' - 'as "77e10". The allowed range of floating-point literals is\n' - 'implementation-dependent. As in integer literals, underscores ' - 'are\n' - 'supported for digit grouping.\n' - '\n' - 'Some examples of floating-point literals:\n' - '\n' - ' 3.14 10. .001 1e100 3.14e-10 0e0 ' - '3.14_15_93\n' - '\n' - 'Changed in version 3.6: Underscores are now allowed for ' - 'grouping\n' - 'purposes in literals.\n', - 'for': 'The "for" statement\n' - '*******************\n' - '\n' - 'The "for" statement is used to iterate over the elements of a ' - 'sequence\n' - '(such as a string, tuple or list) or other iterable object:\n' - '\n' - ' for_stmt ::= "for" target_list "in" starred_list ":" suite\n' - ' ["else" ":" suite]\n' - '\n' - 'The "starred_list" expression is evaluated once; it should yield an\n' - '*iterable* object. An *iterator* is created for that iterable. The\n' - 'first item provided by the iterator is then assigned to the target\n' - 'list using the standard rules for assignments (see Assignment\n' - 'statements), and the suite is executed. This repeats for each item\n' - 'provided by the iterator. When the iterator is exhausted, the suite\n' - 'in the "else" clause, if present, is executed, and the loop\n' - 'terminates.\n' - '\n' - 'A "break" statement executed in the first suite terminates the loop\n' - 'without executing the "else" clause’s suite. A "continue" statement\n' - 'executed in the first suite skips the rest of the suite and ' - 'continues\n' - 'with the next item, or with the "else" clause if there is no next\n' - 'item.\n' - '\n' - 'The for-loop makes assignments to the variables in the target list.\n' - 'This overwrites all previous assignments to those variables ' - 'including\n' - 'those made in the suite of the for-loop:\n' - '\n' - ' for i in range(10):\n' - ' print(i)\n' - ' i = 5 # this will not affect the for-loop\n' - ' # because i will be overwritten with the ' - 'next\n' - ' # index in the range\n' - '\n' - 'Names in the target list are not deleted when the loop is finished,\n' - 'but if the sequence is empty, they will not have been assigned to at\n' - 'all by the loop. Hint: the built-in type "range()" represents\n' - 'immutable arithmetic sequences of integers. For instance, iterating\n' - '"range(3)" successively yields 0, 1, and then 2.\n' - '\n' - 'Changed in version 3.11: Starred elements are now allowed in the\n' - 'expression list.\n', - 'formatstrings': 'Format String Syntax\n' - '********************\n' - '\n' - 'The "str.format()" method and the "Formatter" class share ' - 'the same\n' - 'syntax for format strings (although in the case of ' - '"Formatter",\n' - 'subclasses can define their own format string syntax). The ' - 'syntax is\n' - 'related to that of formatted string literals, but it is ' - 'less\n' - 'sophisticated and, in particular, does not support ' - 'arbitrary\n' - 'expressions.\n' - '\n' - 'Format strings contain “replacement fields” surrounded by ' - 'curly braces\n' - '"{}". Anything that is not contained in braces is ' - 'considered literal\n' - 'text, which is copied unchanged to the output. If you need ' - 'to include\n' - 'a brace character in the literal text, it can be escaped by ' - 'doubling:\n' - '"{{" and "}}".\n' - '\n' - 'The grammar for a replacement field is as follows:\n' - '\n' - ' replacement_field ::= "{" [field_name] ["!" conversion] ' - '[":" format_spec] "}"\n' - ' field_name ::= arg_name ("." attribute_name | "[" ' - 'element_index "]")*\n' - ' arg_name ::= [identifier | digit+]\n' - ' attribute_name ::= identifier\n' - ' element_index ::= digit+ | index_string\n' - ' index_string ::= <any source character except "]"> ' - '+\n' - ' conversion ::= "r" | "s" | "a"\n' - ' format_spec ::= format-spec:format_spec\n' - '\n' - 'In less formal terms, the replacement field can start with ' - 'a\n' - '*field_name* that specifies the object whose value is to be ' - 'formatted\n' - 'and inserted into the output instead of the replacement ' - 'field. The\n' - '*field_name* is optionally followed by a *conversion* ' - 'field, which is\n' - 'preceded by an exclamation point "\'!\'", and a ' - '*format_spec*, which is\n' - 'preceded by a colon "\':\'". These specify a non-default ' - 'format for the\n' - 'replacement value.\n' - '\n' - 'See also the Format Specification Mini-Language section.\n' - '\n' - 'The *field_name* itself begins with an *arg_name* that is ' - 'either a\n' - 'number or a keyword. If it’s a number, it refers to a ' - 'positional\n' - 'argument, and if it’s a keyword, it refers to a named ' - 'keyword\n' - 'argument. An *arg_name* is treated as a number if a call ' - 'to\n' - '"str.isdecimal()" on the string would return true. If the ' - 'numerical\n' - 'arg_names in a format string are 0, 1, 2, … in sequence, ' - 'they can all\n' - 'be omitted (not just some) and the numbers 0, 1, 2, … will ' - 'be\n' - 'automatically inserted in that order. Because *arg_name* is ' - 'not quote-\n' - 'delimited, it is not possible to specify arbitrary ' - 'dictionary keys\n' - '(e.g., the strings "\'10\'" or "\':-]\'") within a format ' - 'string. The\n' - '*arg_name* can be followed by any number of index or ' - 'attribute\n' - 'expressions. An expression of the form "\'.name\'" selects ' - 'the named\n' - 'attribute using "getattr()", while an expression of the ' - 'form\n' - '"\'[index]\'" does an index lookup using "__getitem__()".\n' - '\n' - 'Changed in version 3.1: The positional argument specifiers ' - 'can be\n' - 'omitted for "str.format()", so "\'{} {}\'.format(a, b)" is ' - 'equivalent to\n' - '"\'{0} {1}\'.format(a, b)".\n' - '\n' - 'Changed in version 3.4: The positional argument specifiers ' - 'can be\n' - 'omitted for "Formatter".\n' - '\n' - 'Some simple format string examples:\n' - '\n' - ' "First, thou shalt count to {0}" # References first ' - 'positional argument\n' - ' "Bring me a {}" # Implicitly ' - 'references the first positional argument\n' - ' "From {} to {}" # Same as "From {0} to ' - '{1}"\n' - ' "My quest is {name}" # References keyword ' - "argument 'name'\n" - ' "Weight in tons {0.weight}" # \'weight\' attribute ' - 'of first positional arg\n' - ' "Units destroyed: {players[0]}" # First element of ' - "keyword argument 'players'.\n" - '\n' - 'The *conversion* field causes a type coercion before ' - 'formatting.\n' - 'Normally, the job of formatting a value is done by the ' - '"__format__()"\n' - 'method of the value itself. However, in some cases it is ' - 'desirable to\n' - 'force a type to be formatted as a string, overriding its ' - 'own\n' - 'definition of formatting. By converting the value to a ' - 'string before\n' - 'calling "__format__()", the normal formatting logic is ' - 'bypassed.\n' - '\n' - 'Three conversion flags are currently supported: "\'!s\'" ' - 'which calls\n' - '"str()" on the value, "\'!r\'" which calls "repr()" and ' - '"\'!a\'" which\n' - 'calls "ascii()".\n' - '\n' - 'Some examples:\n' - '\n' - ' "Harold\'s a clever {0!s}" # Calls str() on the ' - 'argument first\n' - ' "Bring out the holy {name!r}" # Calls repr() on the ' - 'argument first\n' - ' "More {!a}" # Calls ascii() on the ' - 'argument first\n' - '\n' - 'The *format_spec* field contains a specification of how the ' - 'value\n' - 'should be presented, including such details as field width, ' - 'alignment,\n' - 'padding, decimal precision and so on. Each value type can ' - 'define its\n' - 'own “formatting mini-language” or interpretation of the ' - '*format_spec*.\n' - '\n' - 'Most built-in types support a common formatting ' - 'mini-language, which\n' - 'is described in the next section.\n' - '\n' - 'A *format_spec* field can also include nested replacement ' - 'fields\n' - 'within it. These nested replacement fields may contain a ' - 'field name,\n' - 'conversion flag and format specification, but deeper ' - 'nesting is not\n' - 'allowed. The replacement fields within the format_spec ' - 'are\n' - 'substituted before the *format_spec* string is interpreted. ' - 'This\n' - 'allows the formatting of a value to be dynamically ' - 'specified.\n' - '\n' - 'See the Format examples section for some examples.\n' - '\n' - '\n' - 'Format Specification Mini-Language\n' - '==================================\n' - '\n' - '“Format specifications” are used within replacement fields ' - 'contained\n' - 'within a format string to define how individual values are ' - 'presented\n' - '(see Format String Syntax and f-strings). They can also be ' - 'passed\n' - 'directly to the built-in "format()" function. Each ' - 'formattable type\n' - 'may define how the format specification is to be ' - 'interpreted.\n' - '\n' - 'Most built-in types implement the following options for ' - 'format\n' - 'specifications, although some of the formatting options are ' - 'only\n' - 'supported by the numeric types.\n' - '\n' - 'A general convention is that an empty format specification ' - 'produces\n' - 'the same result as if you had called "str()" on the value. ' - 'A non-empty\n' - 'format specification typically modifies the result.\n' - '\n' - 'The general form of a *standard format specifier* is:\n' - '\n' - ' format_spec ::= ' - '[[fill]align][sign]["z"]["#"]["0"][width][grouping_option]["." ' - 'precision][type]\n' - ' fill ::= <any character>\n' - ' align ::= "<" | ">" | "=" | "^"\n' - ' sign ::= "+" | "-" | " "\n' - ' width ::= digit+\n' - ' grouping_option ::= "_" | ","\n' - ' precision ::= digit+\n' - ' type ::= "b" | "c" | "d" | "e" | "E" | "f" | ' - '"F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"\n' - '\n' - 'If a valid *align* value is specified, it can be preceded ' - 'by a *fill*\n' - 'character that can be any character and defaults to a space ' - 'if\n' - 'omitted. It is not possible to use a literal curly brace ' - '(”"{"” or\n' - '“"}"”) as the *fill* character in a formatted string ' - 'literal or when\n' - 'using the "str.format()" method. However, it is possible ' - 'to insert a\n' - 'curly brace with a nested replacement field. This ' - 'limitation doesn’t\n' - 'affect the "format()" function.\n' - '\n' - 'The meaning of the various alignment options is as ' - 'follows:\n' - '\n' - '+-----------+------------------------------------------------------------+\n' - '| Option | ' - 'Meaning ' - '|\n' - '|===========|============================================================|\n' - '| "\'<\'" | Forces the field to be left-aligned within ' - 'the available |\n' - '| | space (this is the default for most ' - 'objects). |\n' - '+-----------+------------------------------------------------------------+\n' - '| "\'>\'" | Forces the field to be right-aligned within ' - 'the available |\n' - '| | space (this is the default for ' - 'numbers). |\n' - '+-----------+------------------------------------------------------------+\n' - '| "\'=\'" | Forces the padding to be placed after the ' - 'sign (if any) |\n' - '| | but before the digits. This is used for ' - 'printing fields |\n' - '| | in the form ‘+000000120’. This alignment ' - 'option is only |\n' - '| | valid for numeric types, excluding "complex". ' - 'It becomes |\n' - '| | the default for numbers when ‘0’ immediately ' - 'precedes the |\n' - '| | field ' - 'width. |\n' - '+-----------+------------------------------------------------------------+\n' - '| "\'^\'" | Forces the field to be centered within the ' - 'available |\n' - '| | ' - 'space. ' - '|\n' - '+-----------+------------------------------------------------------------+\n' - '\n' - 'Note that unless a minimum field width is defined, the ' - 'field width\n' - 'will always be the same size as the data to fill it, so ' - 'that the\n' - 'alignment option has no meaning in this case.\n' - '\n' - 'The *sign* option is only valid for number types, and can ' - 'be one of\n' - 'the following:\n' - '\n' - '+-----------+------------------------------------------------------------+\n' - '| Option | ' - 'Meaning ' - '|\n' - '|===========|============================================================|\n' - '| "\'+\'" | indicates that a sign should be used for ' - 'both positive as |\n' - '| | well as negative ' - 'numbers. |\n' - '+-----------+------------------------------------------------------------+\n' - '| "\'-\'" | indicates that a sign should be used only ' - 'for negative |\n' - '| | numbers (this is the default ' - 'behavior). |\n' - '+-----------+------------------------------------------------------------+\n' - '| space | indicates that a leading space should be used ' - 'on positive |\n' - '| | numbers, and a minus sign on negative ' - 'numbers. |\n' - '+-----------+------------------------------------------------------------+\n' - '\n' - 'The "\'z\'" option coerces negative zero floating-point ' - 'values to\n' - 'positive zero after rounding to the format precision. This ' - 'option is\n' - 'only valid for floating-point presentation types.\n' - '\n' - 'Changed in version 3.11: Added the "\'z\'" option (see also ' - '**PEP\n' - '682**).\n' - '\n' - 'The "\'#\'" option causes the “alternate form” to be used ' - 'for the\n' - 'conversion. The alternate form is defined differently for ' - 'different\n' - 'types. This option is only valid for integer, float and ' - 'complex\n' - 'types. For integers, when binary, octal, or hexadecimal ' - 'output is\n' - 'used, this option adds the respective prefix "\'0b\'", ' - '"\'0o\'", "\'0x\'",\n' - 'or "\'0X\'" to the output value. For float and complex the ' - 'alternate\n' - 'form causes the result of the conversion to always contain ' - 'a decimal-\n' - 'point character, even if no digits follow it. Normally, a ' - 'decimal-\n' - 'point character appears in the result of these conversions ' - 'only if a\n' - 'digit follows it. In addition, for "\'g\'" and "\'G\'" ' - 'conversions,\n' - 'trailing zeros are not removed from the result.\n' - '\n' - 'The "\',\'" option signals the use of a comma for a ' - 'thousands separator\n' - 'for floating-point presentation types and for integer ' - 'presentation\n' - 'type "\'d\'". For other presentation types, this option is ' - 'an error. For\n' - 'a locale aware separator, use the "\'n\'" integer ' - 'presentation type\n' - 'instead.\n' - '\n' - 'Changed in version 3.1: Added the "\',\'" option (see also ' - '**PEP 378**).\n' - '\n' - 'The "\'_\'" option signals the use of an underscore for a ' - 'thousands\n' - 'separator for floating-point presentation types and for ' - 'integer\n' - 'presentation type "\'d\'". For integer presentation types ' - '"\'b\'", "\'o\'",\n' - '"\'x\'", and "\'X\'", underscores will be inserted every 4 ' - 'digits. For\n' - 'other presentation types, specifying this option is an ' - 'error.\n' - '\n' - 'Changed in version 3.6: Added the "\'_\'" option (see also ' - '**PEP 515**).\n' - '\n' - '*width* is a decimal integer defining the minimum total ' - 'field width,\n' - 'including any prefixes, separators, and other formatting ' - 'characters.\n' - 'If not specified, then the field width will be determined ' - 'by the\n' - 'content.\n' - '\n' - 'When no explicit alignment is given, preceding the *width* ' - 'field by a\n' - 'zero ("\'0\'") character enables sign-aware zero-padding ' - 'for numeric\n' - 'types, excluding "complex". This is equivalent to a *fill* ' - 'character\n' - 'of "\'0\'" with an *alignment* type of "\'=\'".\n' - '\n' - 'Changed in version 3.10: Preceding the *width* field by ' - '"\'0\'" no\n' - 'longer affects the default alignment for strings.\n' - '\n' - 'The *precision* is a decimal integer indicating how many ' - 'digits should\n' - 'be displayed after the decimal point for presentation types ' - '"\'f\'" and\n' - '"\'F\'", or before and after the decimal point for ' - 'presentation types\n' - '"\'g\'" or "\'G\'". For string presentation types the ' - 'field indicates the\n' - 'maximum field size - in other words, how many characters ' - 'will be used\n' - 'from the field content. The *precision* is not allowed for ' - 'integer\n' - 'presentation types.\n' - '\n' - 'Finally, the *type* determines how the data should be ' - 'presented.\n' - '\n' - 'The available string presentation types are:\n' - '\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | Type | ' - 'Meaning ' - '|\n' - ' ' - '|===========|============================================================|\n' - ' | "\'s\'" | String format. This is the default type ' - 'for strings and |\n' - ' | | may be ' - 'omitted. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | None | The same as ' - '"\'s\'". |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - '\n' - 'The available integer presentation types are:\n' - '\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | Type | ' - 'Meaning ' - '|\n' - ' ' - '|===========|============================================================|\n' - ' | "\'b\'" | Binary format. Outputs the number in ' - 'base 2. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'c\'" | Character. Converts the integer to the ' - 'corresponding |\n' - ' | | unicode character before ' - 'printing. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'d\'" | Decimal Integer. Outputs the number in ' - 'base 10. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'o\'" | Octal format. Outputs the number in base ' - '8. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'x\'" | Hex format. Outputs the number in base ' - '16, using lower- |\n' - ' | | case letters for the digits above ' - '9. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'X\'" | Hex format. Outputs the number in base ' - '16, using upper- |\n' - ' | | case letters for the digits above 9. In ' - 'case "\'#\'" is |\n' - ' | | specified, the prefix "\'0x\'" will be ' - 'upper-cased to "\'0X\'" |\n' - ' | | as ' - 'well. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'n\'" | Number. This is the same as "\'d\'", ' - 'except that it uses the |\n' - ' | | current locale setting to insert the ' - 'appropriate number |\n' - ' | | separator ' - 'characters. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | None | The same as ' - '"\'d\'". |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - '\n' - 'In addition to the above presentation types, integers can ' - 'be formatted\n' - 'with the floating-point presentation types listed below ' - '(except "\'n\'"\n' - 'and "None"). When doing so, "float()" is used to convert ' - 'the integer\n' - 'to a floating-point number before formatting.\n' - '\n' - 'The available presentation types for "float" and "Decimal" ' - 'values are:\n' - '\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | Type | ' - 'Meaning ' - '|\n' - ' ' - '|===========|============================================================|\n' - ' | "\'e\'" | Scientific notation. For a given ' - 'precision "p", formats |\n' - ' | | the number in scientific notation with the ' - 'letter ‘e’ |\n' - ' | | separating the coefficient from the ' - 'exponent. The |\n' - ' | | coefficient has one digit before and "p" ' - 'digits after the |\n' - ' | | decimal point, for a total of "p + 1" ' - 'significant digits. |\n' - ' | | With no precision given, uses a precision ' - 'of "6" digits |\n' - ' | | after the decimal point for "float", and ' - 'shows all |\n' - ' | | coefficient digits for "Decimal". If ' - '"p=0", the decimal |\n' - ' | | point is omitted unless the "#" option is ' - 'used. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'E\'" | Scientific notation. Same as "\'e\'" ' - 'except it uses an upper |\n' - ' | | case ‘E’ as the separator ' - 'character. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'f\'" | Fixed-point notation. For a given ' - 'precision "p", formats |\n' - ' | | the number as a decimal number with ' - 'exactly "p" digits |\n' - ' | | following the decimal point. With no ' - 'precision given, uses |\n' - ' | | a precision of "6" digits after the ' - 'decimal point for |\n' - ' | | "float", and uses a precision large enough ' - 'to show all |\n' - ' | | coefficient digits for "Decimal". If ' - '"p=0", the decimal |\n' - ' | | point is omitted unless the "#" option is ' - 'used. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'F\'" | Fixed-point notation. Same as "\'f\'", ' - 'but converts "nan" to |\n' - ' | | "NAN" and "inf" to ' - '"INF". |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'g\'" | General format. For a given precision ' - '"p >= 1", this |\n' - ' | | rounds the number to "p" significant ' - 'digits and then |\n' - ' | | formats the result in either fixed-point ' - 'format or in |\n' - ' | | scientific notation, depending on its ' - 'magnitude. A |\n' - ' | | precision of "0" is treated as equivalent ' - 'to a precision |\n' - ' | | of "1". The precise rules are as follows: ' - 'suppose that |\n' - ' | | the result formatted with presentation ' - 'type "\'e\'" and |\n' - ' | | precision "p-1" would have exponent ' - '"exp". Then, if "m <= |\n' - ' | | exp < p", where "m" is -4 for floats and ' - '-6 for |\n' - ' | | "Decimals", the number is formatted with ' - 'presentation type |\n' - ' | | "\'f\'" and precision "p-1-exp". ' - 'Otherwise, the number is |\n' - ' | | formatted with presentation type "\'e\'" ' - 'and precision |\n' - ' | | "p-1". In both cases insignificant ' - 'trailing zeros are |\n' - ' | | removed from the significand, and the ' - 'decimal point is |\n' - ' | | also removed if there are no remaining ' - 'digits following |\n' - ' | | it, unless the "\'#\'" option is used. ' - 'With no precision |\n' - ' | | given, uses a precision of "6" significant ' - 'digits for |\n' - ' | | "float". For "Decimal", the coefficient of ' - 'the result is |\n' - ' | | formed from the coefficient digits of the ' - 'value; |\n' - ' | | scientific notation is used for values ' - 'smaller than "1e-6" |\n' - ' | | in absolute value and values where the ' - 'place value of the |\n' - ' | | least significant digit is larger than 1, ' - 'and fixed-point |\n' - ' | | notation is used otherwise. Positive and ' - 'negative |\n' - ' | | infinity, positive and negative zero, and ' - 'nans, are |\n' - ' | | formatted as "inf", "-inf", "0", "-0" and ' - '"nan" |\n' - ' | | respectively, regardless of the ' - 'precision. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'G\'" | General format. Same as "\'g\'" except ' - 'switches to "\'E\'" if |\n' - ' | | the number gets too large. The ' - 'representations of infinity |\n' - ' | | and NaN are uppercased, ' - 'too. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'n\'" | Number. This is the same as "\'g\'", ' - 'except that it uses the |\n' - ' | | current locale setting to insert the ' - 'appropriate number |\n' - ' | | separator ' - 'characters. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | "\'%\'" | Percentage. Multiplies the number by 100 ' - 'and displays in |\n' - ' | | fixed ("\'f\'") format, followed by a ' - 'percent sign. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - ' | None | For "float" this is like the "\'g\'" type, ' - 'except that when |\n' - ' | | fixed- point notation is used to format ' - 'the result, it |\n' - ' | | always includes at least one digit past ' - 'the decimal point, |\n' - ' | | and switches to the scientific notation ' - 'when "exp >= p - |\n' - ' | | 1". When the precision is not specified, ' - 'the latter will |\n' - ' | | be as large as needed to represent the ' - 'given value |\n' - ' | | faithfully. For "Decimal", this is the ' - 'same as either |\n' - ' | | "\'g\'" or "\'G\'" depending on the value ' - 'of |\n' - ' | | "context.capitals" for the current decimal ' - 'context. The |\n' - ' | | overall effect is to match the output of ' - '"str()" as |\n' - ' | | altered by the other format ' - 'modifiers. |\n' - ' ' - '+-----------+------------------------------------------------------------+\n' - '\n' - 'The result should be correctly rounded to a given precision ' - '"p" of\n' - 'digits after the decimal point. The rounding mode for ' - '"float" matches\n' - 'that of the "round()" builtin. For "Decimal", the rounding ' - 'mode of\n' - 'the current context will be used.\n' - '\n' - 'The available presentation types for "complex" are the same ' - 'as those\n' - 'for "float" ("\'%\'" is not allowed). Both the real and ' - 'imaginary\n' - 'components of a complex number are formatted as ' - 'floating-point\n' - 'numbers, according to the specified presentation type. ' - 'They are\n' - 'separated by the mandatory sign of the imaginary part, the ' - 'latter\n' - 'being terminated by a "j" suffix. If the presentation type ' - 'is\n' - 'missing, the result will match the output of "str()" ' - '(complex numbers\n' - 'with a non-zero real part are also surrounded by ' - 'parentheses),\n' - 'possibly altered by other format modifiers.\n' - '\n' - '\n' - 'Format examples\n' - '===============\n' - '\n' - 'This section contains examples of the "str.format()" syntax ' - 'and\n' - 'comparison with the old "%"-formatting.\n' - '\n' - 'In most of the cases the syntax is similar to the old ' - '"%"-formatting,\n' - 'with the addition of the "{}" and with ":" used instead of ' - '"%". For\n' - 'example, "\'%03.2f\'" can be translated to "\'{:03.2f}\'".\n' - '\n' - 'The new format syntax also supports new and different ' - 'options, shown\n' - 'in the following examples.\n' - '\n' - 'Accessing arguments by position:\n' - '\n' - " >>> '{0}, {1}, {2}'.format('a', 'b', 'c')\n" - " 'a, b, c'\n" - " >>> '{}, {}, {}'.format('a', 'b', 'c') # 3.1+ only\n" - " 'a, b, c'\n" - " >>> '{2}, {1}, {0}'.format('a', 'b', 'c')\n" - " 'c, b, a'\n" - " >>> '{2}, {1}, {0}'.format(*'abc') # unpacking " - 'argument sequence\n' - " 'c, b, a'\n" - " >>> '{0}{1}{0}'.format('abra', 'cad') # arguments' " - 'indices can be repeated\n' - " 'abracadabra'\n" - '\n' - 'Accessing arguments by name:\n' - '\n' - " >>> 'Coordinates: {latitude}, " - "{longitude}'.format(latitude='37.24N', " - "longitude='-115.81W')\n" - " 'Coordinates: 37.24N, -115.81W'\n" - " >>> coord = {'latitude': '37.24N', 'longitude': " - "'-115.81W'}\n" - " >>> 'Coordinates: {latitude}, " - "{longitude}'.format(**coord)\n" - " 'Coordinates: 37.24N, -115.81W'\n" - '\n' - 'Accessing arguments’ attributes:\n' - '\n' - ' >>> c = 3-5j\n' - " >>> ('The complex number {0} is formed from the real " - "part {0.real} '\n" - " ... 'and the imaginary part {0.imag}.').format(c)\n" - " 'The complex number (3-5j) is formed from the real part " - "3.0 and the imaginary part -5.0.'\n" - ' >>> class Point:\n' - ' ... def __init__(self, x, y):\n' - ' ... self.x, self.y = x, y\n' - ' ... def __str__(self):\n' - " ... return 'Point({self.x}, " - "{self.y})'.format(self=self)\n" - ' ...\n' - ' >>> str(Point(4, 2))\n' - " 'Point(4, 2)'\n" - '\n' - 'Accessing arguments’ items:\n' - '\n' - ' >>> coord = (3, 5)\n' - " >>> 'X: {0[0]}; Y: {0[1]}'.format(coord)\n" - " 'X: 3; Y: 5'\n" - '\n' - 'Replacing "%s" and "%r":\n' - '\n' - ' >>> "repr() shows quotes: {!r}; str() doesn\'t: ' - '{!s}".format(\'test1\', \'test2\')\n' - ' "repr() shows quotes: \'test1\'; str() doesn\'t: test2"\n' - '\n' - 'Aligning the text and specifying a width:\n' - '\n' - " >>> '{:<30}'.format('left aligned')\n" - " 'left aligned '\n" - " >>> '{:>30}'.format('right aligned')\n" - " ' right aligned'\n" - " >>> '{:^30}'.format('centered')\n" - " ' centered '\n" - " >>> '{:*^30}'.format('centered') # use '*' as a fill " - 'char\n' - " '***********centered***********'\n" - '\n' - 'Replacing "%+f", "%-f", and "% f" and specifying a sign:\n' - '\n' - " >>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it " - 'always\n' - " '+3.140000; -3.140000'\n" - " >>> '{: f}; {: f}'.format(3.14, -3.14) # show a space " - 'for positive numbers\n' - " ' 3.140000; -3.140000'\n" - " >>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the " - "minus -- same as '{:f}; {:f}'\n" - " '3.140000; -3.140000'\n" - '\n' - 'Replacing "%x" and "%o" and converting the value to ' - 'different bases:\n' - '\n' - ' >>> # format also supports binary numbers\n' - ' >>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: ' - '{0:b}".format(42)\n' - " 'int: 42; hex: 2a; oct: 52; bin: 101010'\n" - ' >>> # with 0x, 0o, or 0b as prefix:\n' - ' >>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: ' - '{0:#b}".format(42)\n' - " 'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'\n" - '\n' - 'Using the comma as a thousands separator:\n' - '\n' - " >>> '{:,}'.format(1234567890)\n" - " '1,234,567,890'\n" - '\n' - 'Expressing a percentage:\n' - '\n' - ' >>> points = 19\n' - ' >>> total = 22\n' - " >>> 'Correct answers: {:.2%}'.format(points/total)\n" - " 'Correct answers: 86.36%'\n" - '\n' - 'Using type-specific formatting:\n' - '\n' - ' >>> import datetime\n' - ' >>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)\n' - " >>> '{:%Y-%m-%d %H:%M:%S}'.format(d)\n" - " '2010-07-04 12:15:58'\n" - '\n' - 'Nesting arguments and more complex examples:\n' - '\n' - " >>> for align, text in zip('<^>', ['left', 'center', " - "'right']):\n" - " ... '{0:{fill}{align}16}'.format(text, fill=align, " - 'align=align)\n' - ' ...\n' - " 'left<<<<<<<<<<<<'\n" - " '^^^^^center^^^^^'\n" - " '>>>>>>>>>>>right'\n" - ' >>>\n' - ' >>> octets = [192, 168, 0, 1]\n' - " >>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)\n" - " 'C0A80001'\n" - ' >>> int(_, 16)\n' - ' 3232235521\n' - ' >>>\n' - ' >>> width = 5\n' - ' >>> for num in range(5,12): \n' - " ... for base in 'dXob':\n" - " ... print('{0:{width}{base}}'.format(num, " - "base=base, width=width), end=' ')\n" - ' ... print()\n' - ' ...\n' - ' 5 5 5 101\n' - ' 6 6 6 110\n' - ' 7 7 7 111\n' - ' 8 8 10 1000\n' - ' 9 9 11 1001\n' - ' 10 A 12 1010\n' - ' 11 B 13 1011\n', - 'function': 'Function definitions\n' - '********************\n' - '\n' - 'A function definition defines a user-defined function object ' - '(see\n' - 'section The standard type hierarchy):\n' - '\n' - ' funcdef ::= [decorators] "def" funcname ' - '[type_params] "(" [parameter_list] ")"\n' - ' ["->" expression] ":" suite\n' - ' decorators ::= decorator+\n' - ' decorator ::= "@" assignment_expression ' - 'NEWLINE\n' - ' parameter_list ::= defparameter ("," ' - 'defparameter)* "," "/" ["," [parameter_list_no_posonly]]\n' - ' | parameter_list_no_posonly\n' - ' parameter_list_no_posonly ::= defparameter ("," ' - 'defparameter)* ["," [parameter_list_starargs]]\n' - ' | parameter_list_starargs\n' - ' parameter_list_starargs ::= "*" [star_parameter] ("," ' - 'defparameter)* ["," ["**" parameter [","]]]\n' - ' | "**" parameter [","]\n' - ' parameter ::= identifier [":" expression]\n' - ' star_parameter ::= identifier [":" ["*"] ' - 'expression]\n' - ' defparameter ::= parameter ["=" expression]\n' - ' funcname ::= identifier\n' - '\n' - 'A function definition is an executable statement. Its execution ' - 'binds\n' - 'the function name in the current local namespace to a function ' - 'object\n' - '(a wrapper around the executable code for the function). This\n' - 'function object contains a reference to the current global ' - 'namespace\n' - 'as the global namespace to be used when the function is called.\n' - '\n' - 'The function definition does not execute the function body; this ' - 'gets\n' - 'executed only when the function is called. [4]\n' - '\n' - 'A function definition may be wrapped by one or more *decorator*\n' - 'expressions. Decorator expressions are evaluated when the ' - 'function is\n' - 'defined, in the scope that contains the function definition. ' - 'The\n' - 'result must be a callable, which is invoked with the function ' - 'object\n' - 'as the only argument. The returned value is bound to the ' - 'function name\n' - 'instead of the function object. Multiple decorators are applied ' - 'in\n' - 'nested fashion. For example, the following code\n' - '\n' - ' @f1(arg)\n' - ' @f2\n' - ' def func(): pass\n' - '\n' - 'is roughly equivalent to\n' - '\n' - ' def func(): pass\n' - ' func = f1(arg)(f2(func))\n' - '\n' - 'except that the original function is not temporarily bound to ' - 'the name\n' - '"func".\n' - '\n' - 'Changed in version 3.9: Functions may be decorated with any ' - 'valid\n' - '"assignment_expression". Previously, the grammar was much more\n' - 'restrictive; see **PEP 614** for details.\n' - '\n' - 'A list of type parameters may be given in square brackets ' - 'between the\n' - 'function’s name and the opening parenthesis for its parameter ' - 'list.\n' - 'This indicates to static type checkers that the function is ' - 'generic.\n' - 'At runtime, the type parameters can be retrieved from the ' - 'function’s\n' - '"__type_params__" attribute. See Generic functions for more.\n' - '\n' - 'Changed in version 3.12: Type parameter lists are new in Python ' - '3.12.\n' - '\n' - 'When one or more *parameters* have the form *parameter* "="\n' - '*expression*, the function is said to have “default parameter ' - 'values.”\n' - 'For a parameter with a default value, the corresponding ' - '*argument* may\n' - 'be omitted from a call, in which case the parameter’s default ' - 'value is\n' - 'substituted. If a parameter has a default value, all following\n' - 'parameters up until the “"*"” must also have a default value — ' - 'this is\n' - 'a syntactic restriction that is not expressed by the grammar.\n' - '\n' - '**Default parameter values are evaluated from left to right when ' - 'the\n' - 'function definition is executed.** This means that the ' - 'expression is\n' - 'evaluated once, when the function is defined, and that the same ' - '“pre-\n' - 'computed” value is used for each call. This is especially ' - 'important\n' - 'to understand when a default parameter value is a mutable ' - 'object, such\n' - 'as a list or a dictionary: if the function modifies the object ' - '(e.g.\n' - 'by appending an item to a list), the default parameter value is ' - 'in\n' - 'effect modified. This is generally not what was intended. A ' - 'way\n' - 'around this is to use "None" as the default, and explicitly test ' - 'for\n' - 'it in the body of the function, e.g.:\n' - '\n' - ' def whats_on_the_telly(penguin=None):\n' - ' if penguin is None:\n' - ' penguin = []\n' - ' penguin.append("property of the zoo")\n' - ' return penguin\n' - '\n' - 'Function call semantics are described in more detail in section ' - 'Calls.\n' - 'A function call always assigns values to all parameters ' - 'mentioned in\n' - 'the parameter list, either from positional arguments, from ' - 'keyword\n' - 'arguments, or from default values. If the form “"*identifier"” ' - 'is\n' - 'present, it is initialized to a tuple receiving any excess ' - 'positional\n' - 'parameters, defaulting to the empty tuple. If the form\n' - '“"**identifier"” is present, it is initialized to a new ordered\n' - 'mapping receiving any excess keyword arguments, defaulting to a ' - 'new\n' - 'empty mapping of the same type. Parameters after “"*"” or\n' - '“"*identifier"” are keyword-only parameters and may only be ' - 'passed by\n' - 'keyword arguments. Parameters before “"/"” are positional-only\n' - 'parameters and may only be passed by positional arguments.\n' - '\n' - 'Changed in version 3.8: The "/" function parameter syntax may be ' - 'used\n' - 'to indicate positional-only parameters. See **PEP 570** for ' - 'details.\n' - '\n' - 'Parameters may have an *annotation* of the form “": ' - 'expression"”\n' - 'following the parameter name. Any parameter may have an ' - 'annotation,\n' - 'even those of the form "*identifier" or "**identifier". (As a ' - 'special\n' - 'case, parameters of the form "*identifier" may have an ' - 'annotation “":\n' - '*expression"”.) Functions may have “return” annotation of the ' - 'form\n' - '“"-> expression"” after the parameter list. These annotations ' - 'can be\n' - 'any valid Python expression. The presence of annotations does ' - 'not\n' - 'change the semantics of a function. See Annotations for more\n' - 'information on annotations.\n' - '\n' - 'Changed in version 3.11: Parameters of the form “"*identifier"” ' - 'may\n' - 'have an annotation “": *expression"”. See **PEP 646**.\n' - '\n' - 'It is also possible to create anonymous functions (functions not ' - 'bound\n' - 'to a name), for immediate use in expressions. This uses lambda\n' - 'expressions, described in section Lambdas. Note that the ' - 'lambda\n' - 'expression is merely a shorthand for a simplified function ' - 'definition;\n' - 'a function defined in a “"def"” statement can be passed around ' - 'or\n' - 'assigned to another name just like a function defined by a ' - 'lambda\n' - 'expression. The “"def"” form is actually more powerful since ' - 'it\n' - 'allows the execution of multiple statements and annotations.\n' - '\n' - '**Programmer’s note:** Functions are first-class objects. A ' - '“"def"”\n' - 'statement executed inside a function definition defines a local\n' - 'function that can be returned or passed around. Free variables ' - 'used\n' - 'in the nested function can access the local variables of the ' - 'function\n' - 'containing the def. See section Naming and binding for ' - 'details.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3107** - Function Annotations\n' - ' The original specification for function annotations.\n' - '\n' - ' **PEP 484** - Type Hints\n' - ' Definition of a standard meaning for annotations: type ' - 'hints.\n' - '\n' - ' **PEP 526** - Syntax for Variable Annotations\n' - ' Ability to type hint variable declarations, including ' - 'class\n' - ' variables and instance variables.\n' - '\n' - ' **PEP 563** - Postponed Evaluation of Annotations\n' - ' Support for forward references within annotations by ' - 'preserving\n' - ' annotations in a string form at runtime instead of eager\n' - ' evaluation.\n' - '\n' - ' **PEP 318** - Decorators for Functions and Methods\n' - ' Function and method decorators were introduced. Class ' - 'decorators\n' - ' were introduced in **PEP 3129**.\n', - 'global': 'The "global" statement\n' - '**********************\n' - '\n' - ' global_stmt ::= "global" identifier ("," identifier)*\n' - '\n' - 'The "global" statement causes the listed identifiers to be ' - 'interpreted\n' - 'as globals. It would be impossible to assign to a global variable\n' - 'without "global", although free variables may refer to globals ' - 'without\n' - 'being declared global.\n' - '\n' - 'The "global" statement applies to the entire scope of a function ' - 'or\n' - 'class body. A "SyntaxError" is raised if a variable is used or\n' - 'assigned to prior to its global declaration in the scope.\n' - '\n' - '**Programmer’s note:** "global" is a directive to the parser. It\n' - 'applies only to code parsed at the same time as the "global"\n' - 'statement. In particular, a "global" statement contained in a ' - 'string\n' - 'or code object supplied to the built-in "exec()" function does ' - 'not\n' - 'affect the code block *containing* the function call, and code\n' - 'contained in such a string is unaffected by "global" statements in ' - 'the\n' - 'code containing the function call. The same applies to the ' - '"eval()"\n' - 'and "compile()" functions.\n', - 'id-classes': 'Reserved classes of identifiers\n' - '*******************************\n' - '\n' - 'Certain classes of identifiers (besides keywords) have ' - 'special\n' - 'meanings. These classes are identified by the patterns of ' - 'leading and\n' - 'trailing underscore characters:\n' - '\n' - '"_*"\n' - ' Not imported by "from module import *".\n' - '\n' - '"_"\n' - ' In a "case" pattern within a "match" statement, "_" is a ' - 'soft\n' - ' keyword that denotes a wildcard.\n' - '\n' - ' Separately, the interactive interpreter makes the result of ' - 'the\n' - ' last evaluation available in the variable "_". (It is ' - 'stored in the\n' - ' "builtins" module, alongside built-in functions like ' - '"print".)\n' - '\n' - ' Elsewhere, "_" is a regular identifier. It is often used to ' - 'name\n' - ' “special” items, but it is not special to Python itself.\n' - '\n' - ' Note:\n' - '\n' - ' The name "_" is often used in conjunction with\n' - ' internationalization; refer to the documentation for the\n' - ' "gettext" module for more information on this ' - 'convention.It is\n' - ' also commonly used for unused variables.\n' - '\n' - '"__*__"\n' - ' System-defined names, informally known as “dunder” names. ' - 'These\n' - ' names are defined by the interpreter and its ' - 'implementation\n' - ' (including the standard library). Current system names are\n' - ' discussed in the Special method names section and ' - 'elsewhere. More\n' - ' will likely be defined in future versions of Python. *Any* ' - 'use of\n' - ' "__*__" names, in any context, that does not follow ' - 'explicitly\n' - ' documented use, is subject to breakage without warning.\n' - '\n' - '"__*"\n' - ' Class-private names. Names in this category, when used ' - 'within the\n' - ' context of a class definition, are re-written to use a ' - 'mangled form\n' - ' to help avoid name clashes between “private” attributes of ' - 'base and\n' - ' derived classes. See section Identifiers (Names).\n', - 'identifiers': 'Identifiers and keywords\n' - '************************\n' - '\n' - 'Identifiers (also referred to as *names*) are described by ' - 'the\n' - 'following lexical definitions.\n' - '\n' - 'The syntax of identifiers in Python is based on the Unicode ' - 'standard\n' - 'annex UAX-31, with elaboration and changes as defined below; ' - 'see also\n' - '**PEP 3131** for further details.\n' - '\n' - 'Within the ASCII range (U+0001..U+007F), the valid characters ' - 'for\n' - 'identifiers include the uppercase and lowercase letters "A" ' - 'through\n' - '"Z", the underscore "_" and, except for the first character, ' - 'the\n' - 'digits "0" through "9". Python 3.0 introduced additional ' - 'characters\n' - 'from outside the ASCII range (see **PEP 3131**). For these\n' - 'characters, the classification uses the version of the ' - 'Unicode\n' - 'Character Database as included in the "unicodedata" module.\n' - '\n' - 'Identifiers are unlimited in length. Case is significant.\n' - '\n' - ' identifier ::= xid_start xid_continue*\n' - ' id_start ::= <all characters in general categories Lu, ' - 'Ll, Lt, Lm, Lo, Nl, the underscore, and characters with the ' - 'Other_ID_Start property>\n' - ' id_continue ::= <all characters in id_start, plus ' - 'characters in the categories Mn, Mc, Nd, Pc and others with ' - 'the Other_ID_Continue property>\n' - ' xid_start ::= <all characters in id_start whose NFKC ' - 'normalization is in "id_start xid_continue*">\n' - ' xid_continue ::= <all characters in id_continue whose NFKC ' - 'normalization is in "id_continue*">\n' - '\n' - 'The Unicode category codes mentioned above stand for:\n' - '\n' - '* *Lu* - uppercase letters\n' - '\n' - '* *Ll* - lowercase letters\n' - '\n' - '* *Lt* - titlecase letters\n' - '\n' - '* *Lm* - modifier letters\n' - '\n' - '* *Lo* - other letters\n' - '\n' - '* *Nl* - letter numbers\n' - '\n' - '* *Mn* - nonspacing marks\n' - '\n' - '* *Mc* - spacing combining marks\n' - '\n' - '* *Nd* - decimal numbers\n' - '\n' - '* *Pc* - connector punctuations\n' - '\n' - '* *Other_ID_Start* - explicit list of characters in ' - 'PropList.txt to\n' - ' support backwards compatibility\n' - '\n' - '* *Other_ID_Continue* - likewise\n' - '\n' - 'All identifiers are converted into the normal form NFKC while ' - 'parsing;\n' - 'comparison of identifiers is based on NFKC.\n' - '\n' - 'A non-normative HTML file listing all valid identifier ' - 'characters for\n' - 'Unicode 16.0.0 can be found at\n' - 'https://www.unicode.org/Public/16.0.0/ucd/DerivedCoreProperties.txt\n' - '\n' - '\n' - 'Keywords\n' - '========\n' - '\n' - 'The following identifiers are used as reserved words, or ' - '*keywords* of\n' - 'the language, and cannot be used as ordinary identifiers. ' - 'They must\n' - 'be spelled exactly as written here:\n' - '\n' - ' False await else import pass\n' - ' None break except in raise\n' - ' True class finally is return\n' - ' and continue for lambda try\n' - ' as def from nonlocal while\n' - ' assert del global not with\n' - ' async elif if or yield\n' - '\n' - '\n' - 'Soft Keywords\n' - '=============\n' - '\n' - 'Added in version 3.10.\n' - '\n' - 'Some identifiers are only reserved under specific contexts. ' - 'These are\n' - 'known as *soft keywords*. The identifiers "match", "case", ' - '"type" and\n' - '"_" can syntactically act as keywords in certain contexts, ' - 'but this\n' - 'distinction is done at the parser level, not when ' - 'tokenizing.\n' - '\n' - 'As soft keywords, their use in the grammar is possible while ' - 'still\n' - 'preserving compatibility with existing code that uses these ' - 'names as\n' - 'identifier names.\n' - '\n' - '"match", "case", and "_" are used in the "match" statement. ' - '"type" is\n' - 'used in the "type" statement.\n' - '\n' - 'Changed in version 3.12: "type" is now a soft keyword.\n' - '\n' - '\n' - 'Reserved classes of identifiers\n' - '===============================\n' - '\n' - 'Certain classes of identifiers (besides keywords) have ' - 'special\n' - 'meanings. These classes are identified by the patterns of ' - 'leading and\n' - 'trailing underscore characters:\n' - '\n' - '"_*"\n' - ' Not imported by "from module import *".\n' - '\n' - '"_"\n' - ' In a "case" pattern within a "match" statement, "_" is a ' - 'soft\n' - ' keyword that denotes a wildcard.\n' - '\n' - ' Separately, the interactive interpreter makes the result ' - 'of the\n' - ' last evaluation available in the variable "_". (It is ' - 'stored in the\n' - ' "builtins" module, alongside built-in functions like ' - '"print".)\n' - '\n' - ' Elsewhere, "_" is a regular identifier. It is often used ' - 'to name\n' - ' “special” items, but it is not special to Python itself.\n' - '\n' - ' Note:\n' - '\n' - ' The name "_" is often used in conjunction with\n' - ' internationalization; refer to the documentation for ' - 'the\n' - ' "gettext" module for more information on this ' - 'convention.It is\n' - ' also commonly used for unused variables.\n' - '\n' - '"__*__"\n' - ' System-defined names, informally known as “dunder” names. ' - 'These\n' - ' names are defined by the interpreter and its ' - 'implementation\n' - ' (including the standard library). Current system names ' - 'are\n' - ' discussed in the Special method names section and ' - 'elsewhere. More\n' - ' will likely be defined in future versions of Python. ' - '*Any* use of\n' - ' "__*__" names, in any context, that does not follow ' - 'explicitly\n' - ' documented use, is subject to breakage without warning.\n' - '\n' - '"__*"\n' - ' Class-private names. Names in this category, when used ' - 'within the\n' - ' context of a class definition, are re-written to use a ' - 'mangled form\n' - ' to help avoid name clashes between “private” attributes of ' - 'base and\n' - ' derived classes. See section Identifiers (Names).\n', - 'if': 'The "if" statement\n' - '******************\n' - '\n' - 'The "if" statement is used for conditional execution:\n' - '\n' - ' if_stmt ::= "if" assignment_expression ":" suite\n' - ' ("elif" assignment_expression ":" suite)*\n' - ' ["else" ":" suite]\n' - '\n' - 'It selects exactly one of the suites by evaluating the expressions ' - 'one\n' - 'by one until one is found to be true (see section Boolean operations\n' - 'for the definition of true and false); then that suite is executed\n' - '(and no other part of the "if" statement is executed or evaluated).\n' - 'If all expressions are false, the suite of the "else" clause, if\n' - 'present, is executed.\n', - 'imaginary': 'Imaginary literals\n' - '******************\n' - '\n' - 'Imaginary literals are described by the following lexical ' - 'definitions:\n' - '\n' - ' imagnumber ::= (floatnumber | digitpart) ("j" | "J")\n' - '\n' - 'An imaginary literal yields a complex number with a real part ' - 'of 0.0.\n' - 'Complex numbers are represented as a pair of floating-point ' - 'numbers\n' - 'and have the same restrictions on their range. To create a ' - 'complex\n' - 'number with a nonzero real part, add a floating-point number to ' - 'it,\n' - 'e.g., "(3+4j)". Some examples of imaginary literals:\n' - '\n' - ' 3.14j 10.j 10j .001j 1e100j 3.14e-10j ' - '3.14_15_93j\n', - 'import': 'The "import" statement\n' - '**********************\n' - '\n' - ' import_stmt ::= "import" module ["as" identifier] ("," ' - 'module ["as" identifier])*\n' - ' | "from" relative_module "import" identifier ' - '["as" identifier]\n' - ' ("," identifier ["as" identifier])*\n' - ' | "from" relative_module "import" "(" ' - 'identifier ["as" identifier]\n' - ' ("," identifier ["as" identifier])* [","] ")"\n' - ' | "from" relative_module "import" "*"\n' - ' module ::= (identifier ".")* identifier\n' - ' relative_module ::= "."* module | "."+\n' - '\n' - 'The basic import statement (no "from" clause) is executed in two\n' - 'steps:\n' - '\n' - '1. find a module, loading and initializing it if necessary\n' - '\n' - '2. define a name or names in the local namespace for the scope ' - 'where\n' - ' the "import" statement occurs.\n' - '\n' - 'When the statement contains multiple clauses (separated by commas) ' - 'the\n' - 'two steps are carried out separately for each clause, just as ' - 'though\n' - 'the clauses had been separated out into individual import ' - 'statements.\n' - '\n' - 'The details of the first step, finding and loading modules, are\n' - 'described in greater detail in the section on the import system, ' - 'which\n' - 'also describes the various types of packages and modules that can ' - 'be\n' - 'imported, as well as all the hooks that can be used to customize ' - 'the\n' - 'import system. Note that failures in this step may indicate ' - 'either\n' - 'that the module could not be located, *or* that an error occurred\n' - 'while initializing the module, which includes execution of the\n' - 'module’s code.\n' - '\n' - 'If the requested module is retrieved successfully, it will be ' - 'made\n' - 'available in the local namespace in one of three ways:\n' - '\n' - '* If the module name is followed by "as", then the name following ' - '"as"\n' - ' is bound directly to the imported module.\n' - '\n' - '* If no other name is specified, and the module being imported is ' - 'a\n' - ' top level module, the module’s name is bound in the local ' - 'namespace\n' - ' as a reference to the imported module\n' - '\n' - '* If the module being imported is *not* a top level module, then ' - 'the\n' - ' name of the top level package that contains the module is bound ' - 'in\n' - ' the local namespace as a reference to the top level package. ' - 'The\n' - ' imported module must be accessed using its full qualified name\n' - ' rather than directly\n' - '\n' - 'The "from" form uses a slightly more complex process:\n' - '\n' - '1. find the module specified in the "from" clause, loading and\n' - ' initializing it if necessary;\n' - '\n' - '2. for each of the identifiers specified in the "import" clauses:\n' - '\n' - ' 1. check if the imported module has an attribute by that name\n' - '\n' - ' 2. if not, attempt to import a submodule with that name and ' - 'then\n' - ' check the imported module again for that attribute\n' - '\n' - ' 3. if the attribute is not found, "ImportError" is raised.\n' - '\n' - ' 4. otherwise, a reference to that value is stored in the local\n' - ' namespace, using the name in the "as" clause if it is ' - 'present,\n' - ' otherwise using the attribute name\n' - '\n' - 'Examples:\n' - '\n' - ' import foo # foo imported and bound locally\n' - ' import foo.bar.baz # foo, foo.bar, and foo.bar.baz ' - 'imported, foo bound locally\n' - ' import foo.bar.baz as fbb # foo, foo.bar, and foo.bar.baz ' - 'imported, foo.bar.baz bound as fbb\n' - ' from foo.bar import baz # foo, foo.bar, and foo.bar.baz ' - 'imported, foo.bar.baz bound as baz\n' - ' from foo import attr # foo imported and foo.attr bound as ' - 'attr\n' - '\n' - 'If the list of identifiers is replaced by a star ("\'*\'"), all ' - 'public\n' - 'names defined in the module are bound in the local namespace for ' - 'the\n' - 'scope where the "import" statement occurs.\n' - '\n' - 'The *public names* defined by a module are determined by checking ' - 'the\n' - 'module’s namespace for a variable named "__all__"; if defined, it ' - 'must\n' - 'be a sequence of strings which are names defined or imported by ' - 'that\n' - 'module. The names given in "__all__" are all considered public ' - 'and\n' - 'are required to exist. If "__all__" is not defined, the set of ' - 'public\n' - 'names includes all names found in the module’s namespace which do ' - 'not\n' - 'begin with an underscore character ("\'_\'"). "__all__" should ' - 'contain\n' - 'the entire public API. It is intended to avoid accidentally ' - 'exporting\n' - 'items that are not part of the API (such as library modules which ' - 'were\n' - 'imported and used within the module).\n' - '\n' - 'The wild card form of import — "from module import *" — is only\n' - 'allowed at the module level. Attempting to use it in class or\n' - 'function definitions will raise a "SyntaxError".\n' - '\n' - 'When specifying what module to import you do not have to specify ' - 'the\n' - 'absolute name of the module. When a module or package is ' - 'contained\n' - 'within another package it is possible to make a relative import ' - 'within\n' - 'the same top package without having to mention the package name. ' - 'By\n' - 'using leading dots in the specified module or package after "from" ' - 'you\n' - 'can specify how high to traverse up the current package hierarchy\n' - 'without specifying exact names. One leading dot means the current\n' - 'package where the module making the import exists. Two dots means ' - 'up\n' - 'one package level. Three dots is up two levels, etc. So if you ' - 'execute\n' - '"from . import mod" from a module in the "pkg" package then you ' - 'will\n' - 'end up importing "pkg.mod". If you execute "from ..subpkg2 import ' - 'mod"\n' - 'from within "pkg.subpkg1" you will import "pkg.subpkg2.mod". The\n' - 'specification for relative imports is contained in the Package\n' - 'Relative Imports section.\n' - '\n' - '"importlib.import_module()" is provided to support applications ' - 'that\n' - 'determine dynamically the modules to be loaded.\n' - '\n' - 'Raises an auditing event "import" with arguments "module", ' - '"filename",\n' - '"sys.path", "sys.meta_path", "sys.path_hooks".\n' - '\n' - '\n' - 'Future statements\n' - '=================\n' - '\n' - 'A *future statement* is a directive to the compiler that a ' - 'particular\n' - 'module should be compiled using syntax or semantics that will be\n' - 'available in a specified future release of Python where the ' - 'feature\n' - 'becomes standard.\n' - '\n' - 'The future statement is intended to ease migration to future ' - 'versions\n' - 'of Python that introduce incompatible changes to the language. ' - 'It\n' - 'allows use of the new features on a per-module basis before the\n' - 'release in which the feature becomes standard.\n' - '\n' - ' future_stmt ::= "from" "__future__" "import" feature ["as" ' - 'identifier]\n' - ' ("," feature ["as" identifier])*\n' - ' | "from" "__future__" "import" "(" feature ' - '["as" identifier]\n' - ' ("," feature ["as" identifier])* [","] ")"\n' - ' feature ::= identifier\n' - '\n' - 'A future statement must appear near the top of the module. The ' - 'only\n' - 'lines that can appear before a future statement are:\n' - '\n' - '* the module docstring (if any),\n' - '\n' - '* comments,\n' - '\n' - '* blank lines, and\n' - '\n' - '* other future statements.\n' - '\n' - 'The only feature that requires using the future statement is\n' - '"annotations" (see **PEP 563**).\n' - '\n' - 'All historical features enabled by the future statement are still\n' - 'recognized by Python 3. The list includes "absolute_import",\n' - '"division", "generators", "generator_stop", "unicode_literals",\n' - '"print_function", "nested_scopes" and "with_statement". They are ' - 'all\n' - 'redundant because they are always enabled, and only kept for ' - 'backwards\n' - 'compatibility.\n' - '\n' - 'A future statement is recognized and treated specially at compile\n' - 'time: Changes to the semantics of core constructs are often\n' - 'implemented by generating different code. It may even be the ' - 'case\n' - 'that a new feature introduces new incompatible syntax (such as a ' - 'new\n' - 'reserved word), in which case the compiler may need to parse the\n' - 'module differently. Such decisions cannot be pushed off until\n' - 'runtime.\n' - '\n' - 'For any given release, the compiler knows which feature names ' - 'have\n' - 'been defined, and raises a compile-time error if a future ' - 'statement\n' - 'contains a feature not known to it.\n' - '\n' - 'The direct runtime semantics are the same as for any import ' - 'statement:\n' - 'there is a standard module "__future__", described later, and it ' - 'will\n' - 'be imported in the usual way at the time the future statement is\n' - 'executed.\n' - '\n' - 'The interesting runtime semantics depend on the specific feature\n' - 'enabled by the future statement.\n' - '\n' - 'Note that there is nothing special about the statement:\n' - '\n' - ' import __future__ [as name]\n' - '\n' - 'That is not a future statement; it’s an ordinary import statement ' - 'with\n' - 'no special semantics or syntax restrictions.\n' - '\n' - 'Code compiled by calls to the built-in functions "exec()" and\n' - '"compile()" that occur in a module "M" containing a future ' - 'statement\n' - 'will, by default, use the new syntax or semantics associated with ' - 'the\n' - 'future statement. This can be controlled by optional arguments ' - 'to\n' - '"compile()" — see the documentation of that function for details.\n' - '\n' - 'A future statement typed at an interactive interpreter prompt ' - 'will\n' - 'take effect for the rest of the interpreter session. If an\n' - 'interpreter is started with the "-i" option, is passed a script ' - 'name\n' - 'to execute, and the script includes a future statement, it will be ' - 'in\n' - 'effect in the interactive session started after the script is\n' - 'executed.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 236** - Back to the __future__\n' - ' The original proposal for the __future__ mechanism.\n', - 'in': 'Membership test operations\n' - '**************************\n' - '\n' - 'The operators "in" and "not in" test for membership. "x in s"\n' - 'evaluates to "True" if *x* is a member of *s*, and "False" otherwise.\n' - '"x not in s" returns the negation of "x in s". All built-in ' - 'sequences\n' - 'and set types support this as well as dictionary, for which "in" ' - 'tests\n' - 'whether the dictionary has a given key. For container types such as\n' - 'list, tuple, set, frozenset, dict, or collections.deque, the\n' - 'expression "x in y" is equivalent to "any(x is e or x == e for e in\n' - 'y)".\n' - '\n' - 'For the string and bytes types, "x in y" is "True" if and only if *x*\n' - 'is a substring of *y*. An equivalent test is "y.find(x) != -1".\n' - 'Empty strings are always considered to be a substring of any other\n' - 'string, so """ in "abc"" will return "True".\n' - '\n' - 'For user-defined classes which define the "__contains__()" method, "x\n' - 'in y" returns "True" if "y.__contains__(x)" returns a true value, and\n' - '"False" otherwise.\n' - '\n' - 'For user-defined classes which do not define "__contains__()" but do\n' - 'define "__iter__()", "x in y" is "True" if some value "z", for which\n' - 'the expression "x is z or x == z" is true, is produced while ' - 'iterating\n' - 'over "y". If an exception is raised during the iteration, it is as if\n' - '"in" raised that exception.\n' - '\n' - 'Lastly, the old-style iteration protocol is tried: if a class defines\n' - '"__getitem__()", "x in y" is "True" if and only if there is a non-\n' - 'negative integer index *i* such that "x is y[i] or x == y[i]", and no\n' - 'lower integer index raises the "IndexError" exception. (If any other\n' - 'exception is raised, it is as if "in" raised that exception).\n' - '\n' - 'The operator "not in" is defined to have the inverse truth value of\n' - '"in".\n', - 'integers': 'Integer literals\n' - '****************\n' - '\n' - 'Integer literals are described by the following lexical ' - 'definitions:\n' - '\n' - ' integer ::= decinteger | bininteger | octinteger | ' - 'hexinteger\n' - ' decinteger ::= nonzerodigit (["_"] digit)* | "0"+ (["_"] ' - '"0")*\n' - ' bininteger ::= "0" ("b" | "B") (["_"] bindigit)+\n' - ' octinteger ::= "0" ("o" | "O") (["_"] octdigit)+\n' - ' hexinteger ::= "0" ("x" | "X") (["_"] hexdigit)+\n' - ' nonzerodigit ::= "1"..."9"\n' - ' digit ::= "0"..."9"\n' - ' bindigit ::= "0" | "1"\n' - ' octdigit ::= "0"..."7"\n' - ' hexdigit ::= digit | "a"..."f" | "A"..."F"\n' - '\n' - 'There is no limit for the length of integer literals apart from ' - 'what\n' - 'can be stored in available memory.\n' - '\n' - 'Underscores are ignored for determining the numeric value of ' - 'the\n' - 'literal. They can be used to group digits for enhanced ' - 'readability.\n' - 'One underscore can occur between digits, and after base ' - 'specifiers\n' - 'like "0x".\n' - '\n' - 'Note that leading zeros in a non-zero decimal number are not ' - 'allowed.\n' - 'This is for disambiguation with C-style octal literals, which ' - 'Python\n' - 'used before version 3.0.\n' - '\n' - 'Some examples of integer literals:\n' - '\n' - ' 7 2147483647 0o177 0b100110111\n' - ' 3 79228162514264337593543950336 0o377 0xdeadbeef\n' - ' 100_000_000_000 0b_1110_0101\n' - '\n' - 'Changed in version 3.6: Underscores are now allowed for ' - 'grouping\n' - 'purposes in literals.\n', - 'lambda': 'Lambdas\n' - '*******\n' - '\n' - ' lambda_expr ::= "lambda" [parameter_list] ":" expression\n' - '\n' - 'Lambda expressions (sometimes called lambda forms) are used to ' - 'create\n' - 'anonymous functions. The expression "lambda parameters: ' - 'expression"\n' - 'yields a function object. The unnamed object behaves like a ' - 'function\n' - 'object defined with:\n' - '\n' - ' def <lambda>(parameters):\n' - ' return expression\n' - '\n' - 'See section Function definitions for the syntax of parameter ' - 'lists.\n' - 'Note that functions created with lambda expressions cannot ' - 'contain\n' - 'statements or annotations.\n', - 'lists': 'List displays\n' - '*************\n' - '\n' - 'A list display is a possibly empty series of expressions enclosed ' - 'in\n' - 'square brackets:\n' - '\n' - ' list_display ::= "[" [flexible_expression_list | comprehension] ' - '"]"\n' - '\n' - 'A list display yields a new list object, the contents being ' - 'specified\n' - 'by either a list of expressions or a comprehension. When a comma-\n' - 'separated list of expressions is supplied, its elements are ' - 'evaluated\n' - 'from left to right and placed into the list object in that order.\n' - 'When a comprehension is supplied, the list is constructed from the\n' - 'elements resulting from the comprehension.\n', - 'naming': 'Naming and binding\n' - '******************\n' - '\n' - '\n' - 'Binding of names\n' - '================\n' - '\n' - '*Names* refer to objects. Names are introduced by name binding\n' - 'operations.\n' - '\n' - 'The following constructs bind names:\n' - '\n' - '* formal parameters to functions,\n' - '\n' - '* class definitions,\n' - '\n' - '* function definitions,\n' - '\n' - '* assignment expressions,\n' - '\n' - '* targets that are identifiers if occurring in an assignment:\n' - '\n' - ' * "for" loop header,\n' - '\n' - ' * after "as" in a "with" statement, "except" clause, "except*"\n' - ' clause, or in the as-pattern in structural pattern matching,\n' - '\n' - ' * in a capture pattern in structural pattern matching\n' - '\n' - '* "import" statements.\n' - '\n' - '* "type" statements.\n' - '\n' - '* type parameter lists.\n' - '\n' - 'The "import" statement of the form "from ... import *" binds all ' - 'names\n' - 'defined in the imported module, except those beginning with an\n' - 'underscore. This form may only be used at the module level.\n' - '\n' - 'A target occurring in a "del" statement is also considered bound ' - 'for\n' - 'this purpose (though the actual semantics are to unbind the ' - 'name).\n' - '\n' - 'Each assignment or import statement occurs within a block defined ' - 'by a\n' - 'class or function definition or at the module level (the ' - 'top-level\n' - 'code block).\n' - '\n' - 'If a name is bound in a block, it is a local variable of that ' - 'block,\n' - 'unless declared as "nonlocal" or "global". If a name is bound at ' - 'the\n' - 'module level, it is a global variable. (The variables of the ' - 'module\n' - 'code block are local and global.) If a variable is used in a ' - 'code\n' - 'block but not defined there, it is a *free variable*.\n' - '\n' - 'Each occurrence of a name in the program text refers to the ' - '*binding*\n' - 'of that name established by the following name resolution rules.\n' - '\n' - '\n' - 'Resolution of names\n' - '===================\n' - '\n' - 'A *scope* defines the visibility of a name within a block. If a ' - 'local\n' - 'variable is defined in a block, its scope includes that block. If ' - 'the\n' - 'definition occurs in a function block, the scope extends to any ' - 'blocks\n' - 'contained within the defining one, unless a contained block ' - 'introduces\n' - 'a different binding for the name.\n' - '\n' - 'When a name is used in a code block, it is resolved using the ' - 'nearest\n' - 'enclosing scope. The set of all such scopes visible to a code ' - 'block\n' - 'is called the block’s *environment*.\n' - '\n' - 'When a name is not found at all, a "NameError" exception is ' - 'raised. If\n' - 'the current scope is a function scope, and the name refers to a ' - 'local\n' - 'variable that has not yet been bound to a value at the point where ' - 'the\n' - 'name is used, an "UnboundLocalError" exception is raised.\n' - '"UnboundLocalError" is a subclass of "NameError".\n' - '\n' - 'If a name binding operation occurs anywhere within a code block, ' - 'all\n' - 'uses of the name within the block are treated as references to ' - 'the\n' - 'current block. This can lead to errors when a name is used within ' - 'a\n' - 'block before it is bound. This rule is subtle. Python lacks\n' - 'declarations and allows name binding operations to occur anywhere\n' - 'within a code block. The local variables of a code block can be\n' - 'determined by scanning the entire text of the block for name ' - 'binding\n' - 'operations. See the FAQ entry on UnboundLocalError for examples.\n' - '\n' - 'If the "global" statement occurs within a block, all uses of the ' - 'names\n' - 'specified in the statement refer to the bindings of those names in ' - 'the\n' - 'top-level namespace. Names are resolved in the top-level ' - 'namespace by\n' - 'searching the global namespace, i.e. the namespace of the module\n' - 'containing the code block, and the builtins namespace, the ' - 'namespace\n' - 'of the module "builtins". The global namespace is searched ' - 'first. If\n' - 'the names are not found there, the builtins namespace is searched\n' - 'next. If the names are also not found in the builtins namespace, ' - 'new\n' - 'variables are created in the global namespace. The global ' - 'statement\n' - 'must precede all uses of the listed names.\n' - '\n' - 'The "global" statement has the same scope as a name binding ' - 'operation\n' - 'in the same block. If the nearest enclosing scope for a free ' - 'variable\n' - 'contains a global statement, the free variable is treated as a ' - 'global.\n' - '\n' - 'The "nonlocal" statement causes corresponding names to refer to\n' - 'previously bound variables in the nearest enclosing function ' - 'scope.\n' - '"SyntaxError" is raised at compile time if the given name does ' - 'not\n' - 'exist in any enclosing function scope. Type parameters cannot be\n' - 'rebound with the "nonlocal" statement.\n' - '\n' - 'The namespace for a module is automatically created the first time ' - 'a\n' - 'module is imported. The main module for a script is always ' - 'called\n' - '"__main__".\n' - '\n' - 'Class definition blocks and arguments to "exec()" and "eval()" ' - 'are\n' - 'special in the context of name resolution. A class definition is ' - 'an\n' - 'executable statement that may use and define names. These ' - 'references\n' - 'follow the normal rules for name resolution with an exception ' - 'that\n' - 'unbound local variables are looked up in the global namespace. ' - 'The\n' - 'namespace of the class definition becomes the attribute dictionary ' - 'of\n' - 'the class. The scope of names defined in a class block is limited ' - 'to\n' - 'the class block; it does not extend to the code blocks of ' - 'methods.\n' - 'This includes comprehensions and generator expressions, but it ' - 'does\n' - 'not include annotation scopes, which have access to their ' - 'enclosing\n' - 'class scopes. This means that the following will fail:\n' - '\n' - ' class A:\n' - ' a = 42\n' - ' b = list(a + i for i in range(10))\n' - '\n' - 'However, the following will succeed:\n' - '\n' - ' class A:\n' - ' type Alias = Nested\n' - ' class Nested: pass\n' - '\n' - " print(A.Alias.__value__) # <type 'A.Nested'>\n" - '\n' - '\n' - 'Annotation scopes\n' - '=================\n' - '\n' - '*Annotations*, type parameter lists and "type" statements ' - 'introduce\n' - '*annotation scopes*, which behave mostly like function scopes, ' - 'but\n' - 'with some exceptions discussed below.\n' - '\n' - 'Annotation scopes are used in the following contexts:\n' - '\n' - '* *Function annotations*.\n' - '\n' - '* *Variable annotations*.\n' - '\n' - '* Type parameter lists for generic type aliases.\n' - '\n' - '* Type parameter lists for generic functions. A generic ' - 'function’s\n' - ' annotations are executed within the annotation scope, but its\n' - ' defaults and decorators are not.\n' - '\n' - '* Type parameter lists for generic classes. A generic class’s ' - 'base\n' - ' classes and keyword arguments are executed within the ' - 'annotation\n' - ' scope, but its decorators are not.\n' - '\n' - '* The bounds, constraints, and default values for type parameters\n' - ' (lazily evaluated).\n' - '\n' - '* The value of type aliases (lazily evaluated).\n' - '\n' - 'Annotation scopes differ from function scopes in the following ' - 'ways:\n' - '\n' - '* Annotation scopes have access to their enclosing class ' - 'namespace. If\n' - ' an annotation scope is immediately within a class scope, or ' - 'within\n' - ' another annotation scope that is immediately within a class ' - 'scope,\n' - ' the code in the annotation scope can use names defined in the ' - 'class\n' - ' scope as if it were executed directly within the class body. ' - 'This\n' - ' contrasts with regular functions defined within classes, which\n' - ' cannot access names defined in the class scope.\n' - '\n' - '* Expressions in annotation scopes cannot contain "yield", "yield\n' - ' from", "await", or ":=" expressions. (These expressions are ' - 'allowed\n' - ' in other scopes contained within the annotation scope.)\n' - '\n' - '* Names defined in annotation scopes cannot be rebound with ' - '"nonlocal"\n' - ' statements in inner scopes. This includes only type parameters, ' - 'as\n' - ' no other syntactic elements that can appear within annotation ' - 'scopes\n' - ' can introduce new names.\n' - '\n' - '* While annotation scopes have an internal name, that name is not\n' - ' reflected in the *qualified name* of objects defined within the\n' - ' scope. Instead, the "__qualname__" of such objects is as if the\n' - ' object were defined in the enclosing scope.\n' - '\n' - 'Added in version 3.12: Annotation scopes were introduced in ' - 'Python\n' - '3.12 as part of **PEP 695**.\n' - '\n' - 'Changed in version 3.13: Annotation scopes are also used for type\n' - 'parameter defaults, as introduced by **PEP 696**.\n' - '\n' - 'Changed in version 3.14: Annotation scopes are now also used for\n' - 'annotations, as specified in **PEP 649** and **PEP 749**.\n' - '\n' - '\n' - 'Lazy evaluation\n' - '===============\n' - '\n' - 'Most annotation scopes are *lazily evaluated*. This includes\n' - 'annotations, the values of type aliases created through the ' - '"type"\n' - 'statement, and the bounds, constraints, and default values of ' - 'type\n' - 'variables created through the type parameter syntax. This means ' - 'that\n' - 'they are not evaluated when the type alias or type variable is\n' - 'created, or when the object carrying annotations is created. ' - 'Instead,\n' - 'they are only evaluated when necessary, for example when the\n' - '"__value__" attribute on a type alias is accessed.\n' - '\n' - 'Example:\n' - '\n' - ' >>> type Alias = 1/0\n' - ' >>> Alias.__value__\n' - ' Traceback (most recent call last):\n' - ' ...\n' - ' ZeroDivisionError: division by zero\n' - ' >>> def func[T: 1/0](): pass\n' - ' >>> T = func.__type_params__[0]\n' - ' >>> T.__bound__\n' - ' Traceback (most recent call last):\n' - ' ...\n' - ' ZeroDivisionError: division by zero\n' - '\n' - 'Here the exception is raised only when the "__value__" attribute ' - 'of\n' - 'the type alias or the "__bound__" attribute of the type variable ' - 'is\n' - 'accessed.\n' - '\n' - 'This behavior is primarily useful for references to types that ' - 'have\n' - 'not yet been defined when the type alias or type variable is ' - 'created.\n' - 'For example, lazy evaluation enables creation of mutually ' - 'recursive\n' - 'type aliases:\n' - '\n' - ' from typing import Literal\n' - '\n' - ' type SimpleExpr = int | Parenthesized\n' - ' type Parenthesized = tuple[Literal["("], Expr, Literal[")"]]\n' - ' type Expr = SimpleExpr | tuple[SimpleExpr, Literal["+", "-"], ' - 'Expr]\n' - '\n' - 'Lazily evaluated values are evaluated in annotation scope, which ' - 'means\n' - 'that names that appear inside the lazily evaluated value are ' - 'looked up\n' - 'as if they were used in the immediately enclosing scope.\n' - '\n' - 'Added in version 3.12.\n' - '\n' - '\n' - 'Builtins and restricted execution\n' - '=================================\n' - '\n' - '**CPython implementation detail:** Users should not touch\n' - '"__builtins__"; it is strictly an implementation detail. Users\n' - 'wanting to override values in the builtins namespace should ' - '"import"\n' - 'the "builtins" module and modify its attributes appropriately.\n' - '\n' - 'The builtins namespace associated with the execution of a code ' - 'block\n' - 'is actually found by looking up the name "__builtins__" in its ' - 'global\n' - 'namespace; this should be a dictionary or a module (in the latter ' - 'case\n' - 'the module’s dictionary is used). By default, when in the ' - '"__main__"\n' - 'module, "__builtins__" is the built-in module "builtins"; when in ' - 'any\n' - 'other module, "__builtins__" is an alias for the dictionary of ' - 'the\n' - '"builtins" module itself.\n' - '\n' - '\n' - 'Interaction with dynamic features\n' - '=================================\n' - '\n' - 'Name resolution of free variables occurs at runtime, not at ' - 'compile\n' - 'time. This means that the following code will print 42:\n' - '\n' - ' i = 10\n' - ' def f():\n' - ' print(i)\n' - ' i = 42\n' - ' f()\n' - '\n' - 'The "eval()" and "exec()" functions do not have access to the ' - 'full\n' - 'environment for resolving names. Names may be resolved in the ' - 'local\n' - 'and global namespaces of the caller. Free variables are not ' - 'resolved\n' - 'in the nearest enclosing namespace, but in the global namespace. ' - '[1]\n' - 'The "exec()" and "eval()" functions have optional arguments to\n' - 'override the global and local namespace. If only one namespace ' - 'is\n' - 'specified, it is used for both.\n', - 'nonlocal': 'The "nonlocal" statement\n' - '************************\n' - '\n' - ' nonlocal_stmt ::= "nonlocal" identifier ("," identifier)*\n' - '\n' - 'When the definition of a function or class is nested (enclosed) ' - 'within\n' - 'the definitions of other functions, its nonlocal scopes are the ' - 'local\n' - 'scopes of the enclosing functions. The "nonlocal" statement ' - 'causes the\n' - 'listed identifiers to refer to names previously bound in ' - 'nonlocal\n' - 'scopes. It allows encapsulated code to rebind such nonlocal\n' - 'identifiers. If a name is bound in more than one nonlocal ' - 'scope, the\n' - 'nearest binding is used. If a name is not bound in any nonlocal ' - 'scope,\n' - 'or if there is no nonlocal scope, a "SyntaxError" is raised.\n' - '\n' - 'The "nonlocal" statement applies to the entire scope of a ' - 'function or\n' - 'class body. A "SyntaxError" is raised if a variable is used or\n' - 'assigned to prior to its nonlocal declaration in the scope.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3104** - Access to Names in Outer Scopes\n' - ' The specification for the "nonlocal" statement.\n' - '\n' - '**Programmer’s note:** "nonlocal" is a directive to the parser ' - 'and\n' - 'applies only to code parsed along with it. See the note for ' - 'the\n' - '"global" statement.\n', - 'numbers': 'Numeric literals\n' - '****************\n' - '\n' - 'There are three types of numeric literals: integers, ' - 'floating-point\n' - 'numbers, and imaginary numbers. There are no complex literals\n' - '(complex numbers can be formed by adding a real number and an\n' - 'imaginary number).\n' - '\n' - 'Note that numeric literals do not include a sign; a phrase like ' - '"-1"\n' - 'is actually an expression composed of the unary operator ‘"-"’ ' - 'and the\n' - 'literal "1".\n', - 'numeric-types': 'Emulating numeric types\n' - '***********************\n' - '\n' - 'The following methods can be defined to emulate numeric ' - 'objects.\n' - 'Methods corresponding to operations that are not supported ' - 'by the\n' - 'particular kind of number implemented (e.g., bitwise ' - 'operations for\n' - 'non-integral numbers) should be left undefined.\n' - '\n' - 'object.__add__(self, other)\n' - 'object.__sub__(self, other)\n' - 'object.__mul__(self, other)\n' - 'object.__matmul__(self, other)\n' - 'object.__truediv__(self, other)\n' - 'object.__floordiv__(self, other)\n' - 'object.__mod__(self, other)\n' - 'object.__divmod__(self, other)\n' - 'object.__pow__(self, other[, modulo])\n' - 'object.__lshift__(self, other)\n' - 'object.__rshift__(self, other)\n' - 'object.__and__(self, other)\n' - 'object.__xor__(self, other)\n' - 'object.__or__(self, other)\n' - '\n' - ' These methods are called to implement the binary ' - 'arithmetic\n' - ' operations ("+", "-", "*", "@", "/", "//", "%", ' - '"divmod()",\n' - ' "pow()", "**", "<<", ">>", "&", "^", "|"). For ' - 'instance, to\n' - ' evaluate the expression "x + y", where *x* is an ' - 'instance of a\n' - ' class that has an "__add__()" method, ' - '"type(x).__add__(x, y)" is\n' - ' called. The "__divmod__()" method should be the ' - 'equivalent to\n' - ' using "__floordiv__()" and "__mod__()"; it should not be ' - 'related to\n' - ' "__truediv__()". Note that "__pow__()" should be ' - 'defined to accept\n' - ' an optional third argument if the ternary version of the ' - 'built-in\n' - ' "pow()" function is to be supported.\n' - '\n' - ' If one of those methods does not support the operation ' - 'with the\n' - ' supplied arguments, it should return "NotImplemented".\n' - '\n' - 'object.__radd__(self, other)\n' - 'object.__rsub__(self, other)\n' - 'object.__rmul__(self, other)\n' - 'object.__rmatmul__(self, other)\n' - 'object.__rtruediv__(self, other)\n' - 'object.__rfloordiv__(self, other)\n' - 'object.__rmod__(self, other)\n' - 'object.__rdivmod__(self, other)\n' - 'object.__rpow__(self, other[, modulo])\n' - 'object.__rlshift__(self, other)\n' - 'object.__rrshift__(self, other)\n' - 'object.__rand__(self, other)\n' - 'object.__rxor__(self, other)\n' - 'object.__ror__(self, other)\n' - '\n' - ' These methods are called to implement the binary ' - 'arithmetic\n' - ' operations ("+", "-", "*", "@", "/", "//", "%", ' - '"divmod()",\n' - ' "pow()", "**", "<<", ">>", "&", "^", "|") with reflected ' - '(swapped)\n' - ' operands. These functions are only called if the ' - 'operands are of\n' - ' different types, when the left operand does not support ' - 'the\n' - ' corresponding operation [3], or the right operand’s ' - 'class is\n' - ' derived from the left operand’s class. [4] For instance, ' - 'to\n' - ' evaluate the expression "x - y", where *y* is an ' - 'instance of a\n' - ' class that has an "__rsub__()" method, ' - '"type(y).__rsub__(y, x)" is\n' - ' called if "type(x).__sub__(x, y)" returns ' - '"NotImplemented" or\n' - ' "type(y)" is a subclass of "type(x)". [5]\n' - '\n' - ' Note that ternary "pow()" will not try calling ' - '"__rpow__()" (the\n' - ' coercion rules would become too complicated).\n' - '\n' - ' Note:\n' - '\n' - ' If the right operand’s type is a subclass of the left ' - 'operand’s\n' - ' type and that subclass provides a different ' - 'implementation of the\n' - ' reflected method for the operation, this method will ' - 'be called\n' - ' before the left operand’s non-reflected method. This ' - 'behavior\n' - ' allows subclasses to override their ancestors’ ' - 'operations.\n' - '\n' - 'object.__iadd__(self, other)\n' - 'object.__isub__(self, other)\n' - 'object.__imul__(self, other)\n' - 'object.__imatmul__(self, other)\n' - 'object.__itruediv__(self, other)\n' - 'object.__ifloordiv__(self, other)\n' - 'object.__imod__(self, other)\n' - 'object.__ipow__(self, other[, modulo])\n' - 'object.__ilshift__(self, other)\n' - 'object.__irshift__(self, other)\n' - 'object.__iand__(self, other)\n' - 'object.__ixor__(self, other)\n' - 'object.__ior__(self, other)\n' - '\n' - ' These methods are called to implement the augmented ' - 'arithmetic\n' - ' assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", ' - '"**=",\n' - ' "<<=", ">>=", "&=", "^=", "|="). These methods should ' - 'attempt to\n' - ' do the operation in-place (modifying *self*) and return ' - 'the result\n' - ' (which could be, but does not have to be, *self*). If a ' - 'specific\n' - ' method is not defined, or if that method returns ' - '"NotImplemented",\n' - ' the augmented assignment falls back to the normal ' - 'methods. For\n' - ' instance, if *x* is an instance of a class with an ' - '"__iadd__()"\n' - ' method, "x += y" is equivalent to "x = x.__iadd__(y)" . ' - 'If\n' - ' "__iadd__()" does not exist, or if "x.__iadd__(y)" ' - 'returns\n' - ' "NotImplemented", "x.__add__(y)" and "y.__radd__(x)" ' - 'are\n' - ' considered, as with the evaluation of "x + y". In ' - 'certain\n' - ' situations, augmented assignment can result in ' - 'unexpected errors\n' - ' (see Why does a_tuple[i] += [‘item’] raise an exception ' - 'when the\n' - ' addition works?), but this behavior is in fact part of ' - 'the data\n' - ' model.\n' - '\n' - 'object.__neg__(self)\n' - 'object.__pos__(self)\n' - 'object.__abs__(self)\n' - 'object.__invert__(self)\n' - '\n' - ' Called to implement the unary arithmetic operations ' - '("-", "+",\n' - ' "abs()" and "~").\n' - '\n' - 'object.__complex__(self)\n' - 'object.__int__(self)\n' - 'object.__float__(self)\n' - '\n' - ' Called to implement the built-in functions "complex()", ' - '"int()" and\n' - ' "float()". Should return a value of the appropriate ' - 'type.\n' - '\n' - 'object.__index__(self)\n' - '\n' - ' Called to implement "operator.index()", and whenever ' - 'Python needs\n' - ' to losslessly convert the numeric object to an integer ' - 'object (such\n' - ' as in slicing, or in the built-in "bin()", "hex()" and ' - '"oct()"\n' - ' functions). Presence of this method indicates that the ' - 'numeric\n' - ' object is an integer type. Must return an integer.\n' - '\n' - ' If "__int__()", "__float__()" and "__complex__()" are ' - 'not defined\n' - ' then corresponding built-in functions "int()", "float()" ' - 'and\n' - ' "complex()" fall back to "__index__()".\n' - '\n' - 'object.__round__(self[, ndigits])\n' - 'object.__trunc__(self)\n' - 'object.__floor__(self)\n' - 'object.__ceil__(self)\n' - '\n' - ' Called to implement the built-in function "round()" and ' - '"math"\n' - ' functions "trunc()", "floor()" and "ceil()". Unless ' - '*ndigits* is\n' - ' passed to "__round__()" all these methods should return ' - 'the value\n' - ' of the object truncated to an "Integral" (typically an ' - '"int").\n' - '\n' - ' Changed in version 3.14: "int()" no longer delegates to ' - 'the\n' - ' "__trunc__()" method.\n', - 'objects': 'Objects, values and types\n' - '*************************\n' - '\n' - '*Objects* are Python’s abstraction for data. All data in a ' - 'Python\n' - 'program is represented by objects or by relations between ' - 'objects. (In\n' - 'a sense, and in conformance to Von Neumann’s model of a “stored\n' - 'program computer”, code is also represented by objects.)\n' - '\n' - 'Every object has an identity, a type and a value. An object’s\n' - '*identity* never changes once it has been created; you may think ' - 'of it\n' - 'as the object’s address in memory. The "is" operator compares ' - 'the\n' - 'identity of two objects; the "id()" function returns an integer\n' - 'representing its identity.\n' - '\n' - '**CPython implementation detail:** For CPython, "id(x)" is the ' - 'memory\n' - 'address where "x" is stored.\n' - '\n' - 'An object’s type determines the operations that the object ' - 'supports\n' - '(e.g., “does it have a length?”) and also defines the possible ' - 'values\n' - 'for objects of that type. The "type()" function returns an ' - 'object’s\n' - 'type (which is an object itself). Like its identity, an ' - 'object’s\n' - '*type* is also unchangeable. [1]\n' - '\n' - 'The *value* of some objects can change. Objects whose value can\n' - 'change are said to be *mutable*; objects whose value is ' - 'unchangeable\n' - 'once they are created are called *immutable*. (The value of an\n' - 'immutable container object that contains a reference to a ' - 'mutable\n' - 'object can change when the latter’s value is changed; however ' - 'the\n' - 'container is still considered immutable, because the collection ' - 'of\n' - 'objects it contains cannot be changed. So, immutability is not\n' - 'strictly the same as having an unchangeable value, it is more ' - 'subtle.)\n' - 'An object’s mutability is determined by its type; for instance,\n' - 'numbers, strings and tuples are immutable, while dictionaries ' - 'and\n' - 'lists are mutable.\n' - '\n' - 'Objects are never explicitly destroyed; however, when they ' - 'become\n' - 'unreachable they may be garbage-collected. An implementation is\n' - 'allowed to postpone garbage collection or omit it altogether — it ' - 'is a\n' - 'matter of implementation quality how garbage collection is\n' - 'implemented, as long as no objects are collected that are still\n' - 'reachable.\n' - '\n' - '**CPython implementation detail:** CPython currently uses a ' - 'reference-\n' - 'counting scheme with (optional) delayed detection of cyclically ' - 'linked\n' - 'garbage, which collects most objects as soon as they become\n' - 'unreachable, but is not guaranteed to collect garbage containing\n' - 'circular references. See the documentation of the "gc" module ' - 'for\n' - 'information on controlling the collection of cyclic garbage. ' - 'Other\n' - 'implementations act differently and CPython may change. Do not ' - 'depend\n' - 'on immediate finalization of objects when they become unreachable ' - '(so\n' - 'you should always close files explicitly).\n' - '\n' - 'Note that the use of the implementation’s tracing or debugging\n' - 'facilities may keep objects alive that would normally be ' - 'collectable.\n' - 'Also note that catching an exception with a "try"…"except" ' - 'statement\n' - 'may keep objects alive.\n' - '\n' - 'Some objects contain references to “external” resources such as ' - 'open\n' - 'files or windows. It is understood that these resources are ' - 'freed\n' - 'when the object is garbage-collected, but since garbage ' - 'collection is\n' - 'not guaranteed to happen, such objects also provide an explicit ' - 'way to\n' - 'release the external resource, usually a "close()" method. ' - 'Programs\n' - 'are strongly recommended to explicitly close such objects. The\n' - '"try"…"finally" statement and the "with" statement provide ' - 'convenient\n' - 'ways to do this.\n' - '\n' - 'Some objects contain references to other objects; these are ' - 'called\n' - '*containers*. Examples of containers are tuples, lists and\n' - 'dictionaries. The references are part of a container’s value. ' - 'In\n' - 'most cases, when we talk about the value of a container, we imply ' - 'the\n' - 'values, not the identities of the contained objects; however, ' - 'when we\n' - 'talk about the mutability of a container, only the identities of ' - 'the\n' - 'immediately contained objects are implied. So, if an immutable\n' - 'container (like a tuple) contains a reference to a mutable ' - 'object, its\n' - 'value changes if that mutable object is changed.\n' - '\n' - 'Types affect almost all aspects of object behavior. Even the\n' - 'importance of object identity is affected in some sense: for ' - 'immutable\n' - 'types, operations that compute new values may actually return a\n' - 'reference to any existing object with the same type and value, ' - 'while\n' - 'for mutable objects this is not allowed. For example, after "a = ' - '1; b\n' - '= 1", *a* and *b* may or may not refer to the same object with ' - 'the\n' - 'value one, depending on the implementation. This is because "int" ' - 'is\n' - 'an immutable type, so the reference to "1" can be reused. This\n' - 'behaviour depends on the implementation used, so should not be ' - 'relied\n' - 'upon, but is something to be aware of when making use of object\n' - 'identity tests. However, after "c = []; d = []", *c* and *d* are\n' - 'guaranteed to refer to two different, unique, newly created ' - 'empty\n' - 'lists. (Note that "e = f = []" assigns the *same* object to both ' - '*e*\n' - 'and *f*.)\n', - 'operator-summary': 'Operator precedence\n' - '*******************\n' - '\n' - 'The following table summarizes the operator precedence ' - 'in Python, from\n' - 'highest precedence (most binding) to lowest precedence ' - '(least\n' - 'binding). Operators in the same box have the same ' - 'precedence. Unless\n' - 'the syntax is explicitly given, operators are binary. ' - 'Operators in\n' - 'the same box group left to right (except for ' - 'exponentiation and\n' - 'conditional expressions, which group from right to ' - 'left).\n' - '\n' - 'Note that comparisons, membership tests, and identity ' - 'tests, all have\n' - 'the same precedence and have a left-to-right chaining ' - 'feature as\n' - 'described in the Comparisons section.\n' - '\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| Operator | ' - 'Description |\n' - '|=================================================|=======================================|\n' - '| "(expressions...)", "[expressions...]", "{key: | ' - 'Binding or parenthesized expression, |\n' - '| value...}", "{expressions...}" | list ' - 'display, dictionary display, set |\n' - '| | ' - 'display |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "x[index]", "x[index:index]", | ' - 'Subscription, slicing, call, |\n' - '| "x(arguments...)", "x.attribute" | ' - 'attribute reference |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "await x" | ' - 'Await expression |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "**" | ' - 'Exponentiation [5] |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "+x", "-x", "~x" | ' - 'Positive, negative, bitwise NOT |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "*", "@", "/", "//", "%" | ' - 'Multiplication, matrix |\n' - '| | ' - 'multiplication, division, floor |\n' - '| | ' - 'division, remainder [6] |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "+", "-" | ' - 'Addition and subtraction |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "<<", ">>" | ' - 'Shifts |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "&" | ' - 'Bitwise AND |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "^" | ' - 'Bitwise XOR |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "|" | ' - 'Bitwise OR |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "in", "not in", "is", "is not", "<", "<=", ">", | ' - 'Comparisons, including membership |\n' - '| ">=", "!=", "==" | ' - 'tests and identity tests |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "not x" | ' - 'Boolean NOT |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "and" | ' - 'Boolean AND |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "or" | ' - 'Boolean OR |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "if" – "else" | ' - 'Conditional expression |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| "lambda" | ' - 'Lambda expression |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '| ":=" | ' - 'Assignment expression |\n' - '+-------------------------------------------------+---------------------------------------+\n' - '\n' - '-[ Footnotes ]-\n' - '\n' - '[1] While "abs(x%y) < abs(y)" is true mathematically, ' - 'for floats it\n' - ' may not be true numerically due to roundoff. For ' - 'example, and\n' - ' assuming a platform on which a Python float is an ' - 'IEEE 754 double-\n' - ' precision number, in order that "-1e-100 % 1e100" ' - 'have the same\n' - ' sign as "1e100", the computed result is "-1e-100 + ' - '1e100", which\n' - ' is numerically exactly equal to "1e100". The ' - 'function\n' - ' "math.fmod()" returns a result whose sign matches ' - 'the sign of the\n' - ' first argument instead, and so returns "-1e-100" in ' - 'this case.\n' - ' Which approach is more appropriate depends on the ' - 'application.\n' - '\n' - '[2] If x is very close to an exact integer multiple of ' - 'y, it’s\n' - ' possible for "x//y" to be one larger than ' - '"(x-x%y)//y" due to\n' - ' rounding. In such cases, Python returns the latter ' - 'result, in\n' - ' order to preserve that "divmod(x,y)[0] * y + x % y" ' - 'be very close\n' - ' to "x".\n' - '\n' - '[3] The Unicode standard distinguishes between *code ' - 'points* (e.g.\n' - ' U+0041) and *abstract characters* (e.g. “LATIN ' - 'CAPITAL LETTER A”).\n' - ' While most abstract characters in Unicode are only ' - 'represented\n' - ' using one code point, there is a number of abstract ' - 'characters\n' - ' that can in addition be represented using a sequence ' - 'of more than\n' - ' one code point. For example, the abstract character ' - '“LATIN\n' - ' CAPITAL LETTER C WITH CEDILLA” can be represented as ' - 'a single\n' - ' *precomposed character* at code position U+00C7, or ' - 'as a sequence\n' - ' of a *base character* at code position U+0043 (LATIN ' - 'CAPITAL\n' - ' LETTER C), followed by a *combining character* at ' - 'code position\n' - ' U+0327 (COMBINING CEDILLA).\n' - '\n' - ' The comparison operators on strings compare at the ' - 'level of\n' - ' Unicode code points. This may be counter-intuitive ' - 'to humans. For\n' - ' example, ""\\u00C7" == "\\u0043\\u0327"" is "False", ' - 'even though both\n' - ' strings represent the same abstract character “LATIN ' - 'CAPITAL\n' - ' LETTER C WITH CEDILLA”.\n' - '\n' - ' To compare strings at the level of abstract ' - 'characters (that is,\n' - ' in a way intuitive to humans), use ' - '"unicodedata.normalize()".\n' - '\n' - '[4] Due to automatic garbage-collection, free lists, and ' - 'the dynamic\n' - ' nature of descriptors, you may notice seemingly ' - 'unusual behaviour\n' - ' in certain uses of the "is" operator, like those ' - 'involving\n' - ' comparisons between instance methods, or constants. ' - 'Check their\n' - ' documentation for more info.\n' - '\n' - '[5] The power operator "**" binds less tightly than an ' - 'arithmetic or\n' - ' bitwise unary operator on its right, that is, ' - '"2**-1" is "0.5".\n' - '\n' - '[6] The "%" operator is also used for string formatting; ' - 'the same\n' - ' precedence applies.\n', - 'pass': 'The "pass" statement\n' - '********************\n' - '\n' - ' pass_stmt ::= "pass"\n' - '\n' - '"pass" is a null operation — when it is executed, nothing happens. ' - 'It\n' - 'is useful as a placeholder when a statement is required ' - 'syntactically,\n' - 'but no code needs to be executed, for example:\n' - '\n' - ' def f(arg): pass # a function that does nothing (yet)\n' - '\n' - ' class C: pass # a class with no methods (yet)\n', - 'power': 'The power operator\n' - '******************\n' - '\n' - 'The power operator binds more tightly than unary operators on its\n' - 'left; it binds less tightly than unary operators on its right. ' - 'The\n' - 'syntax is:\n' - '\n' - ' power ::= (await_expr | primary) ["**" u_expr]\n' - '\n' - 'Thus, in an unparenthesized sequence of power and unary operators, ' - 'the\n' - 'operators are evaluated from right to left (this does not ' - 'constrain\n' - 'the evaluation order for the operands): "-1**2" results in "-1".\n' - '\n' - 'The power operator has the same semantics as the built-in "pow()"\n' - 'function, when called with two arguments: it yields its left ' - 'argument\n' - 'raised to the power of its right argument. The numeric arguments ' - 'are\n' - 'first converted to a common type, and the result is of that type.\n' - '\n' - 'For int operands, the result has the same type as the operands ' - 'unless\n' - 'the second argument is negative; in that case, all arguments are\n' - 'converted to float and a float result is delivered. For example,\n' - '"10**2" returns "100", but "10**-2" returns "0.01".\n' - '\n' - 'Raising "0.0" to a negative power results in a ' - '"ZeroDivisionError".\n' - 'Raising a negative number to a fractional power results in a ' - '"complex"\n' - 'number. (In earlier versions it raised a "ValueError".)\n' - '\n' - 'This operation can be customized using the special "__pow__()" and\n' - '"__rpow__()" methods.\n', - 'raise': 'The "raise" statement\n' - '*********************\n' - '\n' - ' raise_stmt ::= "raise" [expression ["from" expression]]\n' - '\n' - 'If no expressions are present, "raise" re-raises the exception that ' - 'is\n' - 'currently being handled, which is also known as the *active\n' - 'exception*. If there isn’t currently an active exception, a\n' - '"RuntimeError" exception is raised indicating that this is an ' - 'error.\n' - '\n' - 'Otherwise, "raise" evaluates the first expression as the exception\n' - 'object. It must be either a subclass or an instance of\n' - '"BaseException". If it is a class, the exception instance will be\n' - 'obtained when needed by instantiating the class with no arguments.\n' - '\n' - 'The *type* of the exception is the exception instance’s class, the\n' - '*value* is the instance itself.\n' - '\n' - 'A traceback object is normally created automatically when an ' - 'exception\n' - 'is raised and attached to it as the "__traceback__" attribute. You ' - 'can\n' - 'create an exception and set your own traceback in one step using ' - 'the\n' - '"with_traceback()" exception method (which returns the same ' - 'exception\n' - 'instance, with its traceback set to its argument), like so:\n' - '\n' - ' raise Exception("foo occurred").with_traceback(tracebackobj)\n' - '\n' - 'The "from" clause is used for exception chaining: if given, the ' - 'second\n' - '*expression* must be another exception class or instance. If the\n' - 'second expression is an exception instance, it will be attached to ' - 'the\n' - 'raised exception as the "__cause__" attribute (which is writable). ' - 'If\n' - 'the expression is an exception class, the class will be ' - 'instantiated\n' - 'and the resulting exception instance will be attached to the ' - 'raised\n' - 'exception as the "__cause__" attribute. If the raised exception is ' - 'not\n' - 'handled, both exceptions will be printed:\n' - '\n' - ' >>> try:\n' - ' ... print(1 / 0)\n' - ' ... except Exception as exc:\n' - ' ... raise RuntimeError("Something bad happened") from exc\n' - ' ...\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 2, in <module>\n' - ' print(1 / 0)\n' - ' ~~^~~\n' - ' ZeroDivisionError: division by zero\n' - '\n' - ' The above exception was the direct cause of the following ' - 'exception:\n' - '\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 4, in <module>\n' - ' raise RuntimeError("Something bad happened") from exc\n' - ' RuntimeError: Something bad happened\n' - '\n' - 'A similar mechanism works implicitly if a new exception is raised ' - 'when\n' - 'an exception is already being handled. An exception may be ' - 'handled\n' - 'when an "except" or "finally" clause, or a "with" statement, is ' - 'used.\n' - 'The previous exception is then attached as the new exception’s\n' - '"__context__" attribute:\n' - '\n' - ' >>> try:\n' - ' ... print(1 / 0)\n' - ' ... except:\n' - ' ... raise RuntimeError("Something bad happened")\n' - ' ...\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 2, in <module>\n' - ' print(1 / 0)\n' - ' ~~^~~\n' - ' ZeroDivisionError: division by zero\n' - '\n' - ' During handling of the above exception, another exception ' - 'occurred:\n' - '\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 4, in <module>\n' - ' raise RuntimeError("Something bad happened")\n' - ' RuntimeError: Something bad happened\n' - '\n' - 'Exception chaining can be explicitly suppressed by specifying ' - '"None"\n' - 'in the "from" clause:\n' - '\n' - ' >>> try:\n' - ' ... print(1 / 0)\n' - ' ... except:\n' - ' ... raise RuntimeError("Something bad happened") from None\n' - ' ...\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 4, in <module>\n' - ' RuntimeError: Something bad happened\n' - '\n' - 'Additional information on exceptions can be found in section\n' - 'Exceptions, and information about handling exceptions is in ' - 'section\n' - 'The try statement.\n' - '\n' - 'Changed in version 3.3: "None" is now permitted as "Y" in "raise X\n' - 'from Y".Added the "__suppress_context__" attribute to suppress\n' - 'automatic display of the exception context.\n' - '\n' - 'Changed in version 3.11: If the traceback of the active exception ' - 'is\n' - 'modified in an "except" clause, a subsequent "raise" statement re-\n' - 'raises the exception with the modified traceback. Previously, the\n' - 'exception was re-raised with the traceback it had when it was ' - 'caught.\n', - 'return': 'The "return" statement\n' - '**********************\n' - '\n' - ' return_stmt ::= "return" [expression_list]\n' - '\n' - '"return" may only occur syntactically nested in a function ' - 'definition,\n' - 'not within a nested class definition.\n' - '\n' - 'If an expression list is present, it is evaluated, else "None" is\n' - 'substituted.\n' - '\n' - '"return" leaves the current function call with the expression list ' - '(or\n' - '"None") as return value.\n' - '\n' - 'When "return" passes control out of a "try" statement with a ' - '"finally"\n' - 'clause, that "finally" clause is executed before really leaving ' - 'the\n' - 'function.\n' - '\n' - 'In a generator function, the "return" statement indicates that ' - 'the\n' - 'generator is done and will cause "StopIteration" to be raised. ' - 'The\n' - 'returned value (if any) is used as an argument to construct\n' - '"StopIteration" and becomes the "StopIteration.value" attribute.\n' - '\n' - 'In an asynchronous generator function, an empty "return" ' - 'statement\n' - 'indicates that the asynchronous generator is done and will cause\n' - '"StopAsyncIteration" to be raised. A non-empty "return" statement ' - 'is\n' - 'a syntax error in an asynchronous generator function.\n', - 'sequence-types': 'Emulating container types\n' - '*************************\n' - '\n' - 'The following methods can be defined to implement ' - 'container objects.\n' - 'None of them are provided by the "object" class itself. ' - 'Containers\n' - 'usually are *sequences* (such as "lists" or "tuples") or ' - '*mappings*\n' - '(like *dictionaries*), but can represent other containers ' - 'as well.\n' - 'The first set of methods is used either to emulate a ' - 'sequence or to\n' - 'emulate a mapping; the difference is that for a sequence, ' - 'the\n' - 'allowable keys should be the integers *k* for which "0 <= ' - 'k < N" where\n' - '*N* is the length of the sequence, or "slice" objects, ' - 'which define a\n' - 'range of items. It is also recommended that mappings ' - 'provide the\n' - 'methods "keys()", "values()", "items()", "get()", ' - '"clear()",\n' - '"setdefault()", "pop()", "popitem()", "copy()", and ' - '"update()"\n' - 'behaving similar to those for Python’s standard ' - '"dictionary" objects.\n' - 'The "collections.abc" module provides a "MutableMapping" ' - '*abstract\n' - 'base class* to help create those methods from a base set ' - 'of\n' - '"__getitem__()", "__setitem__()", "__delitem__()", and ' - '"keys()".\n' - 'Mutable sequences should provide methods "append()", ' - '"count()",\n' - '"index()", "extend()", "insert()", "pop()", "remove()", ' - '"reverse()"\n' - 'and "sort()", like Python standard "list" objects. ' - 'Finally, sequence\n' - 'types should implement addition (meaning concatenation) ' - 'and\n' - 'multiplication (meaning repetition) by defining the ' - 'methods\n' - '"__add__()", "__radd__()", "__iadd__()", "__mul__()", ' - '"__rmul__()" and\n' - '"__imul__()" described below; they should not define other ' - 'numerical\n' - 'operators. It is recommended that both mappings and ' - 'sequences\n' - 'implement the "__contains__()" method to allow efficient ' - 'use of the\n' - '"in" operator; for mappings, "in" should search the ' - 'mapping’s keys;\n' - 'for sequences, it should search through the values. It is ' - 'further\n' - 'recommended that both mappings and sequences implement ' - 'the\n' - '"__iter__()" method to allow efficient iteration through ' - 'the\n' - 'container; for mappings, "__iter__()" should iterate ' - 'through the\n' - 'object’s keys; for sequences, it should iterate through ' - 'the values.\n' - '\n' - 'object.__len__(self)\n' - '\n' - ' Called to implement the built-in function "len()". ' - 'Should return\n' - ' the length of the object, an integer ">=" 0. Also, an ' - 'object that\n' - ' doesn’t define a "__bool__()" method and whose ' - '"__len__()" method\n' - ' returns zero is considered to be false in a Boolean ' - 'context.\n' - '\n' - ' **CPython implementation detail:** In CPython, the ' - 'length is\n' - ' required to be at most "sys.maxsize". If the length is ' - 'larger than\n' - ' "sys.maxsize" some features (such as "len()") may ' - 'raise\n' - ' "OverflowError". To prevent raising "OverflowError" by ' - 'truth value\n' - ' testing, an object must define a "__bool__()" method.\n' - '\n' - 'object.__length_hint__(self)\n' - '\n' - ' Called to implement "operator.length_hint()". Should ' - 'return an\n' - ' estimated length for the object (which may be greater ' - 'or less than\n' - ' the actual length). The length must be an integer ">=" ' - '0. The\n' - ' return value may also be "NotImplemented", which is ' - 'treated the\n' - ' same as if the "__length_hint__" method didn’t exist at ' - 'all. This\n' - ' method is purely an optimization and is never required ' - 'for\n' - ' correctness.\n' - '\n' - ' Added in version 3.4.\n' - '\n' - 'Note:\n' - '\n' - ' Slicing is done exclusively with the following three ' - 'methods. A\n' - ' call like\n' - '\n' - ' a[1:2] = b\n' - '\n' - ' is translated to\n' - '\n' - ' a[slice(1, 2, None)] = b\n' - '\n' - ' and so forth. Missing slice items are always filled in ' - 'with "None".\n' - '\n' - 'object.__getitem__(self, key)\n' - '\n' - ' Called to implement evaluation of "self[key]". For ' - '*sequence*\n' - ' types, the accepted keys should be integers. ' - 'Optionally, they may\n' - ' support "slice" objects as well. Negative index ' - 'support is also\n' - ' optional. If *key* is of an inappropriate type, ' - '"TypeError" may be\n' - ' raised; if *key* is a value outside the set of indexes ' - 'for the\n' - ' sequence (after any special interpretation of negative ' - 'values),\n' - ' "IndexError" should be raised. For *mapping* types, if ' - '*key* is\n' - ' missing (not in the container), "KeyError" should be ' - 'raised.\n' - '\n' - ' Note:\n' - '\n' - ' "for" loops expect that an "IndexError" will be ' - 'raised for\n' - ' illegal indexes to allow proper detection of the end ' - 'of the\n' - ' sequence.\n' - '\n' - ' Note:\n' - '\n' - ' When subscripting a *class*, the special class ' - 'method\n' - ' "__class_getitem__()" may be called instead of ' - '"__getitem__()".\n' - ' See __class_getitem__ versus __getitem__ for more ' - 'details.\n' - '\n' - 'object.__setitem__(self, key, value)\n' - '\n' - ' Called to implement assignment to "self[key]". Same ' - 'note as for\n' - ' "__getitem__()". This should only be implemented for ' - 'mappings if\n' - ' the objects support changes to the values for keys, or ' - 'if new keys\n' - ' can be added, or for sequences if elements can be ' - 'replaced. The\n' - ' same exceptions should be raised for improper *key* ' - 'values as for\n' - ' the "__getitem__()" method.\n' - '\n' - 'object.__delitem__(self, key)\n' - '\n' - ' Called to implement deletion of "self[key]". Same note ' - 'as for\n' - ' "__getitem__()". This should only be implemented for ' - 'mappings if\n' - ' the objects support removal of keys, or for sequences ' - 'if elements\n' - ' can be removed from the sequence. The same exceptions ' - 'should be\n' - ' raised for improper *key* values as for the ' - '"__getitem__()" method.\n' - '\n' - 'object.__missing__(self, key)\n' - '\n' - ' Called by "dict"."__getitem__()" to implement ' - '"self[key]" for dict\n' - ' subclasses when key is not in the dictionary.\n' - '\n' - 'object.__iter__(self)\n' - '\n' - ' This method is called when an *iterator* is required ' - 'for a\n' - ' container. This method should return a new iterator ' - 'object that can\n' - ' iterate over all the objects in the container. For ' - 'mappings, it\n' - ' should iterate over the keys of the container.\n' - '\n' - 'object.__reversed__(self)\n' - '\n' - ' Called (if present) by the "reversed()" built-in to ' - 'implement\n' - ' reverse iteration. It should return a new iterator ' - 'object that\n' - ' iterates over all the objects in the container in ' - 'reverse order.\n' - '\n' - ' If the "__reversed__()" method is not provided, the ' - '"reversed()"\n' - ' built-in will fall back to using the sequence protocol ' - '("__len__()"\n' - ' and "__getitem__()"). Objects that support the ' - 'sequence protocol\n' - ' should only provide "__reversed__()" if they can ' - 'provide an\n' - ' implementation that is more efficient than the one ' - 'provided by\n' - ' "reversed()".\n' - '\n' - 'The membership test operators ("in" and "not in") are ' - 'normally\n' - 'implemented as an iteration through a container. However, ' - 'container\n' - 'objects can supply the following special method with a ' - 'more efficient\n' - 'implementation, which also does not require the object be ' - 'iterable.\n' - '\n' - 'object.__contains__(self, item)\n' - '\n' - ' Called to implement membership test operators. Should ' - 'return true\n' - ' if *item* is in *self*, false otherwise. For mapping ' - 'objects, this\n' - ' should consider the keys of the mapping rather than the ' - 'values or\n' - ' the key-item pairs.\n' - '\n' - ' For objects that don’t define "__contains__()", the ' - 'membership test\n' - ' first tries iteration via "__iter__()", then the old ' - 'sequence\n' - ' iteration protocol via "__getitem__()", see this ' - 'section in the\n' - ' language reference.\n', - 'shifting': 'Shifting operations\n' - '*******************\n' - '\n' - 'The shifting operations have lower priority than the arithmetic\n' - 'operations:\n' - '\n' - ' shift_expr ::= a_expr | shift_expr ("<<" | ">>") a_expr\n' - '\n' - 'These operators accept integers as arguments. They shift the ' - 'first\n' - 'argument to the left or right by the number of bits given by ' - 'the\n' - 'second argument.\n' - '\n' - 'The left shift operation can be customized using the special\n' - '"__lshift__()" and "__rlshift__()" methods. The right shift ' - 'operation\n' - 'can be customized using the special "__rshift__()" and ' - '"__rrshift__()"\n' - 'methods.\n' - '\n' - 'A right shift by *n* bits is defined as floor division by ' - '"pow(2,n)".\n' - 'A left shift by *n* bits is defined as multiplication with ' - '"pow(2,n)".\n', - 'slicings': 'Slicings\n' - '********\n' - '\n' - 'A slicing selects a range of items in a sequence object (e.g., ' - 'a\n' - 'string, tuple or list). Slicings may be used as expressions or ' - 'as\n' - 'targets in assignment or "del" statements. The syntax for a ' - 'slicing:\n' - '\n' - ' slicing ::= primary "[" slice_list "]"\n' - ' slice_list ::= slice_item ("," slice_item)* [","]\n' - ' slice_item ::= expression | proper_slice\n' - ' proper_slice ::= [lower_bound] ":" [upper_bound] [ ":" ' - '[stride] ]\n' - ' lower_bound ::= expression\n' - ' upper_bound ::= expression\n' - ' stride ::= expression\n' - '\n' - 'There is ambiguity in the formal syntax here: anything that ' - 'looks like\n' - 'an expression list also looks like a slice list, so any ' - 'subscription\n' - 'can be interpreted as a slicing. Rather than further ' - 'complicating the\n' - 'syntax, this is disambiguated by defining that in this case the\n' - 'interpretation as a subscription takes priority over the\n' - 'interpretation as a slicing (this is the case if the slice list\n' - 'contains no proper slice).\n' - '\n' - 'The semantics for a slicing are as follows. The primary is ' - 'indexed\n' - '(using the same "__getitem__()" method as normal subscription) ' - 'with a\n' - 'key that is constructed from the slice list, as follows. If the ' - 'slice\n' - 'list contains at least one comma, the key is a tuple containing ' - 'the\n' - 'conversion of the slice items; otherwise, the conversion of the ' - 'lone\n' - 'slice item is the key. The conversion of a slice item that is ' - 'an\n' - 'expression is that expression. The conversion of a proper slice ' - 'is a\n' - 'slice object (see section The standard type hierarchy) whose ' - '"start",\n' - '"stop" and "step" attributes are the values of the expressions ' - 'given\n' - 'as lower bound, upper bound and stride, respectively, ' - 'substituting\n' - '"None" for missing expressions.\n', - 'specialattrs': 'Special Attributes\n' - '******************\n' - '\n' - 'The implementation adds a few special read-only attributes ' - 'to several\n' - 'object types, where they are relevant. Some of these are ' - 'not reported\n' - 'by the "dir()" built-in function.\n' - '\n' - 'definition.__name__\n' - '\n' - ' The name of the class, function, method, descriptor, or ' - 'generator\n' - ' instance.\n' - '\n' - 'definition.__qualname__\n' - '\n' - ' The *qualified name* of the class, function, method, ' - 'descriptor, or\n' - ' generator instance.\n' - '\n' - ' Added in version 3.3.\n' - '\n' - 'definition.__module__\n' - '\n' - ' The name of the module in which a class or function was ' - 'defined.\n' - '\n' - 'definition.__doc__\n' - '\n' - ' The documentation string of a class or function, or ' - '"None" if\n' - ' undefined.\n' - '\n' - 'definition.__type_params__\n' - '\n' - ' The type parameters of generic classes, functions, and ' - 'type\n' - ' aliases. For classes and functions that are not generic, ' - 'this will\n' - ' be an empty tuple.\n' - '\n' - ' Added in version 3.12.\n', - 'specialnames': 'Special method names\n' - '********************\n' - '\n' - 'A class can implement certain operations that are invoked by ' - 'special\n' - 'syntax (such as arithmetic operations or subscripting and ' - 'slicing) by\n' - 'defining methods with special names. This is Python’s ' - 'approach to\n' - '*operator overloading*, allowing classes to define their own ' - 'behavior\n' - 'with respect to language operators. For instance, if a ' - 'class defines\n' - 'a method named "__getitem__()", and "x" is an instance of ' - 'this class,\n' - 'then "x[i]" is roughly equivalent to "type(x).__getitem__(x, ' - 'i)".\n' - 'Except where mentioned, attempts to execute an operation ' - 'raise an\n' - 'exception when no appropriate method is defined (typically\n' - '"AttributeError" or "TypeError").\n' - '\n' - 'Setting a special method to "None" indicates that the ' - 'corresponding\n' - 'operation is not available. For example, if a class sets ' - '"__iter__()"\n' - 'to "None", the class is not iterable, so calling "iter()" on ' - 'its\n' - 'instances will raise a "TypeError" (without falling back to\n' - '"__getitem__()"). [2]\n' - '\n' - 'When implementing a class that emulates any built-in type, ' - 'it is\n' - 'important that the emulation only be implemented to the ' - 'degree that it\n' - 'makes sense for the object being modelled. For example, ' - 'some\n' - 'sequences may work well with retrieval of individual ' - 'elements, but\n' - 'extracting a slice may not make sense. (One example of this ' - 'is the\n' - '"NodeList" interface in the W3C’s Document Object Model.)\n' - '\n' - '\n' - 'Basic customization\n' - '===================\n' - '\n' - 'object.__new__(cls[, ...])\n' - '\n' - ' Called to create a new instance of class *cls*. ' - '"__new__()" is a\n' - ' static method (special-cased so you need not declare it ' - 'as such)\n' - ' that takes the class of which an instance was requested ' - 'as its\n' - ' first argument. The remaining arguments are those passed ' - 'to the\n' - ' object constructor expression (the call to the class). ' - 'The return\n' - ' value of "__new__()" should be the new object instance ' - '(usually an\n' - ' instance of *cls*).\n' - '\n' - ' Typical implementations create a new instance of the ' - 'class by\n' - ' invoking the superclass’s "__new__()" method using\n' - ' "super().__new__(cls[, ...])" with appropriate arguments ' - 'and then\n' - ' modifying the newly created instance as necessary before ' - 'returning\n' - ' it.\n' - '\n' - ' If "__new__()" is invoked during object construction and ' - 'it returns\n' - ' an instance of *cls*, then the new instance’s ' - '"__init__()" method\n' - ' will be invoked like "__init__(self[, ...])", where ' - '*self* is the\n' - ' new instance and the remaining arguments are the same as ' - 'were\n' - ' passed to the object constructor.\n' - '\n' - ' If "__new__()" does not return an instance of *cls*, then ' - 'the new\n' - ' instance’s "__init__()" method will not be invoked.\n' - '\n' - ' "__new__()" is intended mainly to allow subclasses of ' - 'immutable\n' - ' types (like int, str, or tuple) to customize instance ' - 'creation. It\n' - ' is also commonly overridden in custom metaclasses in ' - 'order to\n' - ' customize class creation.\n' - '\n' - 'object.__init__(self[, ...])\n' - '\n' - ' Called after the instance has been created (by ' - '"__new__()"), but\n' - ' before it is returned to the caller. The arguments are ' - 'those\n' - ' passed to the class constructor expression. If a base ' - 'class has an\n' - ' "__init__()" method, the derived class’s "__init__()" ' - 'method, if\n' - ' any, must explicitly call it to ensure proper ' - 'initialization of the\n' - ' base class part of the instance; for example:\n' - ' "super().__init__([args...])".\n' - '\n' - ' Because "__new__()" and "__init__()" work together in ' - 'constructing\n' - ' objects ("__new__()" to create it, and "__init__()" to ' - 'customize\n' - ' it), no non-"None" value may be returned by "__init__()"; ' - 'doing so\n' - ' will cause a "TypeError" to be raised at runtime.\n' - '\n' - 'object.__del__(self)\n' - '\n' - ' Called when the instance is about to be destroyed. This ' - 'is also\n' - ' called a finalizer or (improperly) a destructor. If a ' - 'base class\n' - ' has a "__del__()" method, the derived class’s "__del__()" ' - 'method,\n' - ' if any, must explicitly call it to ensure proper deletion ' - 'of the\n' - ' base class part of the instance.\n' - '\n' - ' It is possible (though not recommended!) for the ' - '"__del__()" method\n' - ' to postpone destruction of the instance by creating a new ' - 'reference\n' - ' to it. This is called object *resurrection*. It is\n' - ' implementation-dependent whether "__del__()" is called a ' - 'second\n' - ' time when a resurrected object is about to be destroyed; ' - 'the\n' - ' current *CPython* implementation only calls it once.\n' - '\n' - ' It is not guaranteed that "__del__()" methods are called ' - 'for\n' - ' objects that still exist when the interpreter exits.\n' - ' "weakref.finalize" provides a straightforward way to ' - 'register a\n' - ' cleanup function to be called when an object is garbage ' - 'collected.\n' - '\n' - ' Note:\n' - '\n' - ' "del x" doesn’t directly call "x.__del__()" — the ' - 'former\n' - ' decrements the reference count for "x" by one, and the ' - 'latter is\n' - ' only called when "x"’s reference count reaches zero.\n' - '\n' - ' **CPython implementation detail:** It is possible for a ' - 'reference\n' - ' cycle to prevent the reference count of an object from ' - 'going to\n' - ' zero. In this case, the cycle will be later detected and ' - 'deleted\n' - ' by the *cyclic garbage collector*. A common cause of ' - 'reference\n' - ' cycles is when an exception has been caught in a local ' - 'variable.\n' - ' The frame’s locals then reference the exception, which ' - 'references\n' - ' its own traceback, which references the locals of all ' - 'frames caught\n' - ' in the traceback.\n' - '\n' - ' See also: Documentation for the "gc" module.\n' - '\n' - ' Warning:\n' - '\n' - ' Due to the precarious circumstances under which ' - '"__del__()"\n' - ' methods are invoked, exceptions that occur during their ' - 'execution\n' - ' are ignored, and a warning is printed to "sys.stderr" ' - 'instead.\n' - ' In particular:\n' - '\n' - ' * "__del__()" can be invoked when arbitrary code is ' - 'being\n' - ' executed, including from any arbitrary thread. If ' - '"__del__()"\n' - ' needs to take a lock or invoke any other blocking ' - 'resource, it\n' - ' may deadlock as the resource may already be taken by ' - 'the code\n' - ' that gets interrupted to execute "__del__()".\n' - '\n' - ' * "__del__()" can be executed during interpreter ' - 'shutdown. As a\n' - ' consequence, the global variables it needs to access ' - '(including\n' - ' other modules) may already have been deleted or set ' - 'to "None".\n' - ' Python guarantees that globals whose name begins with ' - 'a single\n' - ' underscore are deleted from their module before other ' - 'globals\n' - ' are deleted; if no other references to such globals ' - 'exist, this\n' - ' may help in assuring that imported modules are still ' - 'available\n' - ' at the time when the "__del__()" method is called.\n' - '\n' - 'object.__repr__(self)\n' - '\n' - ' Called by the "repr()" built-in function to compute the ' - '“official”\n' - ' string representation of an object. If at all possible, ' - 'this\n' - ' should look like a valid Python expression that could be ' - 'used to\n' - ' recreate an object with the same value (given an ' - 'appropriate\n' - ' environment). If this is not possible, a string of the ' - 'form\n' - ' "<...some useful description...>" should be returned. The ' - 'return\n' - ' value must be a string object. If a class defines ' - '"__repr__()" but\n' - ' not "__str__()", then "__repr__()" is also used when an ' - '“informal”\n' - ' string representation of instances of that class is ' - 'required.\n' - '\n' - ' This is typically used for debugging, so it is important ' - 'that the\n' - ' representation is information-rich and unambiguous. A ' - 'default\n' - ' implementation is provided by the "object" class itself.\n' - '\n' - 'object.__str__(self)\n' - '\n' - ' Called by "str(object)", the default "__format__()" ' - 'implementation,\n' - ' and the built-in function "print()", to compute the ' - '“informal” or\n' - ' nicely printable string representation of an object. The ' - 'return\n' - ' value must be a str object.\n' - '\n' - ' This method differs from "object.__repr__()" in that ' - 'there is no\n' - ' expectation that "__str__()" return a valid Python ' - 'expression: a\n' - ' more convenient or concise representation can be used.\n' - '\n' - ' The default implementation defined by the built-in type ' - '"object"\n' - ' calls "object.__repr__()".\n' - '\n' - 'object.__bytes__(self)\n' - '\n' - ' Called by bytes to compute a byte-string representation ' - 'of an\n' - ' object. This should return a "bytes" object. The "object" ' - 'class\n' - ' itself does not provide this method.\n' - '\n' - 'object.__format__(self, format_spec)\n' - '\n' - ' Called by the "format()" built-in function, and by ' - 'extension,\n' - ' evaluation of formatted string literals and the ' - '"str.format()"\n' - ' method, to produce a “formatted” string representation of ' - 'an\n' - ' object. The *format_spec* argument is a string that ' - 'contains a\n' - ' description of the formatting options desired. The ' - 'interpretation\n' - ' of the *format_spec* argument is up to the type ' - 'implementing\n' - ' "__format__()", however most classes will either ' - 'delegate\n' - ' formatting to one of the built-in types, or use a ' - 'similar\n' - ' formatting option syntax.\n' - '\n' - ' See Format Specification Mini-Language for a description ' - 'of the\n' - ' standard formatting syntax.\n' - '\n' - ' The return value must be a string object.\n' - '\n' - ' The default implementation by the "object" class should ' - 'be given an\n' - ' empty *format_spec* string. It delegates to "__str__()".\n' - '\n' - ' Changed in version 3.4: The __format__ method of "object" ' - 'itself\n' - ' raises a "TypeError" if passed any non-empty string.\n' - '\n' - ' Changed in version 3.7: "object.__format__(x, \'\')" is ' - 'now\n' - ' equivalent to "str(x)" rather than "format(str(x), ' - '\'\')".\n' - '\n' - 'object.__lt__(self, other)\n' - 'object.__le__(self, other)\n' - 'object.__eq__(self, other)\n' - 'object.__ne__(self, other)\n' - 'object.__gt__(self, other)\n' - 'object.__ge__(self, other)\n' - '\n' - ' These are the so-called “rich comparison” methods. The\n' - ' correspondence between operator symbols and method names ' - 'is as\n' - ' follows: "x<y" calls "x.__lt__(y)", "x<=y" calls ' - '"x.__le__(y)",\n' - ' "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", ' - '"x>y" calls\n' - ' "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)".\n' - '\n' - ' A rich comparison method may return the singleton ' - '"NotImplemented"\n' - ' if it does not implement the operation for a given pair ' - 'of\n' - ' arguments. By convention, "False" and "True" are returned ' - 'for a\n' - ' successful comparison. However, these methods can return ' - 'any value,\n' - ' so if the comparison operator is used in a Boolean ' - 'context (e.g.,\n' - ' in the condition of an "if" statement), Python will call ' - '"bool()"\n' - ' on the value to determine if the result is true or ' - 'false.\n' - '\n' - ' By default, "object" implements "__eq__()" by using "is", ' - 'returning\n' - ' "NotImplemented" in the case of a false comparison: "True ' - 'if x is y\n' - ' else NotImplemented". For "__ne__()", by default it ' - 'delegates to\n' - ' "__eq__()" and inverts the result unless it is ' - '"NotImplemented".\n' - ' There are no other implied relationships among the ' - 'comparison\n' - ' operators or default implementations; for example, the ' - 'truth of\n' - ' "(x<y or x==y)" does not imply "x<=y". To automatically ' - 'generate\n' - ' ordering operations from a single root operation, see\n' - ' "functools.total_ordering()".\n' - '\n' - ' By default, the "object" class provides implementations ' - 'consistent\n' - ' with Value comparisons: equality compares according to ' - 'object\n' - ' identity, and order comparisons raise "TypeError". Each ' - 'default\n' - ' method may generate these results directly, but may also ' - 'return\n' - ' "NotImplemented".\n' - '\n' - ' See the paragraph on "__hash__()" for some important ' - 'notes on\n' - ' creating *hashable* objects which support custom ' - 'comparison\n' - ' operations and are usable as dictionary keys.\n' - '\n' - ' There are no swapped-argument versions of these methods ' - '(to be used\n' - ' when the left argument does not support the operation but ' - 'the right\n' - ' argument does); rather, "__lt__()" and "__gt__()" are ' - 'each other’s\n' - ' reflection, "__le__()" and "__ge__()" are each other’s ' - 'reflection,\n' - ' and "__eq__()" and "__ne__()" are their own reflection. ' - 'If the\n' - ' operands are of different types, and the right operand’s ' - 'type is a\n' - ' direct or indirect subclass of the left operand’s type, ' - 'the\n' - ' reflected method of the right operand has priority, ' - 'otherwise the\n' - ' left operand’s method has priority. Virtual subclassing ' - 'is not\n' - ' considered.\n' - '\n' - ' When no appropriate method returns any value other than\n' - ' "NotImplemented", the "==" and "!=" operators will fall ' - 'back to\n' - ' "is" and "is not", respectively.\n' - '\n' - 'object.__hash__(self)\n' - '\n' - ' Called by built-in function "hash()" and for operations ' - 'on members\n' - ' of hashed collections including "set", "frozenset", and ' - '"dict".\n' - ' The "__hash__()" method should return an integer. The ' - 'only required\n' - ' property is that objects which compare equal have the ' - 'same hash\n' - ' value; it is advised to mix together the hash values of ' - 'the\n' - ' components of the object that also play a part in ' - 'comparison of\n' - ' objects by packing them into a tuple and hashing the ' - 'tuple.\n' - ' Example:\n' - '\n' - ' def __hash__(self):\n' - ' return hash((self.name, self.nick, self.color))\n' - '\n' - ' Note:\n' - '\n' - ' "hash()" truncates the value returned from an object’s ' - 'custom\n' - ' "__hash__()" method to the size of a "Py_ssize_t". ' - 'This is\n' - ' typically 8 bytes on 64-bit builds and 4 bytes on ' - '32-bit builds.\n' - ' If an object’s "__hash__()" must interoperate on ' - 'builds of\n' - ' different bit sizes, be sure to check the width on all ' - 'supported\n' - ' builds. An easy way to do this is with "python -c ' - '"import sys;\n' - ' print(sys.hash_info.width)"".\n' - '\n' - ' If a class does not define an "__eq__()" method it should ' - 'not\n' - ' define a "__hash__()" operation either; if it defines ' - '"__eq__()"\n' - ' but not "__hash__()", its instances will not be usable as ' - 'items in\n' - ' hashable collections. If a class defines mutable objects ' - 'and\n' - ' implements an "__eq__()" method, it should not implement\n' - ' "__hash__()", since the implementation of *hashable* ' - 'collections\n' - ' requires that a key’s hash value is immutable (if the ' - 'object’s hash\n' - ' value changes, it will be in the wrong hash bucket).\n' - '\n' - ' User-defined classes have "__eq__()" and "__hash__()" ' - 'methods by\n' - ' default (inherited from the "object" class); with them, ' - 'all objects\n' - ' compare unequal (except with themselves) and ' - '"x.__hash__()" returns\n' - ' an appropriate value such that "x == y" implies both that ' - '"x is y"\n' - ' and "hash(x) == hash(y)".\n' - '\n' - ' A class that overrides "__eq__()" and does not define ' - '"__hash__()"\n' - ' will have its "__hash__()" implicitly set to "None". ' - 'When the\n' - ' "__hash__()" method of a class is "None", instances of ' - 'the class\n' - ' will raise an appropriate "TypeError" when a program ' - 'attempts to\n' - ' retrieve their hash value, and will also be correctly ' - 'identified as\n' - ' unhashable when checking "isinstance(obj,\n' - ' collections.abc.Hashable)".\n' - '\n' - ' If a class that overrides "__eq__()" needs to retain the\n' - ' implementation of "__hash__()" from a parent class, the ' - 'interpreter\n' - ' must be told this explicitly by setting "__hash__ =\n' - ' <ParentClass>.__hash__".\n' - '\n' - ' If a class that does not override "__eq__()" wishes to ' - 'suppress\n' - ' hash support, it should include "__hash__ = None" in the ' - 'class\n' - ' definition. A class which defines its own "__hash__()" ' - 'that\n' - ' explicitly raises a "TypeError" would be incorrectly ' - 'identified as\n' - ' hashable by an "isinstance(obj, ' - 'collections.abc.Hashable)" call.\n' - '\n' - ' Note:\n' - '\n' - ' By default, the "__hash__()" values of str and bytes ' - 'objects are\n' - ' “salted” with an unpredictable random value. Although ' - 'they\n' - ' remain constant within an individual Python process, ' - 'they are not\n' - ' predictable between repeated invocations of Python.This ' - 'is\n' - ' intended to provide protection against a ' - 'denial-of-service caused\n' - ' by carefully chosen inputs that exploit the worst case\n' - ' performance of a dict insertion, *O*(*n*^2) ' - 'complexity. See\n' - ' http://ocert.org/advisories/ocert-2011-003.html for\n' - ' details.Changing hash values affects the iteration ' - 'order of sets.\n' - ' Python has never made guarantees about this ordering ' - '(and it\n' - ' typically varies between 32-bit and 64-bit builds).See ' - 'also\n' - ' "PYTHONHASHSEED".\n' - '\n' - ' Changed in version 3.3: Hash randomization is enabled by ' - 'default.\n' - '\n' - 'object.__bool__(self)\n' - '\n' - ' Called to implement truth value testing and the built-in ' - 'operation\n' - ' "bool()"; should return "False" or "True". When this ' - 'method is not\n' - ' defined, "__len__()" is called, if it is defined, and the ' - 'object is\n' - ' considered true if its result is nonzero. If a class ' - 'defines\n' - ' neither "__len__()" nor "__bool__()" (which is true of ' - 'the "object"\n' - ' class itself), all its instances are considered true.\n' - '\n' - '\n' - 'Customizing attribute access\n' - '============================\n' - '\n' - 'The following methods can be defined to customize the ' - 'meaning of\n' - 'attribute access (use of, assignment to, or deletion of ' - '"x.name") for\n' - 'class instances.\n' - '\n' - 'object.__getattr__(self, name)\n' - '\n' - ' Called when the default attribute access fails with an\n' - ' "AttributeError" (either "__getattribute__()" raises an\n' - ' "AttributeError" because *name* is not an instance ' - 'attribute or an\n' - ' attribute in the class tree for "self"; or "__get__()" of ' - 'a *name*\n' - ' property raises "AttributeError"). This method should ' - 'either\n' - ' return the (computed) attribute value or raise an ' - '"AttributeError"\n' - ' exception. The "object" class itself does not provide ' - 'this method.\n' - '\n' - ' Note that if the attribute is found through the normal ' - 'mechanism,\n' - ' "__getattr__()" is not called. (This is an intentional ' - 'asymmetry\n' - ' between "__getattr__()" and "__setattr__()".) This is ' - 'done both for\n' - ' efficiency reasons and because otherwise "__getattr__()" ' - 'would have\n' - ' no way to access other attributes of the instance. Note ' - 'that at\n' - ' least for instance variables, you can take total control ' - 'by not\n' - ' inserting any values in the instance attribute dictionary ' - '(but\n' - ' instead inserting them in another object). See the\n' - ' "__getattribute__()" method below for a way to actually ' - 'get total\n' - ' control over attribute access.\n' - '\n' - 'object.__getattribute__(self, name)\n' - '\n' - ' Called unconditionally to implement attribute accesses ' - 'for\n' - ' instances of the class. If the class also defines ' - '"__getattr__()",\n' - ' the latter will not be called unless "__getattribute__()" ' - 'either\n' - ' calls it explicitly or raises an "AttributeError". This ' - 'method\n' - ' should return the (computed) attribute value or raise an\n' - ' "AttributeError" exception. In order to avoid infinite ' - 'recursion in\n' - ' this method, its implementation should always call the ' - 'base class\n' - ' method with the same name to access any attributes it ' - 'needs, for\n' - ' example, "object.__getattribute__(self, name)".\n' - '\n' - ' Note:\n' - '\n' - ' This method may still be bypassed when looking up ' - 'special methods\n' - ' as the result of implicit invocation via language ' - 'syntax or\n' - ' built-in functions. See Special method lookup.\n' - '\n' - ' For certain sensitive attribute accesses, raises an ' - 'auditing event\n' - ' "object.__getattr__" with arguments "obj" and "name".\n' - '\n' - 'object.__setattr__(self, name, value)\n' - '\n' - ' Called when an attribute assignment is attempted. This ' - 'is called\n' - ' instead of the normal mechanism (i.e. store the value in ' - 'the\n' - ' instance dictionary). *name* is the attribute name, ' - '*value* is the\n' - ' value to be assigned to it.\n' - '\n' - ' If "__setattr__()" wants to assign to an instance ' - 'attribute, it\n' - ' should call the base class method with the same name, for ' - 'example,\n' - ' "object.__setattr__(self, name, value)".\n' - '\n' - ' For certain sensitive attribute assignments, raises an ' - 'auditing\n' - ' event "object.__setattr__" with arguments "obj", "name", ' - '"value".\n' - '\n' - 'object.__delattr__(self, name)\n' - '\n' - ' Like "__setattr__()" but for attribute deletion instead ' - 'of\n' - ' assignment. This should only be implemented if "del ' - 'obj.name" is\n' - ' meaningful for the object.\n' - '\n' - ' For certain sensitive attribute deletions, raises an ' - 'auditing event\n' - ' "object.__delattr__" with arguments "obj" and "name".\n' - '\n' - 'object.__dir__(self)\n' - '\n' - ' Called when "dir()" is called on the object. An iterable ' - 'must be\n' - ' returned. "dir()" converts the returned iterable to a ' - 'list and\n' - ' sorts it.\n' - '\n' - '\n' - 'Customizing module attribute access\n' - '-----------------------------------\n' - '\n' - 'Special names "__getattr__" and "__dir__" can be also used ' - 'to\n' - 'customize access to module attributes. The "__getattr__" ' - 'function at\n' - 'the module level should accept one argument which is the ' - 'name of an\n' - 'attribute and return the computed value or raise an ' - '"AttributeError".\n' - 'If an attribute is not found on a module object through the ' - 'normal\n' - 'lookup, i.e. "object.__getattribute__()", then "__getattr__" ' - 'is\n' - 'searched in the module "__dict__" before raising an ' - '"AttributeError".\n' - 'If found, it is called with the attribute name and the ' - 'result is\n' - 'returned.\n' - '\n' - 'The "__dir__" function should accept no arguments, and ' - 'return an\n' - 'iterable of strings that represents the names accessible on ' - 'module. If\n' - 'present, this function overrides the standard "dir()" search ' - 'on a\n' - 'module.\n' - '\n' - 'For a more fine grained customization of the module behavior ' - '(setting\n' - 'attributes, properties, etc.), one can set the "__class__" ' - 'attribute\n' - 'of a module object to a subclass of "types.ModuleType". For ' - 'example:\n' - '\n' - ' import sys\n' - ' from types import ModuleType\n' - '\n' - ' class VerboseModule(ModuleType):\n' - ' def __repr__(self):\n' - " return f'Verbose {self.__name__}'\n" - '\n' - ' def __setattr__(self, attr, value):\n' - " print(f'Setting {attr}...')\n" - ' super().__setattr__(attr, value)\n' - '\n' - ' sys.modules[__name__].__class__ = VerboseModule\n' - '\n' - 'Note:\n' - '\n' - ' Defining module "__getattr__" and setting module ' - '"__class__" only\n' - ' affect lookups made using the attribute access syntax – ' - 'directly\n' - ' accessing the module globals (whether by code within the ' - 'module, or\n' - ' via a reference to the module’s globals dictionary) is ' - 'unaffected.\n' - '\n' - 'Changed in version 3.5: "__class__" module attribute is now ' - 'writable.\n' - '\n' - 'Added in version 3.7: "__getattr__" and "__dir__" module ' - 'attributes.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 562** - Module __getattr__ and __dir__\n' - ' Describes the "__getattr__" and "__dir__" functions on ' - 'modules.\n' - '\n' - '\n' - 'Implementing Descriptors\n' - '------------------------\n' - '\n' - 'The following methods only apply when an instance of the ' - 'class\n' - 'containing the method (a so-called *descriptor* class) ' - 'appears in an\n' - '*owner* class (the descriptor must be in either the owner’s ' - 'class\n' - 'dictionary or in the class dictionary for one of its ' - 'parents). In the\n' - 'examples below, “the attribute” refers to the attribute ' - 'whose name is\n' - 'the key of the property in the owner class’ "__dict__". The ' - '"object"\n' - 'class itself does not implement any of these protocols.\n' - '\n' - 'object.__get__(self, instance, owner=None)\n' - '\n' - ' Called to get the attribute of the owner class (class ' - 'attribute\n' - ' access) or of an instance of that class (instance ' - 'attribute\n' - ' access). The optional *owner* argument is the owner ' - 'class, while\n' - ' *instance* is the instance that the attribute was ' - 'accessed through,\n' - ' or "None" when the attribute is accessed through the ' - '*owner*.\n' - '\n' - ' This method should return the computed attribute value or ' - 'raise an\n' - ' "AttributeError" exception.\n' - '\n' - ' **PEP 252** specifies that "__get__()" is callable with ' - 'one or two\n' - ' arguments. Python’s own built-in descriptors support ' - 'this\n' - ' specification; however, it is likely that some ' - 'third-party tools\n' - ' have descriptors that require both arguments. Python’s ' - 'own\n' - ' "__getattribute__()" implementation always passes in both ' - 'arguments\n' - ' whether they are required or not.\n' - '\n' - 'object.__set__(self, instance, value)\n' - '\n' - ' Called to set the attribute on an instance *instance* of ' - 'the owner\n' - ' class to a new value, *value*.\n' - '\n' - ' Note, adding "__set__()" or "__delete__()" changes the ' - 'kind of\n' - ' descriptor to a “data descriptor”. See Invoking ' - 'Descriptors for\n' - ' more details.\n' - '\n' - 'object.__delete__(self, instance)\n' - '\n' - ' Called to delete the attribute on an instance *instance* ' - 'of the\n' - ' owner class.\n' - '\n' - 'Instances of descriptors may also have the "__objclass__" ' - 'attribute\n' - 'present:\n' - '\n' - 'object.__objclass__\n' - '\n' - ' The attribute "__objclass__" is interpreted by the ' - '"inspect" module\n' - ' as specifying the class where this object was defined ' - '(setting this\n' - ' appropriately can assist in runtime introspection of ' - 'dynamic class\n' - ' attributes). For callables, it may indicate that an ' - 'instance of the\n' - ' given type (or a subclass) is expected or required as the ' - 'first\n' - ' positional argument (for example, CPython sets this ' - 'attribute for\n' - ' unbound methods that are implemented in C).\n' - '\n' - '\n' - 'Invoking Descriptors\n' - '--------------------\n' - '\n' - 'In general, a descriptor is an object attribute with ' - '“binding\n' - 'behavior”, one whose attribute access has been overridden by ' - 'methods\n' - 'in the descriptor protocol: "__get__()", "__set__()", and\n' - '"__delete__()". If any of those methods are defined for an ' - 'object, it\n' - 'is said to be a descriptor.\n' - '\n' - 'The default behavior for attribute access is to get, set, or ' - 'delete\n' - 'the attribute from an object’s dictionary. For instance, ' - '"a.x" has a\n' - 'lookup chain starting with "a.__dict__[\'x\']", then\n' - '"type(a).__dict__[\'x\']", and continuing through the base ' - 'classes of\n' - '"type(a)" excluding metaclasses.\n' - '\n' - 'However, if the looked-up value is an object defining one of ' - 'the\n' - 'descriptor methods, then Python may override the default ' - 'behavior and\n' - 'invoke the descriptor method instead. Where this occurs in ' - 'the\n' - 'precedence chain depends on which descriptor methods were ' - 'defined and\n' - 'how they were called.\n' - '\n' - 'The starting point for descriptor invocation is a binding, ' - '"a.x". How\n' - 'the arguments are assembled depends on "a":\n' - '\n' - 'Direct Call\n' - ' The simplest and least common call is when user code ' - 'directly\n' - ' invokes a descriptor method: "x.__get__(a)".\n' - '\n' - 'Instance Binding\n' - ' If binding to an object instance, "a.x" is transformed ' - 'into the\n' - ' call: "type(a).__dict__[\'x\'].__get__(a, type(a))".\n' - '\n' - 'Class Binding\n' - ' If binding to a class, "A.x" is transformed into the ' - 'call:\n' - ' "A.__dict__[\'x\'].__get__(None, A)".\n' - '\n' - 'Super Binding\n' - ' A dotted lookup such as "super(A, a).x" searches\n' - ' "a.__class__.__mro__" for a base class "B" following "A" ' - 'and then\n' - ' returns "B.__dict__[\'x\'].__get__(a, A)". If not a ' - 'descriptor, "x"\n' - ' is returned unchanged.\n' - '\n' - 'For instance bindings, the precedence of descriptor ' - 'invocation depends\n' - 'on which descriptor methods are defined. A descriptor can ' - 'define any\n' - 'combination of "__get__()", "__set__()" and "__delete__()". ' - 'If it\n' - 'does not define "__get__()", then accessing the attribute ' - 'will return\n' - 'the descriptor object itself unless there is a value in the ' - 'object’s\n' - 'instance dictionary. If the descriptor defines "__set__()" ' - 'and/or\n' - '"__delete__()", it is a data descriptor; if it defines ' - 'neither, it is\n' - 'a non-data descriptor. Normally, data descriptors define ' - 'both\n' - '"__get__()" and "__set__()", while non-data descriptors have ' - 'just the\n' - '"__get__()" method. Data descriptors with "__get__()" and ' - '"__set__()"\n' - '(and/or "__delete__()") defined always override a ' - 'redefinition in an\n' - 'instance dictionary. In contrast, non-data descriptors can ' - 'be\n' - 'overridden by instances.\n' - '\n' - 'Python methods (including those decorated with ' - '"@staticmethod" and\n' - '"@classmethod") are implemented as non-data descriptors. ' - 'Accordingly,\n' - 'instances can redefine and override methods. This allows ' - 'individual\n' - 'instances to acquire behaviors that differ from other ' - 'instances of the\n' - 'same class.\n' - '\n' - 'The "property()" function is implemented as a data ' - 'descriptor.\n' - 'Accordingly, instances cannot override the behavior of a ' - 'property.\n' - '\n' - '\n' - '__slots__\n' - '---------\n' - '\n' - '*__slots__* allow us to explicitly declare data members ' - '(like\n' - 'properties) and deny the creation of "__dict__" and ' - '*__weakref__*\n' - '(unless explicitly declared in *__slots__* or available in a ' - 'parent.)\n' - '\n' - 'The space saved over using "__dict__" can be significant. ' - 'Attribute\n' - 'lookup speed can be significantly improved as well.\n' - '\n' - 'object.__slots__\n' - '\n' - ' This class variable can be assigned a string, iterable, ' - 'or sequence\n' - ' of strings with variable names used by instances. ' - '*__slots__*\n' - ' reserves space for the declared variables and prevents ' - 'the\n' - ' automatic creation of "__dict__" and *__weakref__* for ' - 'each\n' - ' instance.\n' - '\n' - 'Notes on using *__slots__*:\n' - '\n' - '* When inheriting from a class without *__slots__*, the ' - '"__dict__" and\n' - ' *__weakref__* attribute of the instances will always be ' - 'accessible.\n' - '\n' - '* Without a "__dict__" variable, instances cannot be ' - 'assigned new\n' - ' variables not listed in the *__slots__* definition. ' - 'Attempts to\n' - ' assign to an unlisted variable name raises ' - '"AttributeError". If\n' - ' dynamic assignment of new variables is desired, then add\n' - ' "\'__dict__\'" to the sequence of strings in the ' - '*__slots__*\n' - ' declaration.\n' - '\n' - '* Without a *__weakref__* variable for each instance, ' - 'classes defining\n' - ' *__slots__* do not support "weak references" to its ' - 'instances. If\n' - ' weak reference support is needed, then add ' - '"\'__weakref__\'" to the\n' - ' sequence of strings in the *__slots__* declaration.\n' - '\n' - '* *__slots__* are implemented at the class level by ' - 'creating\n' - ' descriptors for each variable name. As a result, class ' - 'attributes\n' - ' cannot be used to set default values for instance ' - 'variables defined\n' - ' by *__slots__*; otherwise, the class attribute would ' - 'overwrite the\n' - ' descriptor assignment.\n' - '\n' - '* The action of a *__slots__* declaration is not limited to ' - 'the class\n' - ' where it is defined. *__slots__* declared in parents are ' - 'available\n' - ' in child classes. However, instances of a child subclass ' - 'will get a\n' - ' "__dict__" and *__weakref__* unless the subclass also ' - 'defines\n' - ' *__slots__* (which should only contain names of any ' - '*additional*\n' - ' slots).\n' - '\n' - '* If a class defines a slot also defined in a base class, ' - 'the instance\n' - ' variable defined by the base class slot is inaccessible ' - '(except by\n' - ' retrieving its descriptor directly from the base class). ' - 'This\n' - ' renders the meaning of the program undefined. In the ' - 'future, a\n' - ' check may be added to prevent this.\n' - '\n' - '* "TypeError" will be raised if nonempty *__slots__* are ' - 'defined for a\n' - ' class derived from a ""variable-length" built-in type" ' - 'such as\n' - ' "int", "bytes", and "tuple".\n' - '\n' - '* Any non-string *iterable* may be assigned to *__slots__*.\n' - '\n' - '* If a "dictionary" is used to assign *__slots__*, the ' - 'dictionary keys\n' - ' will be used as the slot names. The values of the ' - 'dictionary can be\n' - ' used to provide per-attribute docstrings that will be ' - 'recognised by\n' - ' "inspect.getdoc()" and displayed in the output of ' - '"help()".\n' - '\n' - '* "__class__" assignment works only if both classes have the ' - 'same\n' - ' *__slots__*.\n' - '\n' - '* Multiple inheritance with multiple slotted parent classes ' - 'can be\n' - ' used, but only one parent is allowed to have attributes ' - 'created by\n' - ' slots (the other bases must have empty slot layouts) - ' - 'violations\n' - ' raise "TypeError".\n' - '\n' - '* If an *iterator* is used for *__slots__* then a ' - '*descriptor* is\n' - ' created for each of the iterator’s values. However, the ' - '*__slots__*\n' - ' attribute will be an empty iterator.\n' - '\n' - '\n' - 'Customizing class creation\n' - '==========================\n' - '\n' - 'Whenever a class inherits from another class, ' - '"__init_subclass__()" is\n' - 'called on the parent class. This way, it is possible to ' - 'write classes\n' - 'which change the behavior of subclasses. This is closely ' - 'related to\n' - 'class decorators, but where class decorators only affect the ' - 'specific\n' - 'class they’re applied to, "__init_subclass__" solely applies ' - 'to future\n' - 'subclasses of the class defining the method.\n' - '\n' - 'classmethod object.__init_subclass__(cls)\n' - '\n' - ' This method is called whenever the containing class is ' - 'subclassed.\n' - ' *cls* is then the new subclass. If defined as a normal ' - 'instance\n' - ' method, this method is implicitly converted to a class ' - 'method.\n' - '\n' - ' Keyword arguments which are given to a new class are ' - 'passed to the\n' - ' parent class’s "__init_subclass__". For compatibility ' - 'with other\n' - ' classes using "__init_subclass__", one should take out ' - 'the needed\n' - ' keyword arguments and pass the others over to the base ' - 'class, as\n' - ' in:\n' - '\n' - ' class Philosopher:\n' - ' def __init_subclass__(cls, /, default_name, ' - '**kwargs):\n' - ' super().__init_subclass__(**kwargs)\n' - ' cls.default_name = default_name\n' - '\n' - ' class AustralianPhilosopher(Philosopher, ' - 'default_name="Bruce"):\n' - ' pass\n' - '\n' - ' The default implementation "object.__init_subclass__" ' - 'does nothing,\n' - ' but raises an error if it is called with any arguments.\n' - '\n' - ' Note:\n' - '\n' - ' The metaclass hint "metaclass" is consumed by the rest ' - 'of the\n' - ' type machinery, and is never passed to ' - '"__init_subclass__"\n' - ' implementations. The actual metaclass (rather than the ' - 'explicit\n' - ' hint) can be accessed as "type(cls)".\n' - '\n' - ' Added in version 3.6.\n' - '\n' - 'When a class is created, "type.__new__()" scans the class ' - 'variables\n' - 'and makes callbacks to those with a "__set_name__()" hook.\n' - '\n' - 'object.__set_name__(self, owner, name)\n' - '\n' - ' Automatically called at the time the owning class *owner* ' - 'is\n' - ' created. The object has been assigned to *name* in that ' - 'class:\n' - '\n' - ' class A:\n' - ' x = C() # Automatically calls: x.__set_name__(A, ' - "'x')\n" - '\n' - ' If the class variable is assigned after the class is ' - 'created,\n' - ' "__set_name__()" will not be called automatically. If ' - 'needed,\n' - ' "__set_name__()" can be called directly:\n' - '\n' - ' class A:\n' - ' pass\n' - '\n' - ' c = C()\n' - ' A.x = c # The hook is not called\n' - " c.__set_name__(A, 'x') # Manually invoke the hook\n" - '\n' - ' See Creating the class object for more details.\n' - '\n' - ' Added in version 3.6.\n' - '\n' - '\n' - 'Metaclasses\n' - '-----------\n' - '\n' - 'By default, classes are constructed using "type()". The ' - 'class body is\n' - 'executed in a new namespace and the class name is bound ' - 'locally to the\n' - 'result of "type(name, bases, namespace)".\n' - '\n' - 'The class creation process can be customized by passing the\n' - '"metaclass" keyword argument in the class definition line, ' - 'or by\n' - 'inheriting from an existing class that included such an ' - 'argument. In\n' - 'the following example, both "MyClass" and "MySubclass" are ' - 'instances\n' - 'of "Meta":\n' - '\n' - ' class Meta(type):\n' - ' pass\n' - '\n' - ' class MyClass(metaclass=Meta):\n' - ' pass\n' - '\n' - ' class MySubclass(MyClass):\n' - ' pass\n' - '\n' - 'Any other keyword arguments that are specified in the class ' - 'definition\n' - 'are passed through to all metaclass operations described ' - 'below.\n' - '\n' - 'When a class definition is executed, the following steps ' - 'occur:\n' - '\n' - '* MRO entries are resolved;\n' - '\n' - '* the appropriate metaclass is determined;\n' - '\n' - '* the class namespace is prepared;\n' - '\n' - '* the class body is executed;\n' - '\n' - '* the class object is created.\n' - '\n' - '\n' - 'Resolving MRO entries\n' - '---------------------\n' - '\n' - 'object.__mro_entries__(self, bases)\n' - '\n' - ' If a base that appears in a class definition is not an ' - 'instance of\n' - ' "type", then an "__mro_entries__()" method is searched on ' - 'the base.\n' - ' If an "__mro_entries__()" method is found, the base is ' - 'substituted\n' - ' with the result of a call to "__mro_entries__()" when ' - 'creating the\n' - ' class. The method is called with the original bases tuple ' - 'passed to\n' - ' the *bases* parameter, and must return a tuple of classes ' - 'that will\n' - ' be used instead of the base. The returned tuple may be ' - 'empty: in\n' - ' these cases, the original base is ignored.\n' - '\n' - 'See also:\n' - '\n' - ' "types.resolve_bases()"\n' - ' Dynamically resolve bases that are not instances of ' - '"type".\n' - '\n' - ' "types.get_original_bases()"\n' - ' Retrieve a class’s “original bases” prior to ' - 'modifications by\n' - ' "__mro_entries__()".\n' - '\n' - ' **PEP 560**\n' - ' Core support for typing module and generic types.\n' - '\n' - '\n' - 'Determining the appropriate metaclass\n' - '-------------------------------------\n' - '\n' - 'The appropriate metaclass for a class definition is ' - 'determined as\n' - 'follows:\n' - '\n' - '* if no bases and no explicit metaclass are given, then ' - '"type()" is\n' - ' used;\n' - '\n' - '* if an explicit metaclass is given and it is *not* an ' - 'instance of\n' - ' "type()", then it is used directly as the metaclass;\n' - '\n' - '* if an instance of "type()" is given as the explicit ' - 'metaclass, or\n' - ' bases are defined, then the most derived metaclass is ' - 'used.\n' - '\n' - 'The most derived metaclass is selected from the explicitly ' - 'specified\n' - 'metaclass (if any) and the metaclasses (i.e. "type(cls)") of ' - 'all\n' - 'specified base classes. The most derived metaclass is one ' - 'which is a\n' - 'subtype of *all* of these candidate metaclasses. If none of ' - 'the\n' - 'candidate metaclasses meets that criterion, then the class ' - 'definition\n' - 'will fail with "TypeError".\n' - '\n' - '\n' - 'Preparing the class namespace\n' - '-----------------------------\n' - '\n' - 'Once the appropriate metaclass has been identified, then the ' - 'class\n' - 'namespace is prepared. If the metaclass has a "__prepare__" ' - 'attribute,\n' - 'it is called as "namespace = metaclass.__prepare__(name, ' - 'bases,\n' - '**kwds)" (where the additional keyword arguments, if any, ' - 'come from\n' - 'the class definition). The "__prepare__" method should be ' - 'implemented\n' - 'as a "classmethod". The namespace returned by "__prepare__" ' - 'is passed\n' - 'in to "__new__", but when the final class object is created ' - 'the\n' - 'namespace is copied into a new "dict".\n' - '\n' - 'If the metaclass has no "__prepare__" attribute, then the ' - 'class\n' - 'namespace is initialised as an empty ordered mapping.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3115** - Metaclasses in Python 3000\n' - ' Introduced the "__prepare__" namespace hook\n' - '\n' - '\n' - 'Executing the class body\n' - '------------------------\n' - '\n' - 'The class body is executed (approximately) as "exec(body, ' - 'globals(),\n' - 'namespace)". The key difference from a normal call to ' - '"exec()" is that\n' - 'lexical scoping allows the class body (including any ' - 'methods) to\n' - 'reference names from the current and outer scopes when the ' - 'class\n' - 'definition occurs inside a function.\n' - '\n' - 'However, even when the class definition occurs inside the ' - 'function,\n' - 'methods defined inside the class still cannot see names ' - 'defined at the\n' - 'class scope. Class variables must be accessed through the ' - 'first\n' - 'parameter of instance or class methods, or through the ' - 'implicit\n' - 'lexically scoped "__class__" reference described in the next ' - 'section.\n' - '\n' - '\n' - 'Creating the class object\n' - '-------------------------\n' - '\n' - 'Once the class namespace has been populated by executing the ' - 'class\n' - 'body, the class object is created by calling ' - '"metaclass(name, bases,\n' - 'namespace, **kwds)" (the additional keywords passed here are ' - 'the same\n' - 'as those passed to "__prepare__").\n' - '\n' - 'This class object is the one that will be referenced by the ' - 'zero-\n' - 'argument form of "super()". "__class__" is an implicit ' - 'closure\n' - 'reference created by the compiler if any methods in a class ' - 'body refer\n' - 'to either "__class__" or "super". This allows the zero ' - 'argument form\n' - 'of "super()" to correctly identify the class being defined ' - 'based on\n' - 'lexical scoping, while the class or instance that was used ' - 'to make the\n' - 'current call is identified based on the first argument ' - 'passed to the\n' - 'method.\n' - '\n' - '**CPython implementation detail:** In CPython 3.6 and later, ' - 'the\n' - '"__class__" cell is passed to the metaclass as a ' - '"__classcell__" entry\n' - 'in the class namespace. If present, this must be propagated ' - 'up to the\n' - '"type.__new__" call in order for the class to be ' - 'initialised\n' - 'correctly. Failing to do so will result in a "RuntimeError" ' - 'in Python\n' - '3.8.\n' - '\n' - 'When using the default metaclass "type", or any metaclass ' - 'that\n' - 'ultimately calls "type.__new__", the following additional\n' - 'customization steps are invoked after creating the class ' - 'object:\n' - '\n' - '1. The "type.__new__" method collects all of the attributes ' - 'in the\n' - ' class namespace that define a "__set_name__()" method;\n' - '\n' - '2. Those "__set_name__" methods are called with the class ' - 'being\n' - ' defined and the assigned name of that particular ' - 'attribute;\n' - '\n' - '3. The "__init_subclass__()" hook is called on the immediate ' - 'parent of\n' - ' the new class in its method resolution order.\n' - '\n' - 'After the class object is created, it is passed to the ' - 'class\n' - 'decorators included in the class definition (if any) and the ' - 'resulting\n' - 'object is bound in the local namespace as the defined ' - 'class.\n' - '\n' - 'When a new class is created by "type.__new__", the object ' - 'provided as\n' - 'the namespace parameter is copied to a new ordered mapping ' - 'and the\n' - 'original object is discarded. The new copy is wrapped in a ' - 'read-only\n' - 'proxy, which becomes the "__dict__" attribute of the class ' - 'object.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3135** - New super\n' - ' Describes the implicit "__class__" closure reference\n' - '\n' - '\n' - 'Uses for metaclasses\n' - '--------------------\n' - '\n' - 'The potential uses for metaclasses are boundless. Some ideas ' - 'that have\n' - 'been explored include enum, logging, interface checking, ' - 'automatic\n' - 'delegation, automatic property creation, proxies, ' - 'frameworks, and\n' - 'automatic resource locking/synchronization.\n' - '\n' - '\n' - 'Customizing instance and subclass checks\n' - '========================================\n' - '\n' - 'The following methods are used to override the default ' - 'behavior of the\n' - '"isinstance()" and "issubclass()" built-in functions.\n' - '\n' - 'In particular, the metaclass "abc.ABCMeta" implements these ' - 'methods in\n' - 'order to allow the addition of Abstract Base Classes (ABCs) ' - 'as\n' - '“virtual base classes” to any class or type (including ' - 'built-in\n' - 'types), including other ABCs.\n' - '\n' - 'type.__instancecheck__(self, instance)\n' - '\n' - ' Return true if *instance* should be considered a (direct ' - 'or\n' - ' indirect) instance of *class*. If defined, called to ' - 'implement\n' - ' "isinstance(instance, class)".\n' - '\n' - 'type.__subclasscheck__(self, subclass)\n' - '\n' - ' Return true if *subclass* should be considered a (direct ' - 'or\n' - ' indirect) subclass of *class*. If defined, called to ' - 'implement\n' - ' "issubclass(subclass, class)".\n' - '\n' - 'Note that these methods are looked up on the type ' - '(metaclass) of a\n' - 'class. They cannot be defined as class methods in the ' - 'actual class.\n' - 'This is consistent with the lookup of special methods that ' - 'are called\n' - 'on instances, only in this case the instance is itself a ' - 'class.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 3119** - Introducing Abstract Base Classes\n' - ' Includes the specification for customizing ' - '"isinstance()" and\n' - ' "issubclass()" behavior through "__instancecheck__()" ' - 'and\n' - ' "__subclasscheck__()", with motivation for this ' - 'functionality in\n' - ' the context of adding Abstract Base Classes (see the ' - '"abc"\n' - ' module) to the language.\n' - '\n' - '\n' - 'Emulating generic types\n' - '=======================\n' - '\n' - 'When using *type annotations*, it is often useful to ' - '*parameterize* a\n' - '*generic type* using Python’s square-brackets notation. For ' - 'example,\n' - 'the annotation "list[int]" might be used to signify a "list" ' - 'in which\n' - 'all the elements are of type "int".\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 484** - Type Hints\n' - ' Introducing Python’s framework for type annotations\n' - '\n' - ' Generic Alias Types\n' - ' Documentation for objects representing parameterized ' - 'generic\n' - ' classes\n' - '\n' - ' Generics, user-defined generics and "typing.Generic"\n' - ' Documentation on how to implement generic classes that ' - 'can be\n' - ' parameterized at runtime and understood by static ' - 'type-checkers.\n' - '\n' - 'A class can *generally* only be parameterized if it defines ' - 'the\n' - 'special class method "__class_getitem__()".\n' - '\n' - 'classmethod object.__class_getitem__(cls, key)\n' - '\n' - ' Return an object representing the specialization of a ' - 'generic class\n' - ' by type arguments found in *key*.\n' - '\n' - ' When defined on a class, "__class_getitem__()" is ' - 'automatically a\n' - ' class method. As such, there is no need for it to be ' - 'decorated with\n' - ' "@classmethod" when it is defined.\n' - '\n' - '\n' - 'The purpose of *__class_getitem__*\n' - '----------------------------------\n' - '\n' - 'The purpose of "__class_getitem__()" is to allow runtime\n' - 'parameterization of standard-library generic classes in ' - 'order to more\n' - 'easily apply *type hints* to these classes.\n' - '\n' - 'To implement custom generic classes that can be ' - 'parameterized at\n' - 'runtime and understood by static type-checkers, users should ' - 'either\n' - 'inherit from a standard library class that already ' - 'implements\n' - '"__class_getitem__()", or inherit from "typing.Generic", ' - 'which has its\n' - 'own implementation of "__class_getitem__()".\n' - '\n' - 'Custom implementations of "__class_getitem__()" on classes ' - 'defined\n' - 'outside of the standard library may not be understood by ' - 'third-party\n' - 'type-checkers such as mypy. Using "__class_getitem__()" on ' - 'any class\n' - 'for purposes other than type hinting is discouraged.\n' - '\n' - '\n' - '*__class_getitem__* versus *__getitem__*\n' - '----------------------------------------\n' - '\n' - 'Usually, the subscription of an object using square brackets ' - 'will call\n' - 'the "__getitem__()" instance method defined on the object’s ' - 'class.\n' - 'However, if the object being subscribed is itself a class, ' - 'the class\n' - 'method "__class_getitem__()" may be called instead.\n' - '"__class_getitem__()" should return a GenericAlias object if ' - 'it is\n' - 'properly defined.\n' - '\n' - 'Presented with the *expression* "obj[x]", the Python ' - 'interpreter\n' - 'follows something like the following process to decide ' - 'whether\n' - '"__getitem__()" or "__class_getitem__()" should be called:\n' - '\n' - ' from inspect import isclass\n' - '\n' - ' def subscribe(obj, x):\n' - ' """Return the result of the expression \'obj[x]\'"""\n' - '\n' - ' class_of_obj = type(obj)\n' - '\n' - ' # If the class of obj defines __getitem__,\n' - ' # call class_of_obj.__getitem__(obj, x)\n' - " if hasattr(class_of_obj, '__getitem__'):\n" - ' return class_of_obj.__getitem__(obj, x)\n' - '\n' - ' # Else, if obj is a class and defines ' - '__class_getitem__,\n' - ' # call obj.__class_getitem__(x)\n' - ' elif isclass(obj) and hasattr(obj, ' - "'__class_getitem__'):\n" - ' return obj.__class_getitem__(x)\n' - '\n' - ' # Else, raise an exception\n' - ' else:\n' - ' raise TypeError(\n' - ' f"\'{class_of_obj.__name__}\' object is not ' - 'subscriptable"\n' - ' )\n' - '\n' - 'In Python, all classes are themselves instances of other ' - 'classes. The\n' - 'class of a class is known as that class’s *metaclass*, and ' - 'most\n' - 'classes have the "type" class as their metaclass. "type" ' - 'does not\n' - 'define "__getitem__()", meaning that expressions such as ' - '"list[int]",\n' - '"dict[str, float]" and "tuple[str, bytes]" all result in\n' - '"__class_getitem__()" being called:\n' - '\n' - ' >>> # list has class "type" as its metaclass, like most ' - 'classes:\n' - ' >>> type(list)\n' - " <class 'type'>\n" - ' >>> type(dict) == type(list) == type(tuple) == type(str) ' - '== type(bytes)\n' - ' True\n' - ' >>> # "list[int]" calls "list.__class_getitem__(int)"\n' - ' >>> list[int]\n' - ' list[int]\n' - ' >>> # list.__class_getitem__ returns a GenericAlias ' - 'object:\n' - ' >>> type(list[int])\n' - " <class 'types.GenericAlias'>\n" - '\n' - 'However, if a class has a custom metaclass that defines\n' - '"__getitem__()", subscribing the class may result in ' - 'different\n' - 'behaviour. An example of this can be found in the "enum" ' - 'module:\n' - '\n' - ' >>> from enum import Enum\n' - ' >>> class Menu(Enum):\n' - ' ... """A breakfast menu"""\n' - " ... SPAM = 'spam'\n" - " ... BACON = 'bacon'\n" - ' ...\n' - ' >>> # Enum classes have a custom metaclass:\n' - ' >>> type(Menu)\n' - " <class 'enum.EnumMeta'>\n" - ' >>> # EnumMeta defines __getitem__,\n' - ' >>> # so __class_getitem__ is not called,\n' - ' >>> # and the result is not a GenericAlias object:\n' - " >>> Menu['SPAM']\n" - " <Menu.SPAM: 'spam'>\n" - " >>> type(Menu['SPAM'])\n" - " <enum 'Menu'>\n" - '\n' - 'See also:\n' - '\n' - ' **PEP 560** - Core Support for typing module and generic ' - 'types\n' - ' Introducing "__class_getitem__()", and outlining when ' - 'a\n' - ' subscription results in "__class_getitem__()" being ' - 'called\n' - ' instead of "__getitem__()"\n' - '\n' - '\n' - 'Emulating callable objects\n' - '==========================\n' - '\n' - 'object.__call__(self[, args...])\n' - '\n' - ' Called when the instance is “called” as a function; if ' - 'this method\n' - ' is defined, "x(arg1, arg2, ...)" roughly translates to\n' - ' "type(x).__call__(x, arg1, ...)". The "object" class ' - 'itself does\n' - ' not provide this method.\n' - '\n' - '\n' - 'Emulating container types\n' - '=========================\n' - '\n' - 'The following methods can be defined to implement container ' - 'objects.\n' - 'None of them are provided by the "object" class itself. ' - 'Containers\n' - 'usually are *sequences* (such as "lists" or "tuples") or ' - '*mappings*\n' - '(like *dictionaries*), but can represent other containers as ' - 'well.\n' - 'The first set of methods is used either to emulate a ' - 'sequence or to\n' - 'emulate a mapping; the difference is that for a sequence, ' - 'the\n' - 'allowable keys should be the integers *k* for which "0 <= k ' - '< N" where\n' - '*N* is the length of the sequence, or "slice" objects, which ' - 'define a\n' - 'range of items. It is also recommended that mappings ' - 'provide the\n' - 'methods "keys()", "values()", "items()", "get()", ' - '"clear()",\n' - '"setdefault()", "pop()", "popitem()", "copy()", and ' - '"update()"\n' - 'behaving similar to those for Python’s standard "dictionary" ' - 'objects.\n' - 'The "collections.abc" module provides a "MutableMapping" ' - '*abstract\n' - 'base class* to help create those methods from a base set of\n' - '"__getitem__()", "__setitem__()", "__delitem__()", and ' - '"keys()".\n' - 'Mutable sequences should provide methods "append()", ' - '"count()",\n' - '"index()", "extend()", "insert()", "pop()", "remove()", ' - '"reverse()"\n' - 'and "sort()", like Python standard "list" objects. Finally, ' - 'sequence\n' - 'types should implement addition (meaning concatenation) and\n' - 'multiplication (meaning repetition) by defining the methods\n' - '"__add__()", "__radd__()", "__iadd__()", "__mul__()", ' - '"__rmul__()" and\n' - '"__imul__()" described below; they should not define other ' - 'numerical\n' - 'operators. It is recommended that both mappings and ' - 'sequences\n' - 'implement the "__contains__()" method to allow efficient use ' - 'of the\n' - '"in" operator; for mappings, "in" should search the ' - 'mapping’s keys;\n' - 'for sequences, it should search through the values. It is ' - 'further\n' - 'recommended that both mappings and sequences implement the\n' - '"__iter__()" method to allow efficient iteration through ' - 'the\n' - 'container; for mappings, "__iter__()" should iterate through ' - 'the\n' - 'object’s keys; for sequences, it should iterate through the ' - 'values.\n' - '\n' - 'object.__len__(self)\n' - '\n' - ' Called to implement the built-in function "len()". ' - 'Should return\n' - ' the length of the object, an integer ">=" 0. Also, an ' - 'object that\n' - ' doesn’t define a "__bool__()" method and whose ' - '"__len__()" method\n' - ' returns zero is considered to be false in a Boolean ' - 'context.\n' - '\n' - ' **CPython implementation detail:** In CPython, the length ' - 'is\n' - ' required to be at most "sys.maxsize". If the length is ' - 'larger than\n' - ' "sys.maxsize" some features (such as "len()") may raise\n' - ' "OverflowError". To prevent raising "OverflowError" by ' - 'truth value\n' - ' testing, an object must define a "__bool__()" method.\n' - '\n' - 'object.__length_hint__(self)\n' - '\n' - ' Called to implement "operator.length_hint()". Should ' - 'return an\n' - ' estimated length for the object (which may be greater or ' - 'less than\n' - ' the actual length). The length must be an integer ">=" 0. ' - 'The\n' - ' return value may also be "NotImplemented", which is ' - 'treated the\n' - ' same as if the "__length_hint__" method didn’t exist at ' - 'all. This\n' - ' method is purely an optimization and is never required ' - 'for\n' - ' correctness.\n' - '\n' - ' Added in version 3.4.\n' - '\n' - 'Note:\n' - '\n' - ' Slicing is done exclusively with the following three ' - 'methods. A\n' - ' call like\n' - '\n' - ' a[1:2] = b\n' - '\n' - ' is translated to\n' - '\n' - ' a[slice(1, 2, None)] = b\n' - '\n' - ' and so forth. Missing slice items are always filled in ' - 'with "None".\n' - '\n' - 'object.__getitem__(self, key)\n' - '\n' - ' Called to implement evaluation of "self[key]". For ' - '*sequence*\n' - ' types, the accepted keys should be integers. Optionally, ' - 'they may\n' - ' support "slice" objects as well. Negative index support ' - 'is also\n' - ' optional. If *key* is of an inappropriate type, ' - '"TypeError" may be\n' - ' raised; if *key* is a value outside the set of indexes ' - 'for the\n' - ' sequence (after any special interpretation of negative ' - 'values),\n' - ' "IndexError" should be raised. For *mapping* types, if ' - '*key* is\n' - ' missing (not in the container), "KeyError" should be ' - 'raised.\n' - '\n' - ' Note:\n' - '\n' - ' "for" loops expect that an "IndexError" will be raised ' - 'for\n' - ' illegal indexes to allow proper detection of the end of ' - 'the\n' - ' sequence.\n' - '\n' - ' Note:\n' - '\n' - ' When subscripting a *class*, the special class method\n' - ' "__class_getitem__()" may be called instead of ' - '"__getitem__()".\n' - ' See __class_getitem__ versus __getitem__ for more ' - 'details.\n' - '\n' - 'object.__setitem__(self, key, value)\n' - '\n' - ' Called to implement assignment to "self[key]". Same note ' - 'as for\n' - ' "__getitem__()". This should only be implemented for ' - 'mappings if\n' - ' the objects support changes to the values for keys, or if ' - 'new keys\n' - ' can be added, or for sequences if elements can be ' - 'replaced. The\n' - ' same exceptions should be raised for improper *key* ' - 'values as for\n' - ' the "__getitem__()" method.\n' - '\n' - 'object.__delitem__(self, key)\n' - '\n' - ' Called to implement deletion of "self[key]". Same note ' - 'as for\n' - ' "__getitem__()". This should only be implemented for ' - 'mappings if\n' - ' the objects support removal of keys, or for sequences if ' - 'elements\n' - ' can be removed from the sequence. The same exceptions ' - 'should be\n' - ' raised for improper *key* values as for the ' - '"__getitem__()" method.\n' - '\n' - 'object.__missing__(self, key)\n' - '\n' - ' Called by "dict"."__getitem__()" to implement "self[key]" ' - 'for dict\n' - ' subclasses when key is not in the dictionary.\n' - '\n' - 'object.__iter__(self)\n' - '\n' - ' This method is called when an *iterator* is required for ' - 'a\n' - ' container. This method should return a new iterator ' - 'object that can\n' - ' iterate over all the objects in the container. For ' - 'mappings, it\n' - ' should iterate over the keys of the container.\n' - '\n' - 'object.__reversed__(self)\n' - '\n' - ' Called (if present) by the "reversed()" built-in to ' - 'implement\n' - ' reverse iteration. It should return a new iterator ' - 'object that\n' - ' iterates over all the objects in the container in reverse ' - 'order.\n' - '\n' - ' If the "__reversed__()" method is not provided, the ' - '"reversed()"\n' - ' built-in will fall back to using the sequence protocol ' - '("__len__()"\n' - ' and "__getitem__()"). Objects that support the sequence ' - 'protocol\n' - ' should only provide "__reversed__()" if they can provide ' - 'an\n' - ' implementation that is more efficient than the one ' - 'provided by\n' - ' "reversed()".\n' - '\n' - 'The membership test operators ("in" and "not in") are ' - 'normally\n' - 'implemented as an iteration through a container. However, ' - 'container\n' - 'objects can supply the following special method with a more ' - 'efficient\n' - 'implementation, which also does not require the object be ' - 'iterable.\n' - '\n' - 'object.__contains__(self, item)\n' - '\n' - ' Called to implement membership test operators. Should ' - 'return true\n' - ' if *item* is in *self*, false otherwise. For mapping ' - 'objects, this\n' - ' should consider the keys of the mapping rather than the ' - 'values or\n' - ' the key-item pairs.\n' - '\n' - ' For objects that don’t define "__contains__()", the ' - 'membership test\n' - ' first tries iteration via "__iter__()", then the old ' - 'sequence\n' - ' iteration protocol via "__getitem__()", see this section ' - 'in the\n' - ' language reference.\n' - '\n' - '\n' - 'Emulating numeric types\n' - '=======================\n' - '\n' - 'The following methods can be defined to emulate numeric ' - 'objects.\n' - 'Methods corresponding to operations that are not supported ' - 'by the\n' - 'particular kind of number implemented (e.g., bitwise ' - 'operations for\n' - 'non-integral numbers) should be left undefined.\n' - '\n' - 'object.__add__(self, other)\n' - 'object.__sub__(self, other)\n' - 'object.__mul__(self, other)\n' - 'object.__matmul__(self, other)\n' - 'object.__truediv__(self, other)\n' - 'object.__floordiv__(self, other)\n' - 'object.__mod__(self, other)\n' - 'object.__divmod__(self, other)\n' - 'object.__pow__(self, other[, modulo])\n' - 'object.__lshift__(self, other)\n' - 'object.__rshift__(self, other)\n' - 'object.__and__(self, other)\n' - 'object.__xor__(self, other)\n' - 'object.__or__(self, other)\n' - '\n' - ' These methods are called to implement the binary ' - 'arithmetic\n' - ' operations ("+", "-", "*", "@", "/", "//", "%", ' - '"divmod()",\n' - ' "pow()", "**", "<<", ">>", "&", "^", "|"). For instance, ' - 'to\n' - ' evaluate the expression "x + y", where *x* is an instance ' - 'of a\n' - ' class that has an "__add__()" method, "type(x).__add__(x, ' - 'y)" is\n' - ' called. The "__divmod__()" method should be the ' - 'equivalent to\n' - ' using "__floordiv__()" and "__mod__()"; it should not be ' - 'related to\n' - ' "__truediv__()". Note that "__pow__()" should be defined ' - 'to accept\n' - ' an optional third argument if the ternary version of the ' - 'built-in\n' - ' "pow()" function is to be supported.\n' - '\n' - ' If one of those methods does not support the operation ' - 'with the\n' - ' supplied arguments, it should return "NotImplemented".\n' - '\n' - 'object.__radd__(self, other)\n' - 'object.__rsub__(self, other)\n' - 'object.__rmul__(self, other)\n' - 'object.__rmatmul__(self, other)\n' - 'object.__rtruediv__(self, other)\n' - 'object.__rfloordiv__(self, other)\n' - 'object.__rmod__(self, other)\n' - 'object.__rdivmod__(self, other)\n' - 'object.__rpow__(self, other[, modulo])\n' - 'object.__rlshift__(self, other)\n' - 'object.__rrshift__(self, other)\n' - 'object.__rand__(self, other)\n' - 'object.__rxor__(self, other)\n' - 'object.__ror__(self, other)\n' - '\n' - ' These methods are called to implement the binary ' - 'arithmetic\n' - ' operations ("+", "-", "*", "@", "/", "//", "%", ' - '"divmod()",\n' - ' "pow()", "**", "<<", ">>", "&", "^", "|") with reflected ' - '(swapped)\n' - ' operands. These functions are only called if the ' - 'operands are of\n' - ' different types, when the left operand does not support ' - 'the\n' - ' corresponding operation [3], or the right operand’s class ' - 'is\n' - ' derived from the left operand’s class. [4] For instance, ' - 'to\n' - ' evaluate the expression "x - y", where *y* is an instance ' - 'of a\n' - ' class that has an "__rsub__()" method, ' - '"type(y).__rsub__(y, x)" is\n' - ' called if "type(x).__sub__(x, y)" returns ' - '"NotImplemented" or\n' - ' "type(y)" is a subclass of "type(x)". [5]\n' - '\n' - ' Note that ternary "pow()" will not try calling ' - '"__rpow__()" (the\n' - ' coercion rules would become too complicated).\n' - '\n' - ' Note:\n' - '\n' - ' If the right operand’s type is a subclass of the left ' - 'operand’s\n' - ' type and that subclass provides a different ' - 'implementation of the\n' - ' reflected method for the operation, this method will be ' - 'called\n' - ' before the left operand’s non-reflected method. This ' - 'behavior\n' - ' allows subclasses to override their ancestors’ ' - 'operations.\n' - '\n' - 'object.__iadd__(self, other)\n' - 'object.__isub__(self, other)\n' - 'object.__imul__(self, other)\n' - 'object.__imatmul__(self, other)\n' - 'object.__itruediv__(self, other)\n' - 'object.__ifloordiv__(self, other)\n' - 'object.__imod__(self, other)\n' - 'object.__ipow__(self, other[, modulo])\n' - 'object.__ilshift__(self, other)\n' - 'object.__irshift__(self, other)\n' - 'object.__iand__(self, other)\n' - 'object.__ixor__(self, other)\n' - 'object.__ior__(self, other)\n' - '\n' - ' These methods are called to implement the augmented ' - 'arithmetic\n' - ' assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", ' - '"**=",\n' - ' "<<=", ">>=", "&=", "^=", "|="). These methods should ' - 'attempt to\n' - ' do the operation in-place (modifying *self*) and return ' - 'the result\n' - ' (which could be, but does not have to be, *self*). If a ' - 'specific\n' - ' method is not defined, or if that method returns ' - '"NotImplemented",\n' - ' the augmented assignment falls back to the normal ' - 'methods. For\n' - ' instance, if *x* is an instance of a class with an ' - '"__iadd__()"\n' - ' method, "x += y" is equivalent to "x = x.__iadd__(y)" . ' - 'If\n' - ' "__iadd__()" does not exist, or if "x.__iadd__(y)" ' - 'returns\n' - ' "NotImplemented", "x.__add__(y)" and "y.__radd__(x)" are\n' - ' considered, as with the evaluation of "x + y". In ' - 'certain\n' - ' situations, augmented assignment can result in unexpected ' - 'errors\n' - ' (see Why does a_tuple[i] += [‘item’] raise an exception ' - 'when the\n' - ' addition works?), but this behavior is in fact part of ' - 'the data\n' - ' model.\n' - '\n' - 'object.__neg__(self)\n' - 'object.__pos__(self)\n' - 'object.__abs__(self)\n' - 'object.__invert__(self)\n' - '\n' - ' Called to implement the unary arithmetic operations ("-", ' - '"+",\n' - ' "abs()" and "~").\n' - '\n' - 'object.__complex__(self)\n' - 'object.__int__(self)\n' - 'object.__float__(self)\n' - '\n' - ' Called to implement the built-in functions "complex()", ' - '"int()" and\n' - ' "float()". Should return a value of the appropriate ' - 'type.\n' - '\n' - 'object.__index__(self)\n' - '\n' - ' Called to implement "operator.index()", and whenever ' - 'Python needs\n' - ' to losslessly convert the numeric object to an integer ' - 'object (such\n' - ' as in slicing, or in the built-in "bin()", "hex()" and ' - '"oct()"\n' - ' functions). Presence of this method indicates that the ' - 'numeric\n' - ' object is an integer type. Must return an integer.\n' - '\n' - ' If "__int__()", "__float__()" and "__complex__()" are not ' - 'defined\n' - ' then corresponding built-in functions "int()", "float()" ' - 'and\n' - ' "complex()" fall back to "__index__()".\n' - '\n' - 'object.__round__(self[, ndigits])\n' - 'object.__trunc__(self)\n' - 'object.__floor__(self)\n' - 'object.__ceil__(self)\n' - '\n' - ' Called to implement the built-in function "round()" and ' - '"math"\n' - ' functions "trunc()", "floor()" and "ceil()". Unless ' - '*ndigits* is\n' - ' passed to "__round__()" all these methods should return ' - 'the value\n' - ' of the object truncated to an "Integral" (typically an ' - '"int").\n' - '\n' - ' Changed in version 3.14: "int()" no longer delegates to ' - 'the\n' - ' "__trunc__()" method.\n' - '\n' - '\n' - 'With Statement Context Managers\n' - '===============================\n' - '\n' - 'A *context manager* is an object that defines the runtime ' - 'context to\n' - 'be established when executing a "with" statement. The ' - 'context manager\n' - 'handles the entry into, and the exit from, the desired ' - 'runtime context\n' - 'for the execution of the block of code. Context managers ' - 'are normally\n' - 'invoked using the "with" statement (described in section The ' - 'with\n' - 'statement), but can also be used by directly invoking their ' - 'methods.\n' - '\n' - 'Typical uses of context managers include saving and ' - 'restoring various\n' - 'kinds of global state, locking and unlocking resources, ' - 'closing opened\n' - 'files, etc.\n' - '\n' - 'For more information on context managers, see Context ' - 'Manager Types.\n' - 'The "object" class itself does not provide the context ' - 'manager\n' - 'methods.\n' - '\n' - 'object.__enter__(self)\n' - '\n' - ' Enter the runtime context related to this object. The ' - '"with"\n' - ' statement will bind this method’s return value to the ' - 'target(s)\n' - ' specified in the "as" clause of the statement, if any.\n' - '\n' - 'object.__exit__(self, exc_type, exc_value, traceback)\n' - '\n' - ' Exit the runtime context related to this object. The ' - 'parameters\n' - ' describe the exception that caused the context to be ' - 'exited. If the\n' - ' context was exited without an exception, all three ' - 'arguments will\n' - ' be "None".\n' - '\n' - ' If an exception is supplied, and the method wishes to ' - 'suppress the\n' - ' exception (i.e., prevent it from being propagated), it ' - 'should\n' - ' return a true value. Otherwise, the exception will be ' - 'processed\n' - ' normally upon exit from this method.\n' - '\n' - ' Note that "__exit__()" methods should not reraise the ' - 'passed-in\n' - ' exception; this is the caller’s responsibility.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 343** - The “with” statement\n' - ' The specification, background, and examples for the ' - 'Python "with"\n' - ' statement.\n' - '\n' - '\n' - 'Customizing positional arguments in class pattern matching\n' - '==========================================================\n' - '\n' - 'When using a class name in a pattern, positional arguments ' - 'in the\n' - 'pattern are not allowed by default, i.e. "case MyClass(x, ' - 'y)" is\n' - 'typically invalid without special support in "MyClass". To ' - 'be able to\n' - 'use that kind of pattern, the class needs to define a ' - '*__match_args__*\n' - 'attribute.\n' - '\n' - 'object.__match_args__\n' - '\n' - ' This class variable can be assigned a tuple of strings. ' - 'When this\n' - ' class is used in a class pattern with positional ' - 'arguments, each\n' - ' positional argument will be converted into a keyword ' - 'argument,\n' - ' using the corresponding value in *__match_args__* as the ' - 'keyword.\n' - ' The absence of this attribute is equivalent to setting it ' - 'to "()".\n' - '\n' - 'For example, if "MyClass.__match_args__" is "("left", ' - '"center",\n' - '"right")" that means that "case MyClass(x, y)" is equivalent ' - 'to "case\n' - 'MyClass(left=x, center=y)". Note that the number of ' - 'arguments in the\n' - 'pattern must be smaller than or equal to the number of ' - 'elements in\n' - '*__match_args__*; if it is larger, the pattern match attempt ' - 'will\n' - 'raise a "TypeError".\n' - '\n' - 'Added in version 3.10.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 634** - Structural Pattern Matching\n' - ' The specification for the Python "match" statement.\n' - '\n' - '\n' - 'Emulating buffer types\n' - '======================\n' - '\n' - 'The buffer protocol provides a way for Python objects to ' - 'expose\n' - 'efficient access to a low-level memory array. This protocol ' - 'is\n' - 'implemented by builtin types such as "bytes" and ' - '"memoryview", and\n' - 'third-party libraries may define additional buffer types.\n' - '\n' - 'While buffer types are usually implemented in C, it is also ' - 'possible\n' - 'to implement the protocol in Python.\n' - '\n' - 'object.__buffer__(self, flags)\n' - '\n' - ' Called when a buffer is requested from *self* (for ' - 'example, by the\n' - ' "memoryview" constructor). The *flags* argument is an ' - 'integer\n' - ' representing the kind of buffer requested, affecting for ' - 'example\n' - ' whether the returned buffer is read-only or writable.\n' - ' "inspect.BufferFlags" provides a convenient way to ' - 'interpret the\n' - ' flags. The method must return a "memoryview" object.\n' - '\n' - 'object.__release_buffer__(self, buffer)\n' - '\n' - ' Called when a buffer is no longer needed. The *buffer* ' - 'argument is\n' - ' a "memoryview" object that was previously returned by\n' - ' "__buffer__()". The method must release any resources ' - 'associated\n' - ' with the buffer. This method should return "None". Buffer ' - 'objects\n' - ' that do not need to perform any cleanup are not required ' - 'to\n' - ' implement this method.\n' - '\n' - 'Added in version 3.12.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 688** - Making the buffer protocol accessible in ' - 'Python\n' - ' Introduces the Python "__buffer__" and ' - '"__release_buffer__"\n' - ' methods.\n' - '\n' - ' "collections.abc.Buffer"\n' - ' ABC for buffer types.\n' - '\n' - '\n' - 'Annotations\n' - '===========\n' - '\n' - 'Functions, classes, and modules may contain *annotations*, ' - 'which are a\n' - 'way to associate information (usually *type hints*) with a ' - 'symbol.\n' - '\n' - 'object.__annotations__\n' - '\n' - ' This attribute contains the annotations for an object. It ' - 'is lazily\n' - ' evaluated, so accessing the attribute may execute ' - 'arbitrary code\n' - ' and raise exceptions. If evaluation is successful, the ' - 'attribute is\n' - ' set to a dictionary mapping from variable names to ' - 'annotations.\n' - '\n' - ' Changed in version 3.14: Annotations are now lazily ' - 'evaluated.\n' - '\n' - 'object.__annotate__(format)\n' - '\n' - ' An *annotate function*. Returns a new dictionary object ' - 'mapping\n' - ' attribute/parameter names to their annotation values.\n' - '\n' - ' Takes a format parameter specifying the format in which ' - 'annotations\n' - ' values should be provided. It must be a member of the\n' - ' "annotationlib.Format" enum, or an integer with a value\n' - ' corresponding to a member of the enum.\n' - '\n' - ' If an annotate function doesn’t support the requested ' - 'format, it\n' - ' must raise "NotImplementedError". Annotate functions must ' - 'always\n' - ' support "VALUE" format; they must not raise ' - '"NotImplementedError()"\n' - ' when called with this format.\n' - '\n' - ' When called with "VALUE" format, an annotate function ' - 'may raise\n' - ' "NameError"; it must not raise "NameError" when called ' - 'requesting\n' - ' any other format.\n' - '\n' - ' If an object does not have any annotations, ' - '"__annotate__" should\n' - ' preferably be set to "None" (it can’t be deleted), rather ' - 'than set\n' - ' to a function that returns an empty dict.\n' - '\n' - ' Added in version 3.14.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 649** — Deferred evaluation of annotation using ' - 'descriptors\n' - ' Introduces lazy evaluation of annotations and the ' - '"__annotate__"\n' - ' function.\n' - '\n' - '\n' - 'Special method lookup\n' - '=====================\n' - '\n' - 'For custom classes, implicit invocations of special methods ' - 'are only\n' - 'guaranteed to work correctly if defined on an object’s type, ' - 'not in\n' - 'the object’s instance dictionary. That behaviour is the ' - 'reason why\n' - 'the following code raises an exception:\n' - '\n' - ' >>> class C:\n' - ' ... pass\n' - ' ...\n' - ' >>> c = C()\n' - ' >>> c.__len__ = lambda: 5\n' - ' >>> len(c)\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 1, in <module>\n' - " TypeError: object of type 'C' has no len()\n" - '\n' - 'The rationale behind this behaviour lies with a number of ' - 'special\n' - 'methods such as "__hash__()" and "__repr__()" that are ' - 'implemented by\n' - 'all objects, including type objects. If the implicit lookup ' - 'of these\n' - 'methods used the conventional lookup process, they would ' - 'fail when\n' - 'invoked on the type object itself:\n' - '\n' - ' >>> 1 .__hash__() == hash(1)\n' - ' True\n' - ' >>> int.__hash__() == hash(int)\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 1, in <module>\n' - " TypeError: descriptor '__hash__' of 'int' object needs an " - 'argument\n' - '\n' - 'Incorrectly attempting to invoke an unbound method of a ' - 'class in this\n' - 'way is sometimes referred to as ‘metaclass confusion’, and ' - 'is avoided\n' - 'by bypassing the instance when looking up special methods:\n' - '\n' - ' >>> type(1).__hash__(1) == hash(1)\n' - ' True\n' - ' >>> type(int).__hash__(int) == hash(int)\n' - ' True\n' - '\n' - 'In addition to bypassing any instance attributes in the ' - 'interest of\n' - 'correctness, implicit special method lookup generally also ' - 'bypasses\n' - 'the "__getattribute__()" method even of the object’s ' - 'metaclass:\n' - '\n' - ' >>> class Meta(type):\n' - ' ... def __getattribute__(*args):\n' - ' ... print("Metaclass getattribute invoked")\n' - ' ... return type.__getattribute__(*args)\n' - ' ...\n' - ' >>> class C(object, metaclass=Meta):\n' - ' ... def __len__(self):\n' - ' ... return 10\n' - ' ... def __getattribute__(*args):\n' - ' ... print("Class getattribute invoked")\n' - ' ... return object.__getattribute__(*args)\n' - ' ...\n' - ' >>> c = C()\n' - ' >>> c.__len__() # Explicit lookup via ' - 'instance\n' - ' Class getattribute invoked\n' - ' 10\n' - ' >>> type(c).__len__(c) # Explicit lookup via ' - 'type\n' - ' Metaclass getattribute invoked\n' - ' 10\n' - ' >>> len(c) # Implicit lookup\n' - ' 10\n' - '\n' - 'Bypassing the "__getattribute__()" machinery in this fashion ' - 'provides\n' - 'significant scope for speed optimisations within the ' - 'interpreter, at\n' - 'the cost of some flexibility in the handling of special ' - 'methods (the\n' - 'special method *must* be set on the class object itself in ' - 'order to be\n' - 'consistently invoked by the interpreter).\n', - 'string-methods': 'String Methods\n' - '**************\n' - '\n' - 'Strings implement all of the common sequence operations, ' - 'along with\n' - 'the additional methods described below.\n' - '\n' - 'Strings also support two styles of string formatting, one ' - 'providing a\n' - 'large degree of flexibility and customization (see ' - '"str.format()",\n' - 'Format String Syntax and Custom String Formatting) and the ' - 'other based\n' - 'on C "printf" style formatting that handles a narrower ' - 'range of types\n' - 'and is slightly harder to use correctly, but is often ' - 'faster for the\n' - 'cases it can handle (printf-style String Formatting).\n' - '\n' - 'The Text Processing Services section of the standard ' - 'library covers a\n' - 'number of other modules that provide various text related ' - 'utilities\n' - '(including regular expression support in the "re" ' - 'module).\n' - '\n' - 'str.capitalize()\n' - '\n' - ' Return a copy of the string with its first character ' - 'capitalized\n' - ' and the rest lowercased.\n' - '\n' - ' Changed in version 3.8: The first character is now put ' - 'into\n' - ' titlecase rather than uppercase. This means that ' - 'characters like\n' - ' digraphs will only have their first letter capitalized, ' - 'instead of\n' - ' the full character.\n' - '\n' - 'str.casefold()\n' - '\n' - ' Return a casefolded copy of the string. Casefolded ' - 'strings may be\n' - ' used for caseless matching.\n' - '\n' - ' Casefolding is similar to lowercasing but more ' - 'aggressive because\n' - ' it is intended to remove all case distinctions in a ' - 'string. For\n' - ' example, the German lowercase letter "\'ß\'" is ' - 'equivalent to ""ss"".\n' - ' Since it is already lowercase, "lower()" would do ' - 'nothing to "\'ß\'";\n' - ' "casefold()" converts it to ""ss"".\n' - '\n' - ' The casefolding algorithm is described in section 3.13 ' - '‘Default\n' - ' Case Folding’ of the Unicode Standard.\n' - '\n' - ' Added in version 3.3.\n' - '\n' - 'str.center(width[, fillchar])\n' - '\n' - ' Return centered in a string of length *width*. Padding ' - 'is done\n' - ' using the specified *fillchar* (default is an ASCII ' - 'space). The\n' - ' original string is returned if *width* is less than or ' - 'equal to\n' - ' "len(s)".\n' - '\n' - 'str.count(sub[, start[, end]])\n' - '\n' - ' Return the number of non-overlapping occurrences of ' - 'substring *sub*\n' - ' in the range [*start*, *end*]. Optional arguments ' - '*start* and\n' - ' *end* are interpreted as in slice notation.\n' - '\n' - ' If *sub* is empty, returns the number of empty strings ' - 'between\n' - ' characters which is the length of the string plus one.\n' - '\n' - "str.encode(encoding='utf-8', errors='strict')\n" - '\n' - ' Return the string encoded to "bytes".\n' - '\n' - ' *encoding* defaults to "\'utf-8\'"; see Standard ' - 'Encodings for\n' - ' possible values.\n' - '\n' - ' *errors* controls how encoding errors are handled. If ' - '"\'strict\'"\n' - ' (the default), a "UnicodeError" exception is raised. ' - 'Other possible\n' - ' values are "\'ignore\'", "\'replace\'", ' - '"\'xmlcharrefreplace\'",\n' - ' "\'backslashreplace\'" and any other name registered ' - 'via\n' - ' "codecs.register_error()". See Error Handlers for ' - 'details.\n' - '\n' - ' For performance reasons, the value of *errors* is not ' - 'checked for\n' - ' validity unless an encoding error actually occurs, ' - 'Python\n' - ' Development Mode is enabled or a debug build is used.\n' - '\n' - ' Changed in version 3.1: Added support for keyword ' - 'arguments.\n' - '\n' - ' Changed in version 3.9: The value of the *errors* ' - 'argument is now\n' - ' checked in Python Development Mode and in debug mode.\n' - '\n' - 'str.endswith(suffix[, start[, end]])\n' - '\n' - ' Return "True" if the string ends with the specified ' - '*suffix*,\n' - ' otherwise return "False". *suffix* can also be a tuple ' - 'of suffixes\n' - ' to look for. With optional *start*, test beginning at ' - 'that\n' - ' position. With optional *end*, stop comparing at that ' - 'position.\n' - '\n' - 'str.expandtabs(tabsize=8)\n' - '\n' - ' Return a copy of the string where all tab characters ' - 'are replaced\n' - ' by one or more spaces, depending on the current column ' - 'and the\n' - ' given tab size. Tab positions occur every *tabsize* ' - 'characters\n' - ' (default is 8, giving tab positions at columns 0, 8, 16 ' - 'and so on).\n' - ' To expand the string, the current column is set to zero ' - 'and the\n' - ' string is examined character by character. If the ' - 'character is a\n' - ' tab ("\\t"), one or more space characters are inserted ' - 'in the result\n' - ' until the current column is equal to the next tab ' - 'position. (The\n' - ' tab character itself is not copied.) If the character ' - 'is a newline\n' - ' ("\\n") or return ("\\r"), it is copied and the current ' - 'column is\n' - ' reset to zero. Any other character is copied unchanged ' - 'and the\n' - ' current column is incremented by one regardless of how ' - 'the\n' - ' character is represented when printed.\n' - '\n' - " >>> '01\\t012\\t0123\\t01234'.expandtabs()\n" - " '01 012 0123 01234'\n" - " >>> '01\\t012\\t0123\\t01234'.expandtabs(4)\n" - " '01 012 0123 01234'\n" - '\n' - 'str.find(sub[, start[, end]])\n' - '\n' - ' Return the lowest index in the string where substring ' - '*sub* is\n' - ' found within the slice "s[start:end]". Optional ' - 'arguments *start*\n' - ' and *end* are interpreted as in slice notation. Return ' - '"-1" if\n' - ' *sub* is not found.\n' - '\n' - ' Note:\n' - '\n' - ' The "find()" method should be used only if you need ' - 'to know the\n' - ' position of *sub*. To check if *sub* is a substring ' - 'or not, use\n' - ' the "in" operator:\n' - '\n' - " >>> 'Py' in 'Python'\n" - ' True\n' - '\n' - 'str.format(*args, **kwargs)\n' - '\n' - ' Perform a string formatting operation. The string on ' - 'which this\n' - ' method is called can contain literal text or ' - 'replacement fields\n' - ' delimited by braces "{}". Each replacement field ' - 'contains either\n' - ' the numeric index of a positional argument, or the name ' - 'of a\n' - ' keyword argument. Returns a copy of the string where ' - 'each\n' - ' replacement field is replaced with the string value of ' - 'the\n' - ' corresponding argument.\n' - '\n' - ' >>> "The sum of 1 + 2 is {0}".format(1+2)\n' - " 'The sum of 1 + 2 is 3'\n" - '\n' - ' See Format String Syntax for a description of the ' - 'various\n' - ' formatting options that can be specified in format ' - 'strings.\n' - '\n' - ' Note:\n' - '\n' - ' When formatting a number ("int", "float", "complex",\n' - ' "decimal.Decimal" and subclasses) with the "n" type ' - '(ex:\n' - ' "\'{:n}\'.format(1234)"), the function temporarily ' - 'sets the\n' - ' "LC_CTYPE" locale to the "LC_NUMERIC" locale to ' - 'decode\n' - ' "decimal_point" and "thousands_sep" fields of ' - '"localeconv()" if\n' - ' they are non-ASCII or longer than 1 byte, and the ' - '"LC_NUMERIC"\n' - ' locale is different than the "LC_CTYPE" locale. This ' - 'temporary\n' - ' change affects other threads.\n' - '\n' - ' Changed in version 3.7: When formatting a number with ' - 'the "n" type,\n' - ' the function sets temporarily the "LC_CTYPE" locale to ' - 'the\n' - ' "LC_NUMERIC" locale in some cases.\n' - '\n' - 'str.format_map(mapping, /)\n' - '\n' - ' Similar to "str.format(**mapping)", except that ' - '"mapping" is used\n' - ' directly and not copied to a "dict". This is useful if ' - 'for example\n' - ' "mapping" is a dict subclass:\n' - '\n' - ' >>> class Default(dict):\n' - ' ... def __missing__(self, key):\n' - ' ... return key\n' - ' ...\n' - " >>> '{name} was born in " - "{country}'.format_map(Default(name='Guido'))\n" - " 'Guido was born in country'\n" - '\n' - ' Added in version 3.2.\n' - '\n' - 'str.index(sub[, start[, end]])\n' - '\n' - ' Like "find()", but raise "ValueError" when the ' - 'substring is not\n' - ' found.\n' - '\n' - 'str.isalnum()\n' - '\n' - ' Return "True" if all characters in the string are ' - 'alphanumeric and\n' - ' there is at least one character, "False" otherwise. A ' - 'character\n' - ' "c" is alphanumeric if one of the following returns ' - '"True":\n' - ' "c.isalpha()", "c.isdecimal()", "c.isdigit()", or ' - '"c.isnumeric()".\n' - '\n' - 'str.isalpha()\n' - '\n' - ' Return "True" if all characters in the string are ' - 'alphabetic and\n' - ' there is at least one character, "False" otherwise. ' - 'Alphabetic\n' - ' characters are those characters defined in the Unicode ' - 'character\n' - ' database as “Letter”, i.e., those with general category ' - 'property\n' - ' being one of “Lm”, “Lt”, “Lu”, “Ll”, or “Lo”. Note ' - 'that this is\n' - ' different from the Alphabetic property defined in the ' - 'section 4.10\n' - ' ‘Letters, Alphabetic, and Ideographic’ of the Unicode ' - 'Standard.\n' - '\n' - 'str.isascii()\n' - '\n' - ' Return "True" if the string is empty or all characters ' - 'in the\n' - ' string are ASCII, "False" otherwise. ASCII characters ' - 'have code\n' - ' points in the range U+0000-U+007F.\n' - '\n' - ' Added in version 3.7.\n' - '\n' - 'str.isdecimal()\n' - '\n' - ' Return "True" if all characters in the string are ' - 'decimal\n' - ' characters and there is at least one character, "False" ' - 'otherwise.\n' - ' Decimal characters are those that can be used to form ' - 'numbers in\n' - ' base 10, e.g. U+0660, ARABIC-INDIC DIGIT ZERO. ' - 'Formally a decimal\n' - ' character is a character in the Unicode General ' - 'Category “Nd”.\n' - '\n' - 'str.isdigit()\n' - '\n' - ' Return "True" if all characters in the string are ' - 'digits and there\n' - ' is at least one character, "False" otherwise. Digits ' - 'include\n' - ' decimal characters and digits that need special ' - 'handling, such as\n' - ' the compatibility superscript digits. This covers ' - 'digits which\n' - ' cannot be used to form numbers in base 10, like the ' - 'Kharosthi\n' - ' numbers. Formally, a digit is a character that has the ' - 'property\n' - ' value Numeric_Type=Digit or Numeric_Type=Decimal.\n' - '\n' - 'str.isidentifier()\n' - '\n' - ' Return "True" if the string is a valid identifier ' - 'according to the\n' - ' language definition, section Identifiers and keywords.\n' - '\n' - ' "keyword.iskeyword()" can be used to test whether ' - 'string "s" is a\n' - ' reserved identifier, such as "def" and "class".\n' - '\n' - ' Example:\n' - '\n' - ' >>> from keyword import iskeyword\n' - '\n' - " >>> 'hello'.isidentifier(), iskeyword('hello')\n" - ' (True, False)\n' - " >>> 'def'.isidentifier(), iskeyword('def')\n" - ' (True, True)\n' - '\n' - 'str.islower()\n' - '\n' - ' Return "True" if all cased characters [4] in the string ' - 'are\n' - ' lowercase and there is at least one cased character, ' - '"False"\n' - ' otherwise.\n' - '\n' - 'str.isnumeric()\n' - '\n' - ' Return "True" if all characters in the string are ' - 'numeric\n' - ' characters, and there is at least one character, ' - '"False" otherwise.\n' - ' Numeric characters include digit characters, and all ' - 'characters\n' - ' that have the Unicode numeric value property, e.g. ' - 'U+2155, VULGAR\n' - ' FRACTION ONE FIFTH. Formally, numeric characters are ' - 'those with\n' - ' the property value Numeric_Type=Digit, ' - 'Numeric_Type=Decimal or\n' - ' Numeric_Type=Numeric.\n' - '\n' - 'str.isprintable()\n' - '\n' - ' Return "True" if all characters in the string are ' - 'printable or the\n' - ' string is empty, "False" otherwise. Nonprintable ' - 'characters are\n' - ' those characters defined in the Unicode character ' - 'database as\n' - ' “Other” or “Separator”, excepting the ASCII space ' - '(0x20) which is\n' - ' considered printable. (Note that printable characters ' - 'in this\n' - ' context are those which should not be escaped when ' - '"repr()" is\n' - ' invoked on a string. It has no bearing on the handling ' - 'of strings\n' - ' written to "sys.stdout" or "sys.stderr".)\n' - '\n' - 'str.isspace()\n' - '\n' - ' Return "True" if there are only whitespace characters ' - 'in the string\n' - ' and there is at least one character, "False" ' - 'otherwise.\n' - '\n' - ' A character is *whitespace* if in the Unicode character ' - 'database\n' - ' (see "unicodedata"), either its general category is ' - '"Zs"\n' - ' (“Separator, space”), or its bidirectional class is one ' - 'of "WS",\n' - ' "B", or "S".\n' - '\n' - 'str.istitle()\n' - '\n' - ' Return "True" if the string is a titlecased string and ' - 'there is at\n' - ' least one character, for example uppercase characters ' - 'may only\n' - ' follow uncased characters and lowercase characters only ' - 'cased ones.\n' - ' Return "False" otherwise.\n' - '\n' - 'str.isupper()\n' - '\n' - ' Return "True" if all cased characters [4] in the string ' - 'are\n' - ' uppercase and there is at least one cased character, ' - '"False"\n' - ' otherwise.\n' - '\n' - " >>> 'BANANA'.isupper()\n" - ' True\n' - " >>> 'banana'.isupper()\n" - ' False\n' - " >>> 'baNana'.isupper()\n" - ' False\n' - " >>> ' '.isupper()\n" - ' False\n' - '\n' - 'str.join(iterable)\n' - '\n' - ' Return a string which is the concatenation of the ' - 'strings in\n' - ' *iterable*. A "TypeError" will be raised if there are ' - 'any non-\n' - ' string values in *iterable*, including "bytes" ' - 'objects. The\n' - ' separator between elements is the string providing this ' - 'method.\n' - '\n' - 'str.ljust(width[, fillchar])\n' - '\n' - ' Return the string left justified in a string of length ' - '*width*.\n' - ' Padding is done using the specified *fillchar* (default ' - 'is an ASCII\n' - ' space). The original string is returned if *width* is ' - 'less than or\n' - ' equal to "len(s)".\n' - '\n' - 'str.lower()\n' - '\n' - ' Return a copy of the string with all the cased ' - 'characters [4]\n' - ' converted to lowercase.\n' - '\n' - ' The lowercasing algorithm used is described in section ' - '3.13\n' - ' ‘Default Case Folding’ of the Unicode Standard.\n' - '\n' - 'str.lstrip([chars])\n' - '\n' - ' Return a copy of the string with leading characters ' - 'removed. The\n' - ' *chars* argument is a string specifying the set of ' - 'characters to be\n' - ' removed. If omitted or "None", the *chars* argument ' - 'defaults to\n' - ' removing whitespace. The *chars* argument is not a ' - 'prefix; rather,\n' - ' all combinations of its values are stripped:\n' - '\n' - " >>> ' spacious '.lstrip()\n" - " 'spacious '\n" - " >>> 'www.example.com'.lstrip('cmowz.')\n" - " 'example.com'\n" - '\n' - ' See "str.removeprefix()" for a method that will remove ' - 'a single\n' - ' prefix string rather than all of a set of characters. ' - 'For example:\n' - '\n' - " >>> 'Arthur: three!'.lstrip('Arthur: ')\n" - " 'ee!'\n" - " >>> 'Arthur: three!'.removeprefix('Arthur: ')\n" - " 'three!'\n" - '\n' - 'static str.maketrans(x[, y[, z]])\n' - '\n' - ' This static method returns a translation table usable ' - 'for\n' - ' "str.translate()".\n' - '\n' - ' If there is only one argument, it must be a dictionary ' - 'mapping\n' - ' Unicode ordinals (integers) or characters (strings of ' - 'length 1) to\n' - ' Unicode ordinals, strings (of arbitrary lengths) or ' - '"None".\n' - ' Character keys will then be converted to ordinals.\n' - '\n' - ' If there are two arguments, they must be strings of ' - 'equal length,\n' - ' and in the resulting dictionary, each character in x ' - 'will be mapped\n' - ' to the character at the same position in y. If there ' - 'is a third\n' - ' argument, it must be a string, whose characters will be ' - 'mapped to\n' - ' "None" in the result.\n' - '\n' - 'str.partition(sep)\n' - '\n' - ' Split the string at the first occurrence of *sep*, and ' - 'return a\n' - ' 3-tuple containing the part before the separator, the ' - 'separator\n' - ' itself, and the part after the separator. If the ' - 'separator is not\n' - ' found, return a 3-tuple containing the string itself, ' - 'followed by\n' - ' two empty strings.\n' - '\n' - 'str.removeprefix(prefix, /)\n' - '\n' - ' If the string starts with the *prefix* string, return\n' - ' "string[len(prefix):]". Otherwise, return a copy of the ' - 'original\n' - ' string:\n' - '\n' - " >>> 'TestHook'.removeprefix('Test')\n" - " 'Hook'\n" - " >>> 'BaseTestCase'.removeprefix('Test')\n" - " 'BaseTestCase'\n" - '\n' - ' Added in version 3.9.\n' - '\n' - 'str.removesuffix(suffix, /)\n' - '\n' - ' If the string ends with the *suffix* string and that ' - '*suffix* is\n' - ' not empty, return "string[:-len(suffix)]". Otherwise, ' - 'return a copy\n' - ' of the original string:\n' - '\n' - " >>> 'MiscTests'.removesuffix('Tests')\n" - " 'Misc'\n" - " >>> 'TmpDirMixin'.removesuffix('Tests')\n" - " 'TmpDirMixin'\n" - '\n' - ' Added in version 3.9.\n' - '\n' - 'str.replace(old, new, count=-1)\n' - '\n' - ' Return a copy of the string with all occurrences of ' - 'substring *old*\n' - ' replaced by *new*. If *count* is given, only the first ' - '*count*\n' - ' occurrences are replaced. If *count* is not specified ' - 'or "-1", then\n' - ' all occurrences are replaced.\n' - '\n' - ' Changed in version 3.13: *count* is now supported as a ' - 'keyword\n' - ' argument.\n' - '\n' - 'str.rfind(sub[, start[, end]])\n' - '\n' - ' Return the highest index in the string where substring ' - '*sub* is\n' - ' found, such that *sub* is contained within ' - '"s[start:end]".\n' - ' Optional arguments *start* and *end* are interpreted as ' - 'in slice\n' - ' notation. Return "-1" on failure.\n' - '\n' - 'str.rindex(sub[, start[, end]])\n' - '\n' - ' Like "rfind()" but raises "ValueError" when the ' - 'substring *sub* is\n' - ' not found.\n' - '\n' - 'str.rjust(width[, fillchar])\n' - '\n' - ' Return the string right justified in a string of length ' - '*width*.\n' - ' Padding is done using the specified *fillchar* (default ' - 'is an ASCII\n' - ' space). The original string is returned if *width* is ' - 'less than or\n' - ' equal to "len(s)".\n' - '\n' - 'str.rpartition(sep)\n' - '\n' - ' Split the string at the last occurrence of *sep*, and ' - 'return a\n' - ' 3-tuple containing the part before the separator, the ' - 'separator\n' - ' itself, and the part after the separator. If the ' - 'separator is not\n' - ' found, return a 3-tuple containing two empty strings, ' - 'followed by\n' - ' the string itself.\n' - '\n' - 'str.rsplit(sep=None, maxsplit=-1)\n' - '\n' - ' Return a list of the words in the string, using *sep* ' - 'as the\n' - ' delimiter string. If *maxsplit* is given, at most ' - '*maxsplit* splits\n' - ' are done, the *rightmost* ones. If *sep* is not ' - 'specified or\n' - ' "None", any whitespace string is a separator. Except ' - 'for splitting\n' - ' from the right, "rsplit()" behaves like "split()" which ' - 'is\n' - ' described in detail below.\n' - '\n' - 'str.rstrip([chars])\n' - '\n' - ' Return a copy of the string with trailing characters ' - 'removed. The\n' - ' *chars* argument is a string specifying the set of ' - 'characters to be\n' - ' removed. If omitted or "None", the *chars* argument ' - 'defaults to\n' - ' removing whitespace. The *chars* argument is not a ' - 'suffix; rather,\n' - ' all combinations of its values are stripped:\n' - '\n' - " >>> ' spacious '.rstrip()\n" - " ' spacious'\n" - " >>> 'mississippi'.rstrip('ipz')\n" - " 'mississ'\n" - '\n' - ' See "str.removesuffix()" for a method that will remove ' - 'a single\n' - ' suffix string rather than all of a set of characters. ' - 'For example:\n' - '\n' - " >>> 'Monty Python'.rstrip(' Python')\n" - " 'M'\n" - " >>> 'Monty Python'.removesuffix(' Python')\n" - " 'Monty'\n" - '\n' - 'str.split(sep=None, maxsplit=-1)\n' - '\n' - ' Return a list of the words in the string, using *sep* ' - 'as the\n' - ' delimiter string. If *maxsplit* is given, at most ' - '*maxsplit*\n' - ' splits are done (thus, the list will have at most ' - '"maxsplit+1"\n' - ' elements). If *maxsplit* is not specified or "-1", ' - 'then there is\n' - ' no limit on the number of splits (all possible splits ' - 'are made).\n' - '\n' - ' If *sep* is given, consecutive delimiters are not ' - 'grouped together\n' - ' and are deemed to delimit empty strings (for example,\n' - ' "\'1,,2\'.split(\',\')" returns "[\'1\', \'\', ' - '\'2\']"). The *sep* argument\n' - ' may consist of multiple characters as a single ' - 'delimiter (to split\n' - ' with multiple delimiters, use "re.split()"). Splitting ' - 'an empty\n' - ' string with a specified separator returns "[\'\']".\n' - '\n' - ' For example:\n' - '\n' - " >>> '1,2,3'.split(',')\n" - " ['1', '2', '3']\n" - " >>> '1,2,3'.split(',', maxsplit=1)\n" - " ['1', '2,3']\n" - " >>> '1,2,,3,'.split(',')\n" - " ['1', '2', '', '3', '']\n" - " >>> '1<>2<>3<4'.split('<>')\n" - " ['1', '2', '3<4']\n" - '\n' - ' If *sep* is not specified or is "None", a different ' - 'splitting\n' - ' algorithm is applied: runs of consecutive whitespace ' - 'are regarded\n' - ' as a single separator, and the result will contain no ' - 'empty strings\n' - ' at the start or end if the string has leading or ' - 'trailing\n' - ' whitespace. Consequently, splitting an empty string or ' - 'a string\n' - ' consisting of just whitespace with a "None" separator ' - 'returns "[]".\n' - '\n' - ' For example:\n' - '\n' - " >>> '1 2 3'.split()\n" - " ['1', '2', '3']\n" - " >>> '1 2 3'.split(maxsplit=1)\n" - " ['1', '2 3']\n" - " >>> ' 1 2 3 '.split()\n" - " ['1', '2', '3']\n" - '\n' - 'str.splitlines(keepends=False)\n' - '\n' - ' Return a list of the lines in the string, breaking at ' - 'line\n' - ' boundaries. Line breaks are not included in the ' - 'resulting list\n' - ' unless *keepends* is given and true.\n' - '\n' - ' This method splits on the following line boundaries. ' - 'In\n' - ' particular, the boundaries are a superset of *universal ' - 'newlines*.\n' - '\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | Representation | ' - 'Description |\n' - ' ' - '|=========================|===============================|\n' - ' | "\\n" | Line ' - 'Feed |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\r" | Carriage ' - 'Return |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\r\\n" | Carriage Return + Line ' - 'Feed |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\v" or "\\x0b" | Line ' - 'Tabulation |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\f" or "\\x0c" | Form ' - 'Feed |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\x1c" | File ' - 'Separator |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\x1d" | Group ' - 'Separator |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\x1e" | Record ' - 'Separator |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\x85" | Next Line (C1 Control ' - 'Code) |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\u2028" | Line ' - 'Separator |\n' - ' ' - '+-------------------------+-------------------------------+\n' - ' | "\\u2029" | Paragraph ' - 'Separator |\n' - ' ' - '+-------------------------+-------------------------------+\n' - '\n' - ' Changed in version 3.2: "\\v" and "\\f" added to list ' - 'of line\n' - ' boundaries.\n' - '\n' - ' For example:\n' - '\n' - " >>> 'ab c\\n\\nde fg\\rkl\\r\\n'.splitlines()\n" - " ['ab c', '', 'de fg', 'kl']\n" - " >>> 'ab c\\n\\nde " - "fg\\rkl\\r\\n'.splitlines(keepends=True)\n" - " ['ab c\\n', '\\n', 'de fg\\r', 'kl\\r\\n']\n" - '\n' - ' Unlike "split()" when a delimiter string *sep* is ' - 'given, this\n' - ' method returns an empty list for the empty string, and ' - 'a terminal\n' - ' line break does not result in an extra line:\n' - '\n' - ' >>> "".splitlines()\n' - ' []\n' - ' >>> "One line\\n".splitlines()\n' - " ['One line']\n" - '\n' - ' For comparison, "split(\'\\n\')" gives:\n' - '\n' - " >>> ''.split('\\n')\n" - " ['']\n" - " >>> 'Two lines\\n'.split('\\n')\n" - " ['Two lines', '']\n" - '\n' - 'str.startswith(prefix[, start[, end]])\n' - '\n' - ' Return "True" if string starts with the *prefix*, ' - 'otherwise return\n' - ' "False". *prefix* can also be a tuple of prefixes to ' - 'look for.\n' - ' With optional *start*, test string beginning at that ' - 'position.\n' - ' With optional *end*, stop comparing string at that ' - 'position.\n' - '\n' - 'str.strip([chars])\n' - '\n' - ' Return a copy of the string with the leading and ' - 'trailing\n' - ' characters removed. The *chars* argument is a string ' - 'specifying the\n' - ' set of characters to be removed. If omitted or "None", ' - 'the *chars*\n' - ' argument defaults to removing whitespace. The *chars* ' - 'argument is\n' - ' not a prefix or suffix; rather, all combinations of its ' - 'values are\n' - ' stripped:\n' - '\n' - " >>> ' spacious '.strip()\n" - " 'spacious'\n" - " >>> 'www.example.com'.strip('cmowz.')\n" - " 'example'\n" - '\n' - ' The outermost leading and trailing *chars* argument ' - 'values are\n' - ' stripped from the string. Characters are removed from ' - 'the leading\n' - ' end until reaching a string character that is not ' - 'contained in the\n' - ' set of characters in *chars*. A similar action takes ' - 'place on the\n' - ' trailing end. For example:\n' - '\n' - " >>> comment_string = '#....... Section 3.2.1 Issue " - "#32 .......'\n" - " >>> comment_string.strip('.#! ')\n" - " 'Section 3.2.1 Issue #32'\n" - '\n' - 'str.swapcase()\n' - '\n' - ' Return a copy of the string with uppercase characters ' - 'converted to\n' - ' lowercase and vice versa. Note that it is not ' - 'necessarily true that\n' - ' "s.swapcase().swapcase() == s".\n' - '\n' - 'str.title()\n' - '\n' - ' Return a titlecased version of the string where words ' - 'start with an\n' - ' uppercase character and the remaining characters are ' - 'lowercase.\n' - '\n' - ' For example:\n' - '\n' - " >>> 'Hello world'.title()\n" - " 'Hello World'\n" - '\n' - ' The algorithm uses a simple language-independent ' - 'definition of a\n' - ' word as groups of consecutive letters. The definition ' - 'works in\n' - ' many contexts but it means that apostrophes in ' - 'contractions and\n' - ' possessives form word boundaries, which may not be the ' - 'desired\n' - ' result:\n' - '\n' - ' >>> "they\'re bill\'s friends from the UK".title()\n' - ' "They\'Re Bill\'S Friends From The Uk"\n' - '\n' - ' The "string.capwords()" function does not have this ' - 'problem, as it\n' - ' splits words on spaces only.\n' - '\n' - ' Alternatively, a workaround for apostrophes can be ' - 'constructed\n' - ' using regular expressions:\n' - '\n' - ' >>> import re\n' - ' >>> def titlecase(s):\n' - ' ... return re.sub(r"[A-Za-z]+(\'[A-Za-z]+)?",\n' - ' ... lambda mo: ' - 'mo.group(0).capitalize(),\n' - ' ... s)\n' - ' ...\n' - ' >>> titlecase("they\'re bill\'s friends.")\n' - ' "They\'re Bill\'s Friends."\n' - '\n' - 'str.translate(table)\n' - '\n' - ' Return a copy of the string in which each character has ' - 'been mapped\n' - ' through the given translation table. The table must be ' - 'an object\n' - ' that implements indexing via "__getitem__()", typically ' - 'a *mapping*\n' - ' or *sequence*. When indexed by a Unicode ordinal (an ' - 'integer), the\n' - ' table object can do any of the following: return a ' - 'Unicode ordinal\n' - ' or a string, to map the character to one or more other ' - 'characters;\n' - ' return "None", to delete the character from the return ' - 'string; or\n' - ' raise a "LookupError" exception, to map the character ' - 'to itself.\n' - '\n' - ' You can use "str.maketrans()" to create a translation ' - 'map from\n' - ' character-to-character mappings in different formats.\n' - '\n' - ' See also the "codecs" module for a more flexible ' - 'approach to custom\n' - ' character mappings.\n' - '\n' - 'str.upper()\n' - '\n' - ' Return a copy of the string with all the cased ' - 'characters [4]\n' - ' converted to uppercase. Note that ' - '"s.upper().isupper()" might be\n' - ' "False" if "s" contains uncased characters or if the ' - 'Unicode\n' - ' category of the resulting character(s) is not “Lu” ' - '(Letter,\n' - ' uppercase), but e.g. “Lt” (Letter, titlecase).\n' - '\n' - ' The uppercasing algorithm used is described in section ' - '3.13\n' - ' ‘Default Case Folding’ of the Unicode Standard.\n' - '\n' - 'str.zfill(width)\n' - '\n' - ' Return a copy of the string left filled with ASCII ' - '"\'0\'" digits to\n' - ' make a string of length *width*. A leading sign prefix\n' - ' ("\'+\'"/"\'-\'") is handled by inserting the padding ' - '*after* the sign\n' - ' character rather than before. The original string is ' - 'returned if\n' - ' *width* is less than or equal to "len(s)".\n' - '\n' - ' For example:\n' - '\n' - ' >>> "42".zfill(5)\n' - " '00042'\n" - ' >>> "-42".zfill(5)\n' - " '-0042'\n", - 'strings': 'String and Bytes literals\n' - '*************************\n' - '\n' - 'String literals are described by the following lexical ' - 'definitions:\n' - '\n' - ' stringliteral ::= [stringprefix](shortstring | longstring)\n' - ' stringprefix ::= "r" | "u" | "R" | "U" | "f" | "F"\n' - ' | "fr" | "Fr" | "fR" | "FR" | "rf" | "rF" | ' - '"Rf" | "RF"\n' - ' shortstring ::= "\'" shortstringitem* "\'" | \'"\' ' - 'shortstringitem* \'"\'\n' - ' longstring ::= "\'\'\'" longstringitem* "\'\'\'" | ' - '\'"""\' longstringitem* \'"""\'\n' - ' shortstringitem ::= shortstringchar | stringescapeseq\n' - ' longstringitem ::= longstringchar | stringescapeseq\n' - ' shortstringchar ::= <any source character except "\\" or ' - 'newline or the quote>\n' - ' longstringchar ::= <any source character except "\\">\n' - ' stringescapeseq ::= "\\" <any source character>\n' - '\n' - ' bytesliteral ::= bytesprefix(shortbytes | longbytes)\n' - ' bytesprefix ::= "b" | "B" | "br" | "Br" | "bR" | "BR" | ' - '"rb" | "rB" | "Rb" | "RB"\n' - ' shortbytes ::= "\'" shortbytesitem* "\'" | \'"\' ' - 'shortbytesitem* \'"\'\n' - ' longbytes ::= "\'\'\'" longbytesitem* "\'\'\'" | \'"""\' ' - 'longbytesitem* \'"""\'\n' - ' shortbytesitem ::= shortbyteschar | bytesescapeseq\n' - ' longbytesitem ::= longbyteschar | bytesescapeseq\n' - ' shortbyteschar ::= <any ASCII character except "\\" or newline ' - 'or the quote>\n' - ' longbyteschar ::= <any ASCII character except "\\">\n' - ' bytesescapeseq ::= "\\" <any ASCII character>\n' - '\n' - 'One syntactic restriction not indicated by these productions is ' - 'that\n' - 'whitespace is not allowed between the "stringprefix" or ' - '"bytesprefix"\n' - 'and the rest of the literal. The source character set is defined ' - 'by\n' - 'the encoding declaration; it is UTF-8 if no encoding declaration ' - 'is\n' - 'given in the source file; see section Encoding declarations.\n' - '\n' - 'In plain English: Both types of literals can be enclosed in ' - 'matching\n' - 'single quotes ("\'") or double quotes ("""). They can also be ' - 'enclosed\n' - 'in matching groups of three single or double quotes (these are\n' - 'generally referred to as *triple-quoted strings*). The backslash ' - '("\\")\n' - 'character is used to give special meaning to otherwise ordinary\n' - 'characters like "n", which means ‘newline’ when escaped ("\\n"). ' - 'It can\n' - 'also be used to escape characters that otherwise have a special\n' - 'meaning, such as newline, backslash itself, or the quote ' - 'character.\n' - 'See escape sequences below for examples.\n' - '\n' - 'Bytes literals are always prefixed with "\'b\'" or "\'B\'"; they ' - 'produce\n' - 'an instance of the "bytes" type instead of the "str" type. They ' - 'may\n' - 'only contain ASCII characters; bytes with a numeric value of 128 ' - 'or\n' - 'greater must be expressed with escapes.\n' - '\n' - 'Both string and bytes literals may optionally be prefixed with a\n' - 'letter "\'r\'" or "\'R\'"; such constructs are called *raw ' - 'string\n' - 'literals* and *raw bytes literals* respectively and treat ' - 'backslashes\n' - 'as literal characters. As a result, in raw string literals, ' - '"\'\\U\'"\n' - 'and "\'\\u\'" escapes are not treated specially.\n' - '\n' - 'Added in version 3.3: The "\'rb\'" prefix of raw bytes literals ' - 'has been\n' - 'added as a synonym of "\'br\'".Support for the unicode legacy ' - 'literal\n' - '("u\'value\'") was reintroduced to simplify the maintenance of ' - 'dual\n' - 'Python 2.x and 3.x codebases. See **PEP 414** for more ' - 'information.\n' - '\n' - 'A string literal with "\'f\'" or "\'F\'" in its prefix is a ' - '*formatted\n' - 'string literal*; see f-strings. The "\'f\'" may be combined with ' - '"\'r\'",\n' - 'but not with "\'b\'" or "\'u\'", therefore raw formatted strings ' - 'are\n' - 'possible, but formatted bytes literals are not.\n' - '\n' - 'In triple-quoted literals, unescaped newlines and quotes are ' - 'allowed\n' - '(and are retained), except that three unescaped quotes in a row\n' - 'terminate the literal. (A “quote” is the character used to open ' - 'the\n' - 'literal, i.e. either "\'" or """.)\n' - '\n' - '\n' - 'Escape sequences\n' - '================\n' - '\n' - 'Unless an "\'r\'" or "\'R\'" prefix is present, escape sequences ' - 'in string\n' - 'and bytes literals are interpreted according to rules similar to ' - 'those\n' - 'used by Standard C. The recognized escape sequences are:\n' - '\n' - '+---------------------------+-----------------------------------+---------+\n' - '| Escape Sequence | Meaning | ' - 'Notes |\n' - '|===========================|===================================|=========|\n' - '| "\\"<newline> | Backslash and newline ignored ' - '| (1) |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\\\" | Backslash ' - '("\\") | |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\\'" | Single quote ' - '("\'") | |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\"" | Double quote (""") ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\a" | ASCII Bell (BEL) ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\b" | ASCII Backspace (BS) ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\f" | ASCII Formfeed (FF) ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\n" | ASCII Linefeed (LF) ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\r" | ASCII Carriage Return (CR) ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\t" | ASCII Horizontal Tab (TAB) ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\v" | ASCII Vertical Tab (VT) ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\*ooo*" | Character with octal value *ooo* ' - '| (2,4) |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\x*hh*" | Character with hex value *hh* ' - '| (3,4) |\n' - '+---------------------------+-----------------------------------+---------+\n' - '\n' - 'Escape sequences only recognized in string literals are:\n' - '\n' - '+---------------------------+-----------------------------------+---------+\n' - '| Escape Sequence | Meaning | ' - 'Notes |\n' - '|===========================|===================================|=========|\n' - '| "\\N{*name*}" | Character named *name* in the ' - '| (5) |\n' - '| | Unicode database ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\u*xxxx*" | Character with 16-bit hex value ' - '| (6) |\n' - '| | *xxxx* ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '| "\\U*xxxxxxxx*" | Character with 32-bit hex value ' - '| (7) |\n' - '| | *xxxxxxxx* ' - '| |\n' - '+---------------------------+-----------------------------------+---------+\n' - '\n' - 'Notes:\n' - '\n' - '1. A backslash can be added at the end of a line to ignore the\n' - ' newline:\n' - '\n' - " >>> 'This string will not include \\\n" - " ... backslashes or newline characters.'\n" - " 'This string will not include backslashes or newline " - "characters.'\n" - '\n' - ' The same result can be achieved using triple-quoted strings, ' - 'or\n' - ' parentheses and string literal concatenation.\n' - '\n' - '2. As in Standard C, up to three octal digits are accepted.\n' - '\n' - ' Changed in version 3.11: Octal escapes with value larger than\n' - ' "0o377" produce a "DeprecationWarning".\n' - '\n' - ' Changed in version 3.12: Octal escapes with value larger than\n' - ' "0o377" produce a "SyntaxWarning". In a future Python version ' - 'they\n' - ' will be eventually a "SyntaxError".\n' - '\n' - '3. Unlike in Standard C, exactly two hex digits are required.\n' - '\n' - '4. In a bytes literal, hexadecimal and octal escapes denote the ' - 'byte\n' - ' with the given value. In a string literal, these escapes ' - 'denote a\n' - ' Unicode character with the given value.\n' - '\n' - '5. Changed in version 3.3: Support for name aliases [1] has been\n' - ' added.\n' - '\n' - '6. Exactly four hex digits are required.\n' - '\n' - '7. Any Unicode character can be encoded this way. Exactly eight ' - 'hex\n' - ' digits are required.\n' - '\n' - 'Unlike Standard C, all unrecognized escape sequences are left in ' - 'the\n' - 'string unchanged, i.e., *the backslash is left in the result*. ' - '(This\n' - 'behavior is useful when debugging: if an escape sequence is ' - 'mistyped,\n' - 'the resulting output is more easily recognized as broken.) It is ' - 'also\n' - 'important to note that the escape sequences only recognized in ' - 'string\n' - 'literals fall into the category of unrecognized escapes for ' - 'bytes\n' - 'literals.\n' - '\n' - 'Changed in version 3.6: Unrecognized escape sequences produce a\n' - '"DeprecationWarning".\n' - '\n' - 'Changed in version 3.12: Unrecognized escape sequences produce a\n' - '"SyntaxWarning". In a future Python version they will be ' - 'eventually a\n' - '"SyntaxError".\n' - '\n' - 'Even in a raw literal, quotes can be escaped with a backslash, ' - 'but the\n' - 'backslash remains in the result; for example, "r"\\""" is a ' - 'valid\n' - 'string literal consisting of two characters: a backslash and a ' - 'double\n' - 'quote; "r"\\"" is not a valid string literal (even a raw string ' - 'cannot\n' - 'end in an odd number of backslashes). Specifically, *a raw ' - 'literal\n' - 'cannot end in a single backslash* (since the backslash would ' - 'escape\n' - 'the following quote character). Note also that a single ' - 'backslash\n' - 'followed by a newline is interpreted as those two characters as ' - 'part\n' - 'of the literal, *not* as a line continuation.\n', - 'subscriptions': 'Subscriptions\n' - '*************\n' - '\n' - 'The subscription of an instance of a container class will ' - 'generally\n' - 'select an element from the container. The subscription of a ' - '*generic\n' - 'class* will generally return a GenericAlias object.\n' - '\n' - ' subscription ::= primary "[" flexible_expression_list ' - '"]"\n' - '\n' - 'When an object is subscripted, the interpreter will ' - 'evaluate the\n' - 'primary and the expression list.\n' - '\n' - 'The primary must evaluate to an object that supports ' - 'subscription. An\n' - 'object may support subscription through defining one or ' - 'both of\n' - '"__getitem__()" and "__class_getitem__()". When the primary ' - 'is\n' - 'subscripted, the evaluated result of the expression list ' - 'will be\n' - 'passed to one of these methods. For more details on when\n' - '"__class_getitem__" is called instead of "__getitem__", ' - 'see\n' - '__class_getitem__ versus __getitem__.\n' - '\n' - 'If the expression list contains at least one comma, or if ' - 'any of the\n' - 'expressions are starred, the expression list will evaluate ' - 'to a\n' - '"tuple" containing the items of the expression list. ' - 'Otherwise, the\n' - 'expression list will evaluate to the value of the list’s ' - 'sole member.\n' - '\n' - 'Changed in version 3.11: Expressions in an expression list ' - 'may be\n' - 'starred. See **PEP 646**.\n' - '\n' - 'For built-in objects, there are two types of objects that ' - 'support\n' - 'subscription via "__getitem__()":\n' - '\n' - '1. Mappings. If the primary is a *mapping*, the expression ' - 'list must\n' - ' evaluate to an object whose value is one of the keys of ' - 'the\n' - ' mapping, and the subscription selects the value in the ' - 'mapping that\n' - ' corresponds to that key. An example of a builtin mapping ' - 'class is\n' - ' the "dict" class.\n' - '\n' - '2. Sequences. If the primary is a *sequence*, the ' - 'expression list must\n' - ' evaluate to an "int" or a "slice" (as discussed in the ' - 'following\n' - ' section). Examples of builtin sequence classes include ' - 'the "str",\n' - ' "list" and "tuple" classes.\n' - '\n' - 'The formal syntax makes no special provision for negative ' - 'indices in\n' - '*sequences*. However, built-in sequences all provide a ' - '"__getitem__()"\n' - 'method that interprets negative indices by adding the ' - 'length of the\n' - 'sequence to the index so that, for example, "x[-1]" selects ' - 'the last\n' - 'item of "x". The resulting value must be a nonnegative ' - 'integer less\n' - 'than the number of items in the sequence, and the ' - 'subscription selects\n' - 'the item whose index is that value (counting from zero). ' - 'Since the\n' - 'support for negative indices and slicing occurs in the ' - 'object’s\n' - '"__getitem__()" method, subclasses overriding this method ' - 'will need to\n' - 'explicitly add that support.\n' - '\n' - 'A "string" is a special kind of sequence whose items are ' - '*characters*.\n' - 'A character is not a separate data type but a string of ' - 'exactly one\n' - 'character.\n', - 'truth': 'Truth Value Testing\n' - '*******************\n' - '\n' - 'Any object can be tested for truth value, for use in an "if" or\n' - '"while" condition or as operand of the Boolean operations below.\n' - '\n' - 'By default, an object is considered true unless its class defines\n' - 'either a "__bool__()" method that returns "False" or a "__len__()"\n' - 'method that returns zero, when called with the object. [1] Here ' - 'are\n' - 'most of the built-in objects considered false:\n' - '\n' - '* constants defined to be false: "None" and "False"\n' - '\n' - '* zero of any numeric type: "0", "0.0", "0j", "Decimal(0)",\n' - ' "Fraction(0, 1)"\n' - '\n' - '* empty sequences and collections: "\'\'", "()", "[]", "{}", ' - '"set()",\n' - ' "range(0)"\n' - '\n' - 'Operations and built-in functions that have a Boolean result ' - 'always\n' - 'return "0" or "False" for false and "1" or "True" for true, unless\n' - 'otherwise stated. (Important exception: the Boolean operations ' - '"or"\n' - 'and "and" always return one of their operands.)\n', - 'try': 'The "try" statement\n' - '*******************\n' - '\n' - 'The "try" statement specifies exception handlers and/or cleanup code\n' - 'for a group of statements:\n' - '\n' - ' try_stmt ::= try1_stmt | try2_stmt | try3_stmt\n' - ' try1_stmt ::= "try" ":" suite\n' - ' ("except" [expression ["as" identifier]] ":" ' - 'suite)+\n' - ' ["else" ":" suite]\n' - ' ["finally" ":" suite]\n' - ' try2_stmt ::= "try" ":" suite\n' - ' ("except" "*" expression ["as" identifier] ":" ' - 'suite)+\n' - ' ["else" ":" suite]\n' - ' ["finally" ":" suite]\n' - ' try3_stmt ::= "try" ":" suite\n' - ' "finally" ":" suite\n' - '\n' - 'Additional information on exceptions can be found in section\n' - 'Exceptions, and information on using the "raise" statement to ' - 'generate\n' - 'exceptions may be found in section The raise statement.\n' - '\n' - '\n' - '"except" clause\n' - '===============\n' - '\n' - 'The "except" clause(s) specify one or more exception handlers. When ' - 'no\n' - 'exception occurs in the "try" clause, no exception handler is\n' - 'executed. When an exception occurs in the "try" suite, a search for ' - 'an\n' - 'exception handler is started. This search inspects the "except"\n' - 'clauses in turn until one is found that matches the exception. An\n' - 'expression-less "except" clause, if present, must be last; it ' - 'matches\n' - 'any exception.\n' - '\n' - 'For an "except" clause with an expression, the expression must\n' - 'evaluate to an exception type or a tuple of exception types. The\n' - 'raised exception matches an "except" clause whose expression ' - 'evaluates\n' - 'to the class or a *non-virtual base class* of the exception object, ' - 'or\n' - 'to a tuple that contains such a class.\n' - '\n' - 'If no "except" clause matches the exception, the search for an\n' - 'exception handler continues in the surrounding code and on the\n' - 'invocation stack. [1]\n' - '\n' - 'If the evaluation of an expression in the header of an "except" ' - 'clause\n' - 'raises an exception, the original search for a handler is canceled ' - 'and\n' - 'a search starts for the new exception in the surrounding code and on\n' - 'the call stack (it is treated as if the entire "try" statement ' - 'raised\n' - 'the exception).\n' - '\n' - 'When a matching "except" clause is found, the exception is assigned ' - 'to\n' - 'the target specified after the "as" keyword in that "except" clause,\n' - 'if present, and the "except" clause’s suite is executed. All ' - '"except"\n' - 'clauses must have an executable block. When the end of this block is\n' - 'reached, execution continues normally after the entire "try"\n' - 'statement. (This means that if two nested handlers exist for the ' - 'same\n' - 'exception, and the exception occurs in the "try" clause of the inner\n' - 'handler, the outer handler will not handle the exception.)\n' - '\n' - 'When an exception has been assigned using "as target", it is cleared\n' - 'at the end of the "except" clause. This is as if\n' - '\n' - ' except E as N:\n' - ' foo\n' - '\n' - 'was translated to\n' - '\n' - ' except E as N:\n' - ' try:\n' - ' foo\n' - ' finally:\n' - ' del N\n' - '\n' - 'This means the exception must be assigned to a different name to be\n' - 'able to refer to it after the "except" clause. Exceptions are ' - 'cleared\n' - 'because with the traceback attached to them, they form a reference\n' - 'cycle with the stack frame, keeping all locals in that frame alive\n' - 'until the next garbage collection occurs.\n' - '\n' - 'Before an "except" clause’s suite is executed, the exception is ' - 'stored\n' - 'in the "sys" module, where it can be accessed from within the body ' - 'of\n' - 'the "except" clause by calling "sys.exception()". When leaving an\n' - 'exception handler, the exception stored in the "sys" module is reset\n' - 'to its previous value:\n' - '\n' - ' >>> print(sys.exception())\n' - ' None\n' - ' >>> try:\n' - ' ... raise TypeError\n' - ' ... except:\n' - ' ... print(repr(sys.exception()))\n' - ' ... try:\n' - ' ... raise ValueError\n' - ' ... except:\n' - ' ... print(repr(sys.exception()))\n' - ' ... print(repr(sys.exception()))\n' - ' ...\n' - ' TypeError()\n' - ' ValueError()\n' - ' TypeError()\n' - ' >>> print(sys.exception())\n' - ' None\n' - '\n' - '\n' - '"except*" clause\n' - '================\n' - '\n' - 'The "except*" clause(s) are used for handling "ExceptionGroup"s. The\n' - 'exception type for matching is interpreted as in the case of ' - '"except",\n' - 'but in the case of exception groups we can have partial matches when\n' - 'the type matches some of the exceptions in the group. This means ' - 'that\n' - 'multiple "except*" clauses can execute, each handling part of the\n' - 'exception group. Each clause executes at most once and handles an\n' - 'exception group of all matching exceptions. Each exception in the\n' - 'group is handled by at most one "except*" clause, the first that\n' - 'matches it.\n' - '\n' - ' >>> try:\n' - ' ... raise ExceptionGroup("eg",\n' - ' ... [ValueError(1), TypeError(2), OSError(3), ' - 'OSError(4)])\n' - ' ... except* TypeError as e:\n' - " ... print(f'caught {type(e)} with nested {e.exceptions}')\n" - ' ... except* OSError as e:\n' - " ... print(f'caught {type(e)} with nested {e.exceptions}')\n" - ' ...\n' - " caught <class 'ExceptionGroup'> with nested (TypeError(2),)\n" - " caught <class 'ExceptionGroup'> with nested (OSError(3), " - 'OSError(4))\n' - ' + Exception Group Traceback (most recent call last):\n' - ' | File "<stdin>", line 2, in <module>\n' - ' | ExceptionGroup: eg\n' - ' +-+---------------- 1 ----------------\n' - ' | ValueError: 1\n' - ' +------------------------------------\n' - '\n' - 'Any remaining exceptions that were not handled by any "except*" ' - 'clause\n' - 'are re-raised at the end, along with all exceptions that were raised\n' - 'from within the "except*" clauses. If this list contains more than ' - 'one\n' - 'exception to reraise, they are combined into an exception group.\n' - '\n' - 'If the raised exception is not an exception group and its type ' - 'matches\n' - 'one of the "except*" clauses, it is caught and wrapped by an ' - 'exception\n' - 'group with an empty message string.\n' - '\n' - ' >>> try:\n' - ' ... raise BlockingIOError\n' - ' ... except* BlockingIOError as e:\n' - ' ... print(repr(e))\n' - ' ...\n' - " ExceptionGroup('', (BlockingIOError()))\n" - '\n' - 'An "except*" clause must have a matching expression; it cannot be\n' - '"except*:". Furthermore, this expression cannot contain exception\n' - 'group types, because that would have ambiguous semantics.\n' - '\n' - 'It is not possible to mix "except" and "except*" in the same "try".\n' - '"break", "continue" and "return" cannot appear in an "except*" ' - 'clause.\n' - '\n' - '\n' - '"else" clause\n' - '=============\n' - '\n' - 'The optional "else" clause is executed if the control flow leaves ' - 'the\n' - '"try" suite, no exception was raised, and no "return", "continue", ' - 'or\n' - '"break" statement was executed. Exceptions in the "else" clause are\n' - 'not handled by the preceding "except" clauses.\n' - '\n' - '\n' - '"finally" clause\n' - '================\n' - '\n' - 'If "finally" is present, it specifies a ‘cleanup’ handler. The ' - '"try"\n' - 'clause is executed, including any "except" and "else" clauses. If ' - 'an\n' - 'exception occurs in any of the clauses and is not handled, the\n' - 'exception is temporarily saved. The "finally" clause is executed. ' - 'If\n' - 'there is a saved exception it is re-raised at the end of the ' - '"finally"\n' - 'clause. If the "finally" clause raises another exception, the saved\n' - 'exception is set as the context of the new exception. If the ' - '"finally"\n' - 'clause executes a "return", "break" or "continue" statement, the ' - 'saved\n' - 'exception is discarded:\n' - '\n' - ' >>> def f():\n' - ' ... try:\n' - ' ... 1/0\n' - ' ... finally:\n' - ' ... return 42\n' - ' ...\n' - ' >>> f()\n' - ' 42\n' - '\n' - 'The exception information is not available to the program during\n' - 'execution of the "finally" clause.\n' - '\n' - 'When a "return", "break" or "continue" statement is executed in the\n' - '"try" suite of a "try"…"finally" statement, the "finally" clause is\n' - 'also executed ‘on the way out.’\n' - '\n' - 'The return value of a function is determined by the last "return"\n' - 'statement executed. Since the "finally" clause always executes, a\n' - '"return" statement executed in the "finally" clause will always be ' - 'the\n' - 'last one executed:\n' - '\n' - ' >>> def foo():\n' - ' ... try:\n' - " ... return 'try'\n" - ' ... finally:\n' - " ... return 'finally'\n" - ' ...\n' - ' >>> foo()\n' - " 'finally'\n" - '\n' - 'Changed in version 3.8: Prior to Python 3.8, a "continue" statement\n' - 'was illegal in the "finally" clause due to a problem with the\n' - 'implementation.\n', - 'types': 'The standard type hierarchy\n' - '***************************\n' - '\n' - 'Below is a list of the types that are built into Python. ' - 'Extension\n' - 'modules (written in C, Java, or other languages, depending on the\n' - 'implementation) can define additional types. Future versions of\n' - 'Python may add types to the type hierarchy (e.g., rational ' - 'numbers,\n' - 'efficiently stored arrays of integers, etc.), although such ' - 'additions\n' - 'will often be provided via the standard library instead.\n' - '\n' - 'Some of the type descriptions below contain a paragraph listing\n' - '‘special attributes.’ These are attributes that provide access to ' - 'the\n' - 'implementation and are not intended for general use. Their ' - 'definition\n' - 'may change in the future.\n' - '\n' - '\n' - 'None\n' - '====\n' - '\n' - 'This type has a single value. There is a single object with this\n' - 'value. This object is accessed through the built-in name "None". It ' - 'is\n' - 'used to signify the absence of a value in many situations, e.g., it ' - 'is\n' - 'returned from functions that don’t explicitly return anything. Its\n' - 'truth value is false.\n' - '\n' - '\n' - 'NotImplemented\n' - '==============\n' - '\n' - 'This type has a single value. There is a single object with this\n' - 'value. This object is accessed through the built-in name\n' - '"NotImplemented". Numeric methods and rich comparison methods ' - 'should\n' - 'return this value if they do not implement the operation for the\n' - 'operands provided. (The interpreter will then try the reflected\n' - 'operation, or some other fallback, depending on the operator.) It\n' - 'should not be evaluated in a boolean context.\n' - '\n' - 'See Implementing the arithmetic operations for more details.\n' - '\n' - 'Changed in version 3.9: Evaluating "NotImplemented" in a boolean\n' - 'context was deprecated.\n' - '\n' - 'Changed in version 3.14: Evaluating "NotImplemented" in a boolean\n' - 'context now raises a "TypeError". It previously evaluated to ' - '"True"\n' - 'and emitted a "DeprecationWarning" since Python 3.9.\n' - '\n' - '\n' - 'Ellipsis\n' - '========\n' - '\n' - 'This type has a single value. There is a single object with this\n' - 'value. This object is accessed through the literal "..." or the ' - 'built-\n' - 'in name "Ellipsis". Its truth value is true.\n' - '\n' - '\n' - '"numbers.Number"\n' - '================\n' - '\n' - 'These are created by numeric literals and returned as results by\n' - 'arithmetic operators and arithmetic built-in functions. Numeric\n' - 'objects are immutable; once created their value never changes. ' - 'Python\n' - 'numbers are of course strongly related to mathematical numbers, ' - 'but\n' - 'subject to the limitations of numerical representation in ' - 'computers.\n' - '\n' - 'The string representations of the numeric classes, computed by\n' - '"__repr__()" and "__str__()", have the following properties:\n' - '\n' - '* They are valid numeric literals which, when passed to their ' - 'class\n' - ' constructor, produce an object having the value of the original\n' - ' numeric.\n' - '\n' - '* The representation is in base 10, when possible.\n' - '\n' - '* Leading zeros, possibly excepting a single zero before a decimal\n' - ' point, are not shown.\n' - '\n' - '* Trailing zeros, possibly excepting a single zero after a decimal\n' - ' point, are not shown.\n' - '\n' - '* A sign is shown only when the number is negative.\n' - '\n' - 'Python distinguishes between integers, floating-point numbers, and\n' - 'complex numbers:\n' - '\n' - '\n' - '"numbers.Integral"\n' - '------------------\n' - '\n' - 'These represent elements from the mathematical set of integers\n' - '(positive and negative).\n' - '\n' - 'Note:\n' - '\n' - ' The rules for integer representation are intended to give the ' - 'most\n' - ' meaningful interpretation of shift and mask operations involving\n' - ' negative integers.\n' - '\n' - 'There are two types of integers:\n' - '\n' - 'Integers ("int")\n' - ' These represent numbers in an unlimited range, subject to ' - 'available\n' - ' (virtual) memory only. For the purpose of shift and mask\n' - ' operations, a binary representation is assumed, and negative\n' - ' numbers are represented in a variant of 2’s complement which ' - 'gives\n' - ' the illusion of an infinite string of sign bits extending to ' - 'the\n' - ' left.\n' - '\n' - 'Booleans ("bool")\n' - ' These represent the truth values False and True. The two ' - 'objects\n' - ' representing the values "False" and "True" are the only Boolean\n' - ' objects. The Boolean type is a subtype of the integer type, and\n' - ' Boolean values behave like the values 0 and 1, respectively, in\n' - ' almost all contexts, the exception being that when converted to ' - 'a\n' - ' string, the strings ""False"" or ""True"" are returned,\n' - ' respectively.\n' - '\n' - '\n' - '"numbers.Real" ("float")\n' - '------------------------\n' - '\n' - 'These represent machine-level double precision floating-point ' - 'numbers.\n' - 'You are at the mercy of the underlying machine architecture (and C ' - 'or\n' - 'Java implementation) for the accepted range and handling of ' - 'overflow.\n' - 'Python does not support single-precision floating-point numbers; ' - 'the\n' - 'savings in processor and memory usage that are usually the reason ' - 'for\n' - 'using these are dwarfed by the overhead of using objects in Python, ' - 'so\n' - 'there is no reason to complicate the language with two kinds of\n' - 'floating-point numbers.\n' - '\n' - '\n' - '"numbers.Complex" ("complex")\n' - '-----------------------------\n' - '\n' - 'These represent complex numbers as a pair of machine-level double\n' - 'precision floating-point numbers. The same caveats apply as for\n' - 'floating-point numbers. The real and imaginary parts of a complex\n' - 'number "z" can be retrieved through the read-only attributes ' - '"z.real"\n' - 'and "z.imag".\n' - '\n' - '\n' - 'Sequences\n' - '=========\n' - '\n' - 'These represent finite ordered sets indexed by non-negative ' - 'numbers.\n' - 'The built-in function "len()" returns the number of items of a\n' - 'sequence. When the length of a sequence is *n*, the index set ' - 'contains\n' - 'the numbers 0, 1, …, *n*-1. Item *i* of sequence *a* is selected ' - 'by\n' - '"a[i]". Some sequences, including built-in sequences, interpret\n' - 'negative subscripts by adding the sequence length. For example,\n' - '"a[-2]" equals "a[n-2]", the second to last item of sequence a ' - 'with\n' - 'length "n".\n' - '\n' - 'Sequences also support slicing: "a[i:j]" selects all items with ' - 'index\n' - '*k* such that *i* "<=" *k* "<" *j*. When used as an expression, a\n' - 'slice is a sequence of the same type. The comment above about ' - 'negative\n' - 'indexes also applies to negative slice positions.\n' - '\n' - 'Some sequences also support “extended slicing” with a third “step”\n' - 'parameter: "a[i:j:k]" selects all items of *a* with index *x* where ' - '"x\n' - '= i + n*k", *n* ">=" "0" and *i* "<=" *x* "<" *j*.\n' - '\n' - 'Sequences are distinguished according to their mutability:\n' - '\n' - '\n' - 'Immutable sequences\n' - '-------------------\n' - '\n' - 'An object of an immutable sequence type cannot change once it is\n' - 'created. (If the object contains references to other objects, ' - 'these\n' - 'other objects may be mutable and may be changed; however, the\n' - 'collection of objects directly referenced by an immutable object\n' - 'cannot change.)\n' - '\n' - 'The following types are immutable sequences:\n' - '\n' - 'Strings\n' - ' A string is a sequence of values that represent Unicode code\n' - ' points. All the code points in the range "U+0000 - U+10FFFF" can ' - 'be\n' - ' represented in a string. Python doesn’t have a char type; ' - 'instead,\n' - ' every code point in the string is represented as a string ' - 'object\n' - ' with length "1". The built-in function "ord()" converts a code\n' - ' point from its string form to an integer in the range "0 - ' - '10FFFF";\n' - ' "chr()" converts an integer in the range "0 - 10FFFF" to the\n' - ' corresponding length "1" string object. "str.encode()" can be ' - 'used\n' - ' to convert a "str" to "bytes" using the given text encoding, ' - 'and\n' - ' "bytes.decode()" can be used to achieve the opposite.\n' - '\n' - 'Tuples\n' - ' The items of a tuple are arbitrary Python objects. Tuples of two ' - 'or\n' - ' more items are formed by comma-separated lists of expressions. ' - 'A\n' - ' tuple of one item (a ‘singleton’) can be formed by affixing a ' - 'comma\n' - ' to an expression (an expression by itself does not create a ' - 'tuple,\n' - ' since parentheses must be usable for grouping of expressions). ' - 'An\n' - ' empty tuple can be formed by an empty pair of parentheses.\n' - '\n' - 'Bytes\n' - ' A bytes object is an immutable array. The items are 8-bit ' - 'bytes,\n' - ' represented by integers in the range 0 <= x < 256. Bytes ' - 'literals\n' - ' (like "b\'abc\'") and the built-in "bytes()" constructor can be ' - 'used\n' - ' to create bytes objects. Also, bytes objects can be decoded to\n' - ' strings via the "decode()" method.\n' - '\n' - '\n' - 'Mutable sequences\n' - '-----------------\n' - '\n' - 'Mutable sequences can be changed after they are created. The\n' - 'subscription and slicing notations can be used as the target of\n' - 'assignment and "del" (delete) statements.\n' - '\n' - 'Note:\n' - '\n' - ' The "collections" and "array" module provide additional examples ' - 'of\n' - ' mutable sequence types.\n' - '\n' - 'There are currently two intrinsic mutable sequence types:\n' - '\n' - 'Lists\n' - ' The items of a list are arbitrary Python objects. Lists are ' - 'formed\n' - ' by placing a comma-separated list of expressions in square\n' - ' brackets. (Note that there are no special cases needed to form\n' - ' lists of length 0 or 1.)\n' - '\n' - 'Byte Arrays\n' - ' A bytearray object is a mutable array. They are created by the\n' - ' built-in "bytearray()" constructor. Aside from being mutable ' - '(and\n' - ' hence unhashable), byte arrays otherwise provide the same ' - 'interface\n' - ' and functionality as immutable "bytes" objects.\n' - '\n' - '\n' - 'Set types\n' - '=========\n' - '\n' - 'These represent unordered, finite sets of unique, immutable ' - 'objects.\n' - 'As such, they cannot be indexed by any subscript. However, they can ' - 'be\n' - 'iterated over, and the built-in function "len()" returns the number ' - 'of\n' - 'items in a set. Common uses for sets are fast membership testing,\n' - 'removing duplicates from a sequence, and computing mathematical\n' - 'operations such as intersection, union, difference, and symmetric\n' - 'difference.\n' - '\n' - 'For set elements, the same immutability rules apply as for ' - 'dictionary\n' - 'keys. Note that numeric types obey the normal rules for numeric\n' - 'comparison: if two numbers compare equal (e.g., "1" and "1.0"), ' - 'only\n' - 'one of them can be contained in a set.\n' - '\n' - 'There are currently two intrinsic set types:\n' - '\n' - 'Sets\n' - ' These represent a mutable set. They are created by the built-in\n' - ' "set()" constructor and can be modified afterwards by several\n' - ' methods, such as "add()".\n' - '\n' - 'Frozen sets\n' - ' These represent an immutable set. They are created by the ' - 'built-in\n' - ' "frozenset()" constructor. As a frozenset is immutable and\n' - ' *hashable*, it can be used again as an element of another set, ' - 'or\n' - ' as a dictionary key.\n' - '\n' - '\n' - 'Mappings\n' - '========\n' - '\n' - 'These represent finite sets of objects indexed by arbitrary index\n' - 'sets. The subscript notation "a[k]" selects the item indexed by ' - '"k"\n' - 'from the mapping "a"; this can be used in expressions and as the\n' - 'target of assignments or "del" statements. The built-in function\n' - '"len()" returns the number of items in a mapping.\n' - '\n' - 'There is currently a single intrinsic mapping type:\n' - '\n' - '\n' - 'Dictionaries\n' - '------------\n' - '\n' - 'These represent finite sets of objects indexed by nearly arbitrary\n' - 'values. The only types of values not acceptable as keys are ' - 'values\n' - 'containing lists or dictionaries or other mutable types that are\n' - 'compared by value rather than by object identity, the reason being\n' - 'that the efficient implementation of dictionaries requires a key’s\n' - 'hash value to remain constant. Numeric types used for keys obey ' - 'the\n' - 'normal rules for numeric comparison: if two numbers compare equal\n' - '(e.g., "1" and "1.0") then they can be used interchangeably to ' - 'index\n' - 'the same dictionary entry.\n' - '\n' - 'Dictionaries preserve insertion order, meaning that keys will be\n' - 'produced in the same order they were added sequentially over the\n' - 'dictionary. Replacing an existing key does not change the order,\n' - 'however removing a key and re-inserting it will add it to the end\n' - 'instead of keeping its old place.\n' - '\n' - 'Dictionaries are mutable; they can be created by the "{}" notation\n' - '(see section Dictionary displays).\n' - '\n' - 'The extension modules "dbm.ndbm" and "dbm.gnu" provide additional\n' - 'examples of mapping types, as does the "collections" module.\n' - '\n' - 'Changed in version 3.7: Dictionaries did not preserve insertion ' - 'order\n' - 'in versions of Python before 3.6. In CPython 3.6, insertion order ' - 'was\n' - 'preserved, but it was considered an implementation detail at that ' - 'time\n' - 'rather than a language guarantee.\n' - '\n' - '\n' - 'Callable types\n' - '==============\n' - '\n' - 'These are the types to which the function call operation (see ' - 'section\n' - 'Calls) can be applied:\n' - '\n' - '\n' - 'User-defined functions\n' - '----------------------\n' - '\n' - 'A user-defined function object is created by a function definition\n' - '(see section Function definitions). It should be called with an\n' - 'argument list containing the same number of items as the ' - 'function’s\n' - 'formal parameter list.\n' - '\n' - '\n' - 'Special read-only attributes\n' - '~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| Attribute | ' - 'Meaning |\n' - '|====================================================|====================================================|\n' - '| function.__globals__ | A reference ' - 'to the "dictionary" that holds the |\n' - '| | function’s ' - 'global variables – the global namespace |\n' - '| | of the ' - 'module in which the function was defined. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__closure__ | "None" or a ' - '"tuple" of cells that contain bindings |\n' - '| | for the ' - 'names specified in the "co_freevars" |\n' - '| | attribute of ' - 'the function’s "code object". A cell |\n' - '| | object has ' - 'the attribute "cell_contents". This can |\n' - '| | be used to ' - 'get the value of the cell, as well as |\n' - '| | set the ' - 'value. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - '\n' - 'Special writable attributes\n' - '~~~~~~~~~~~~~~~~~~~~~~~~~~~\n' - '\n' - 'Most of these attributes check the type of the assigned value:\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| Attribute | ' - 'Meaning |\n' - '|====================================================|====================================================|\n' - '| function.__doc__ | The ' - 'function’s documentation string, or "None" if |\n' - '| | ' - 'unavailable. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__name__ | The ' - 'function’s name. See also: "__name__ |\n' - '| | ' - 'attributes". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__qualname__ | The ' - 'function’s *qualified name*. See also: |\n' - '| | ' - '"__qualname__ attributes". Added in version 3.3. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__module__ | The name of ' - 'the module the function was defined |\n' - '| | in, or ' - '"None" if unavailable. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__defaults__ | A "tuple" ' - 'containing default *parameter* values |\n' - '| | for those ' - 'parameters that have defaults, or "None" |\n' - '| | if no ' - 'parameters have a default value. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__code__ | The code ' - 'object representing the compiled function |\n' - '| | ' - 'body. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__dict__ | The ' - 'namespace supporting arbitrary function |\n' - '| | attributes. ' - 'See also: "__dict__ attributes". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__annotations__ | A ' - '"dictionary" containing annotations of |\n' - '| | ' - '*parameters*. The keys of the dictionary are the |\n' - '| | parameter ' - 'names, and "\'return\'" for the return |\n' - '| | annotation, ' - 'if provided. See also: |\n' - '| | ' - '"object.__annotations__". Changed in version |\n' - '| | 3.14: ' - 'Annotations are now lazily evaluated. See |\n' - '| | **PEP ' - '649**. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__annotate__ | The ' - '*annotate function* for this function, or |\n' - '| | "None" if ' - 'the function has no annotations. See |\n' - '| | ' - '"object.__annotate__". Added in version 3.14. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__kwdefaults__ | A ' - '"dictionary" containing defaults for keyword- |\n' - '| | only ' - '*parameters*. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| function.__type_params__ | A "tuple" ' - 'containing the type parameters of a |\n' - '| | generic ' - 'function. Added in version 3.12. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - 'Function objects also support getting and setting arbitrary\n' - 'attributes, which can be used, for example, to attach metadata to\n' - 'functions. Regular attribute dot-notation is used to get and set ' - 'such\n' - 'attributes.\n' - '\n' - '**CPython implementation detail:** CPython’s current ' - 'implementation\n' - 'only supports function attributes on user-defined functions. ' - 'Function\n' - 'attributes on built-in functions may be supported in the future.\n' - '\n' - 'Additional information about a function’s definition can be ' - 'retrieved\n' - 'from its code object (accessible via the "__code__" attribute).\n' - '\n' - '\n' - 'Instance methods\n' - '----------------\n' - '\n' - 'An instance method object combines a class, a class instance and ' - 'any\n' - 'callable object (normally a user-defined function).\n' - '\n' - 'Special read-only attributes:\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| method.__self__ | Refers to ' - 'the class instance object to which the |\n' - '| | method is ' - 'bound |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| method.__func__ | Refers to ' - 'the original function object |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| method.__doc__ | The method’s ' - 'documentation (same as |\n' - '| | ' - '"method.__func__.__doc__"). A "string" if the |\n' - '| | original ' - 'function had a docstring, else "None". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| method.__name__ | The name of ' - 'the method (same as |\n' - '| | ' - '"method.__func__.__name__") |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| method.__module__ | The name of ' - 'the module the method was defined in, |\n' - '| | or "None" if ' - 'unavailable. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - 'Methods also support accessing (but not setting) the arbitrary\n' - 'function attributes on the underlying function object.\n' - '\n' - 'User-defined method objects may be created when getting an ' - 'attribute\n' - 'of a class (perhaps via an instance of that class), if that ' - 'attribute\n' - 'is a user-defined function object or a "classmethod" object.\n' - '\n' - 'When an instance method object is created by retrieving a ' - 'user-defined\n' - 'function object from a class via one of its instances, its ' - '"__self__"\n' - 'attribute is the instance, and the method object is said to be\n' - '*bound*. The new method’s "__func__" attribute is the original\n' - 'function object.\n' - '\n' - 'When an instance method object is created by retrieving a\n' - '"classmethod" object from a class or instance, its "__self__"\n' - 'attribute is the class itself, and its "__func__" attribute is the\n' - 'function object underlying the class method.\n' - '\n' - 'When an instance method object is called, the underlying function\n' - '("__func__") is called, inserting the class instance ("__self__") ' - 'in\n' - 'front of the argument list. For instance, when "C" is a class ' - 'which\n' - 'contains a definition for a function "f()", and "x" is an instance ' - 'of\n' - '"C", calling "x.f(1)" is equivalent to calling "C.f(x, 1)".\n' - '\n' - 'When an instance method object is derived from a "classmethod" ' - 'object,\n' - 'the “class instance” stored in "__self__" will actually be the ' - 'class\n' - 'itself, so that calling either "x.f(1)" or "C.f(1)" is equivalent ' - 'to\n' - 'calling "f(C,1)" where "f" is the underlying function.\n' - '\n' - 'It is important to note that user-defined functions which are\n' - 'attributes of a class instance are not converted to bound methods;\n' - 'this *only* happens when the function is an attribute of the ' - 'class.\n' - '\n' - '\n' - 'Generator functions\n' - '-------------------\n' - '\n' - 'A function or method which uses the "yield" statement (see section ' - 'The\n' - 'yield statement) is called a *generator function*. Such a ' - 'function,\n' - 'when called, always returns an *iterator* object which can be used ' - 'to\n' - 'execute the body of the function: calling the iterator’s\n' - '"iterator.__next__()" method will cause the function to execute ' - 'until\n' - 'it provides a value using the "yield" statement. When the ' - 'function\n' - 'executes a "return" statement or falls off the end, a ' - '"StopIteration"\n' - 'exception is raised and the iterator will have reached the end of ' - 'the\n' - 'set of values to be returned.\n' - '\n' - '\n' - 'Coroutine functions\n' - '-------------------\n' - '\n' - 'A function or method which is defined using "async def" is called ' - 'a\n' - '*coroutine function*. Such a function, when called, returns a\n' - '*coroutine* object. It may contain "await" expressions, as well ' - 'as\n' - '"async with" and "async for" statements. See also the Coroutine\n' - 'Objects section.\n' - '\n' - '\n' - 'Asynchronous generator functions\n' - '--------------------------------\n' - '\n' - 'A function or method which is defined using "async def" and which ' - 'uses\n' - 'the "yield" statement is called a *asynchronous generator ' - 'function*.\n' - 'Such a function, when called, returns an *asynchronous iterator*\n' - 'object which can be used in an "async for" statement to execute ' - 'the\n' - 'body of the function.\n' - '\n' - 'Calling the asynchronous iterator’s "aiterator.__anext__" method ' - 'will\n' - 'return an *awaitable* which when awaited will execute until it\n' - 'provides a value using the "yield" expression. When the function\n' - 'executes an empty "return" statement or falls off the end, a\n' - '"StopAsyncIteration" exception is raised and the asynchronous ' - 'iterator\n' - 'will have reached the end of the set of values to be yielded.\n' - '\n' - '\n' - 'Built-in functions\n' - '------------------\n' - '\n' - 'A built-in function object is a wrapper around a C function. ' - 'Examples\n' - 'of built-in functions are "len()" and "math.sin()" ("math" is a\n' - 'standard built-in module). The number and type of the arguments ' - 'are\n' - 'determined by the C function. Special read-only attributes:\n' - '\n' - '* "__doc__" is the function’s documentation string, or "None" if\n' - ' unavailable. See "function.__doc__".\n' - '\n' - '* "__name__" is the function’s name. See "function.__name__".\n' - '\n' - '* "__self__" is set to "None" (but see the next item).\n' - '\n' - '* "__module__" is the name of the module the function was defined ' - 'in\n' - ' or "None" if unavailable. See "function.__module__".\n' - '\n' - '\n' - 'Built-in methods\n' - '----------------\n' - '\n' - 'This is really a different disguise of a built-in function, this ' - 'time\n' - 'containing an object passed to the C function as an implicit extra\n' - 'argument. An example of a built-in method is "alist.append()",\n' - 'assuming *alist* is a list object. In this case, the special ' - 'read-only\n' - 'attribute "__self__" is set to the object denoted by *alist*. (The\n' - 'attribute has the same semantics as it does with "other instance\n' - 'methods".)\n' - '\n' - '\n' - 'Classes\n' - '-------\n' - '\n' - 'Classes are callable. These objects normally act as factories for ' - 'new\n' - 'instances of themselves, but variations are possible for class ' - 'types\n' - 'that override "__new__()". The arguments of the call are passed ' - 'to\n' - '"__new__()" and, in the typical case, to "__init__()" to ' - 'initialize\n' - 'the new instance.\n' - '\n' - '\n' - 'Class Instances\n' - '---------------\n' - '\n' - 'Instances of arbitrary classes can be made callable by defining a\n' - '"__call__()" method in their class.\n' - '\n' - '\n' - 'Modules\n' - '=======\n' - '\n' - 'Modules are a basic organizational unit of Python code, and are\n' - 'created by the import system as invoked either by the "import"\n' - 'statement, or by calling functions such as ' - '"importlib.import_module()"\n' - 'and built-in "__import__()". A module object has a namespace\n' - 'implemented by a "dictionary" object (this is the dictionary\n' - 'referenced by the "__globals__" attribute of functions defined in ' - 'the\n' - 'module). Attribute references are translated to lookups in this\n' - 'dictionary, e.g., "m.x" is equivalent to "m.__dict__["x"]". A ' - 'module\n' - 'object does not contain the code object used to initialize the ' - 'module\n' - '(since it isn’t needed once the initialization is done).\n' - '\n' - 'Attribute assignment updates the module’s namespace dictionary, ' - 'e.g.,\n' - '"m.x = 1" is equivalent to "m.__dict__["x"] = 1".\n' - '\n' - '\n' - 'Import-related attributes on module objects\n' - '-------------------------------------------\n' - '\n' - 'Module objects have the following attributes that relate to the ' - 'import\n' - 'system. When a module is created using the machinery associated ' - 'with\n' - 'the import system, these attributes are filled in based on the\n' - 'module’s *spec*, before the *loader* executes and loads the ' - 'module.\n' - '\n' - 'To create a module dynamically rather than using the import ' - 'system,\n' - 'it’s recommended to use "importlib.util.module_from_spec()", which\n' - 'will set the various import-controlled attributes to appropriate\n' - 'values. It’s also possible to use the "types.ModuleType" ' - 'constructor\n' - 'to create modules directly, but this technique is more error-prone, ' - 'as\n' - 'most attributes must be manually set on the module object after it ' - 'has\n' - 'been created when using this approach.\n' - '\n' - 'Caution:\n' - '\n' - ' With the exception of "__name__", it is **strongly** recommended\n' - ' that you rely on "__spec__" and its attributes instead of any of ' - 'the\n' - ' other individual attributes listed in this subsection. Note that\n' - ' updating an attribute on "__spec__" will not update the\n' - ' corresponding attribute on the module itself:\n' - '\n' - ' >>> import typing\n' - ' >>> typing.__name__, typing.__spec__.name\n' - " ('typing', 'typing')\n" - " >>> typing.__spec__.name = 'spelling'\n" - ' >>> typing.__name__, typing.__spec__.name\n' - " ('typing', 'spelling')\n" - " >>> typing.__name__ = 'keyboard_smashing'\n" - ' >>> typing.__name__, typing.__spec__.name\n' - " ('keyboard_smashing', 'spelling')\n" - '\n' - 'module.__name__\n' - '\n' - ' The name used to uniquely identify the module in the import ' - 'system.\n' - ' For a directly executed module, this will be set to ' - '""__main__"".\n' - '\n' - ' This attribute must be set to the fully qualified name of the\n' - ' module. It is expected to match the value of\n' - ' "module.__spec__.name".\n' - '\n' - 'module.__spec__\n' - '\n' - ' A record of the module’s import-system-related state.\n' - '\n' - ' Set to the "module spec" that was used when importing the ' - 'module.\n' - ' See Module specs for more details.\n' - '\n' - ' Added in version 3.4.\n' - '\n' - 'module.__package__\n' - '\n' - ' The *package* a module belongs to.\n' - '\n' - ' If the module is top-level (that is, not a part of any specific\n' - ' package) then the attribute should be set to "\'\'" (the empty\n' - ' string). Otherwise, it should be set to the name of the ' - 'module’s\n' - ' package (which can be equal to "module.__name__" if the module\n' - ' itself is a package). See **PEP 366** for further details.\n' - '\n' - ' This attribute is used instead of "__name__" to calculate ' - 'explicit\n' - ' relative imports for main modules. It defaults to "None" for\n' - ' modules created dynamically using the "types.ModuleType"\n' - ' constructor; use "importlib.util.module_from_spec()" instead to\n' - ' ensure the attribute is set to a "str".\n' - '\n' - ' It is **strongly** recommended that you use\n' - ' "module.__spec__.parent" instead of "module.__package__".\n' - ' "__package__" is now only used as a fallback if ' - '"__spec__.parent"\n' - ' is not set, and this fallback path is deprecated.\n' - '\n' - ' Changed in version 3.4: This attribute now defaults to "None" ' - 'for\n' - ' modules created dynamically using the "types.ModuleType"\n' - ' constructor. Previously the attribute was optional.\n' - '\n' - ' Changed in version 3.6: The value of "__package__" is expected ' - 'to\n' - ' be the same as "__spec__.parent". "__package__" is now only used ' - 'as\n' - ' a fallback during import resolution if "__spec__.parent" is not\n' - ' defined.\n' - '\n' - ' Changed in version 3.10: "ImportWarning" is raised if an import\n' - ' resolution falls back to "__package__" instead of\n' - ' "__spec__.parent".\n' - '\n' - ' Changed in version 3.12: Raise "DeprecationWarning" instead of\n' - ' "ImportWarning" when falling back to "__package__" during ' - 'import\n' - ' resolution.\n' - '\n' - ' Deprecated since version 3.13, will be removed in version 3.15:\n' - ' "__package__" will cease to be set or taken into consideration ' - 'by\n' - ' the import system or standard library.\n' - '\n' - 'module.__loader__\n' - '\n' - ' The *loader* object that the import machinery used to load the\n' - ' module.\n' - '\n' - ' This attribute is mostly useful for introspection, but can be ' - 'used\n' - ' for additional loader-specific functionality, for example ' - 'getting\n' - ' data associated with a loader.\n' - '\n' - ' "__loader__" defaults to "None" for modules created dynamically\n' - ' using the "types.ModuleType" constructor; use\n' - ' "importlib.util.module_from_spec()" instead to ensure the ' - 'attribute\n' - ' is set to a *loader* object.\n' - '\n' - ' It is **strongly** recommended that you use\n' - ' "module.__spec__.loader" instead of "module.__loader__".\n' - '\n' - ' Changed in version 3.4: This attribute now defaults to "None" ' - 'for\n' - ' modules created dynamically using the "types.ModuleType"\n' - ' constructor. Previously the attribute was optional.\n' - '\n' - ' Deprecated since version 3.12, will be removed in version 3.16:\n' - ' Setting "__loader__" on a module while failing to set\n' - ' "__spec__.loader" is deprecated. In Python 3.16, "__loader__" ' - 'will\n' - ' cease to be set or taken into consideration by the import system ' - 'or\n' - ' the standard library.\n' - '\n' - 'module.__path__\n' - '\n' - ' A (possibly empty) *sequence* of strings enumerating the ' - 'locations\n' - ' where the package’s submodules will be found. Non-package ' - 'modules\n' - ' should not have a "__path__" attribute. See __path__ attributes ' - 'on\n' - ' modules for more details.\n' - '\n' - ' It is **strongly** recommended that you use\n' - ' "module.__spec__.submodule_search_locations" instead of\n' - ' "module.__path__".\n' - '\n' - 'module.__file__\n' - '\n' - 'module.__cached__\n' - '\n' - ' "__file__" and "__cached__" are both optional attributes that ' - 'may\n' - ' or may not be set. Both attributes should be a "str" when they ' - 'are\n' - ' available.\n' - '\n' - ' "__file__" indicates the pathname of the file from which the ' - 'module\n' - ' was loaded (if loaded from a file), or the pathname of the ' - 'shared\n' - ' library file for extension modules loaded dynamically from a ' - 'shared\n' - ' library. It might be missing for certain types of modules, such ' - 'as\n' - ' C modules that are statically linked into the interpreter, and ' - 'the\n' - ' import system may opt to leave it unset if it has no semantic\n' - ' meaning (for example, a module loaded from a database).\n' - '\n' - ' If "__file__" is set then the "__cached__" attribute might also ' - 'be\n' - ' set, which is the path to any compiled version of the code ' - '(for\n' - ' example, a byte-compiled file). The file does not need to exist ' - 'to\n' - ' set this attribute; the path can simply point to where the ' - 'compiled\n' - ' file *would* exist (see **PEP 3147**).\n' - '\n' - ' Note that "__cached__" may be set even if "__file__" is not ' - 'set.\n' - ' However, that scenario is quite atypical. Ultimately, the ' - '*loader*\n' - ' is what makes use of the module spec provided by the *finder* ' - '(from\n' - ' which "__file__" and "__cached__" are derived). So if a loader ' - 'can\n' - ' load from a cached module but otherwise does not load from a ' - 'file,\n' - ' that atypical scenario may be appropriate.\n' - '\n' - ' It is **strongly** recommended that you use\n' - ' "module.__spec__.cached" instead of "module.__cached__".\n' - '\n' - ' Deprecated since version 3.13, will be removed in version 3.15:\n' - ' Setting "__cached__" on a module while failing to set\n' - ' "__spec__.cached" is deprecated. In Python 3.15, "__cached__" ' - 'will\n' - ' cease to be set or taken into consideration by the import system ' - 'or\n' - ' standard library.\n' - '\n' - '\n' - 'Other writable attributes on module objects\n' - '-------------------------------------------\n' - '\n' - 'As well as the import-related attributes listed above, module ' - 'objects\n' - 'also have the following writable attributes:\n' - '\n' - 'module.__doc__\n' - '\n' - ' The module’s documentation string, or "None" if unavailable. ' - 'See\n' - ' also: "__doc__ attributes".\n' - '\n' - 'module.__annotations__\n' - '\n' - ' A dictionary containing *variable annotations* collected during\n' - ' module body execution. For best practices on working with\n' - ' "__annotations__", see "annotationlib".\n' - '\n' - ' Changed in version 3.14: Annotations are now lazily evaluated. ' - 'See\n' - ' **PEP 649**.\n' - '\n' - 'module.__annotate__\n' - '\n' - ' The *annotate function* for this module, or "None" if the ' - 'module\n' - ' has no annotations. See also: "__annotate__" attributes.\n' - '\n' - ' Added in version 3.14.\n' - '\n' - '\n' - 'Module dictionaries\n' - '-------------------\n' - '\n' - 'Module objects also have the following special read-only ' - 'attribute:\n' - '\n' - 'module.__dict__\n' - '\n' - ' The module’s namespace as a dictionary object. Uniquely among ' - 'the\n' - ' attributes listed here, "__dict__" cannot be accessed as a ' - 'global\n' - ' variable from within a module; it can only be accessed as an\n' - ' attribute on module objects.\n' - '\n' - ' **CPython implementation detail:** Because of the way CPython\n' - ' clears module dictionaries, the module dictionary will be ' - 'cleared\n' - ' when the module falls out of scope even if the dictionary still ' - 'has\n' - ' live references. To avoid this, copy the dictionary or keep ' - 'the\n' - ' module around while using its dictionary directly.\n' - '\n' - '\n' - 'Custom classes\n' - '==============\n' - '\n' - 'Custom class types are typically created by class definitions (see\n' - 'section Class definitions). A class has a namespace implemented by ' - 'a\n' - 'dictionary object. Class attribute references are translated to\n' - 'lookups in this dictionary, e.g., "C.x" is translated to\n' - '"C.__dict__["x"]" (although there are a number of hooks which ' - 'allow\n' - 'for other means of locating attributes). When the attribute name ' - 'is\n' - 'not found there, the attribute search continues in the base ' - 'classes.\n' - 'This search of the base classes uses the C3 method resolution ' - 'order\n' - 'which behaves correctly even in the presence of ‘diamond’ ' - 'inheritance\n' - 'structures where there are multiple inheritance paths leading back ' - 'to\n' - 'a common ancestor. Additional details on the C3 MRO used by Python ' - 'can\n' - 'be found at The Python 2.3 Method Resolution Order.\n' - '\n' - 'When a class attribute reference (for class "C", say) would yield ' - 'a\n' - 'class method object, it is transformed into an instance method ' - 'object\n' - 'whose "__self__" attribute is "C". When it would yield a\n' - '"staticmethod" object, it is transformed into the object wrapped ' - 'by\n' - 'the static method object. See section Implementing Descriptors for\n' - 'another way in which attributes retrieved from a class may differ ' - 'from\n' - 'those actually contained in its "__dict__".\n' - '\n' - 'Class attribute assignments update the class’s dictionary, never ' - 'the\n' - 'dictionary of a base class.\n' - '\n' - 'A class object can be called (see above) to yield a class instance\n' - '(see below).\n' - '\n' - '\n' - 'Special attributes\n' - '------------------\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| Attribute | ' - 'Meaning |\n' - '|====================================================|====================================================|\n' - '| type.__name__ | The class’s ' - 'name. See also: "__name__ attributes". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__qualname__ | The class’s ' - '*qualified name*. See also: |\n' - '| | ' - '"__qualname__ attributes". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__module__ | The name of ' - 'the module in which the class was |\n' - '| | ' - 'defined. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__dict__ | A "mapping ' - 'proxy" providing a read-only view of |\n' - '| | the class’s ' - 'namespace. See also: "__dict__ |\n' - '| | ' - 'attributes". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__bases__ | A "tuple" ' - 'containing the class’s bases. In most |\n' - '| | cases, for a ' - 'class defined as "class X(A, B, C)", |\n' - '| | ' - '"X.__bases__" will be exactly equal to "(A, B, |\n' - '| | ' - 'C)". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__doc__ | The class’s ' - 'documentation string, or "None" if |\n' - '| | undefined. ' - 'Not inherited by subclasses. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__annotations__ | A dictionary ' - 'containing *variable annotations* |\n' - '| | collected ' - 'during class body execution. See also: |\n' - '| | ' - '"__annotations__ attributes". For best practices |\n' - '| | on working ' - 'with "__annotations__", please see |\n' - '| | ' - '"annotationlib". Caution: Accessing the |\n' - '| | ' - '"__annotations__" attribute of a class object |\n' - '| | directly may ' - 'yield incorrect results in the |\n' - '| | presence of ' - 'metaclasses. In addition, the |\n' - '| | attribute ' - 'may not exist for some classes. Use |\n' - '| | ' - '"annotationlib.get_annotations()" to retrieve |\n' - '| | class ' - 'annotations safely. Changed in version |\n' - '| | 3.14: ' - 'Annotations are now lazily evaluated. See |\n' - '| | **PEP ' - '649**. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__annotate__() | The ' - '*annotate function* for this class, or "None" |\n' - '| | if the class ' - 'has no annotations. See also: |\n' - '| | ' - '"__annotate__ attributes". Caution: Accessing |\n' - '| | the ' - '"__annotate__" attribute of a class object |\n' - '| | directly may ' - 'yield incorrect results in the |\n' - '| | presence of ' - 'metaclasses. Use |\n' - '| | ' - '"annotationlib.get_annotate_function()" to |\n' - '| | retrieve the ' - 'annotate function safely. Added in |\n' - '| | version ' - '3.14. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__type_params__ | A "tuple" ' - 'containing the type parameters of a |\n' - '| | generic ' - 'class. Added in version 3.12. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__static_attributes__ | A "tuple" ' - 'containing names of attributes of this |\n' - '| | class which ' - 'are assigned through "self.X" from any |\n' - '| | function in ' - 'its body. Added in version 3.13. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__firstlineno__ | The line ' - 'number of the first line of the class |\n' - '| | definition, ' - 'including decorators. Setting the |\n' - '| | "__module__" ' - 'attribute removes the |\n' - '| | ' - '"__firstlineno__" item from the type’s dictionary. |\n' - '| | Added in ' - 'version 3.13. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| type.__mro__ | The "tuple" ' - 'of classes that are considered when |\n' - '| | looking for ' - 'base classes during method resolution. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - '\n' - 'Special methods\n' - '---------------\n' - '\n' - 'In addition to the special attributes described above, all Python\n' - 'classes also have the following two methods available:\n' - '\n' - 'type.mro()\n' - '\n' - ' This method can be overridden by a metaclass to customize the\n' - ' method resolution order for its instances. It is called at ' - 'class\n' - ' instantiation, and its result is stored in "__mro__".\n' - '\n' - 'type.__subclasses__()\n' - '\n' - ' Each class keeps a list of weak references to its immediate\n' - ' subclasses. This method returns a list of all those references\n' - ' still alive. The list is in definition order. Example:\n' - '\n' - ' >>> class A: pass\n' - ' >>> class B(A): pass\n' - ' >>> A.__subclasses__()\n' - " [<class 'B'>]\n" - '\n' - '\n' - 'Class instances\n' - '===============\n' - '\n' - 'A class instance is created by calling a class object (see above). ' - 'A\n' - 'class instance has a namespace implemented as a dictionary which ' - 'is\n' - 'the first place in which attribute references are searched. When ' - 'an\n' - 'attribute is not found there, and the instance’s class has an\n' - 'attribute by that name, the search continues with the class\n' - 'attributes. If a class attribute is found that is a user-defined\n' - 'function object, it is transformed into an instance method object\n' - 'whose "__self__" attribute is the instance. Static method and ' - 'class\n' - 'method objects are also transformed; see above under “Classes”. ' - 'See\n' - 'section Implementing Descriptors for another way in which ' - 'attributes\n' - 'of a class retrieved via its instances may differ from the objects\n' - 'actually stored in the class’s "__dict__". If no class attribute ' - 'is\n' - 'found, and the object’s class has a "__getattr__()" method, that ' - 'is\n' - 'called to satisfy the lookup.\n' - '\n' - 'Attribute assignments and deletions update the instance’s ' - 'dictionary,\n' - 'never a class’s dictionary. If the class has a "__setattr__()" or\n' - '"__delattr__()" method, this is called instead of updating the\n' - 'instance dictionary directly.\n' - '\n' - 'Class instances can pretend to be numbers, sequences, or mappings ' - 'if\n' - 'they have methods with certain special names. See section Special\n' - 'method names.\n' - '\n' - '\n' - 'Special attributes\n' - '------------------\n' - '\n' - 'object.__class__\n' - '\n' - ' The class to which a class instance belongs.\n' - '\n' - 'object.__dict__\n' - '\n' - ' A dictionary or other mapping object used to store an object’s\n' - ' (writable) attributes. Not all instances have a "__dict__"\n' - ' attribute; see the section on __slots__ for more details.\n' - '\n' - '\n' - 'I/O objects (also known as file objects)\n' - '========================================\n' - '\n' - 'A *file object* represents an open file. Various shortcuts are\n' - 'available to create file objects: the "open()" built-in function, ' - 'and\n' - 'also "os.popen()", "os.fdopen()", and the "makefile()" method of\n' - 'socket objects (and perhaps by other functions or methods provided ' - 'by\n' - 'extension modules).\n' - '\n' - 'The objects "sys.stdin", "sys.stdout" and "sys.stderr" are ' - 'initialized\n' - 'to file objects corresponding to the interpreter’s standard input,\n' - 'output and error streams; they are all open in text mode and ' - 'therefore\n' - 'follow the interface defined by the "io.TextIOBase" abstract ' - 'class.\n' - '\n' - '\n' - 'Internal types\n' - '==============\n' - '\n' - 'A few types used internally by the interpreter are exposed to the\n' - 'user. Their definitions may change with future versions of the\n' - 'interpreter, but they are mentioned here for completeness.\n' - '\n' - '\n' - 'Code objects\n' - '------------\n' - '\n' - 'Code objects represent *byte-compiled* executable Python code, or\n' - '*bytecode*. The difference between a code object and a function ' - 'object\n' - 'is that the function object contains an explicit reference to the\n' - 'function’s globals (the module in which it was defined), while a ' - 'code\n' - 'object contains no context; also the default argument values are\n' - 'stored in the function object, not in the code object (because ' - 'they\n' - 'represent values calculated at run-time). Unlike function ' - 'objects,\n' - 'code objects are immutable and contain no references (directly or\n' - 'indirectly) to mutable objects.\n' - '\n' - '\n' - 'Special read-only attributes\n' - '~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_name | The function ' - 'name |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_qualname | The fully ' - 'qualified function name Added in |\n' - '| | version ' - '3.11. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_argcount | The total ' - 'number of positional *parameters* |\n' - '| | (including ' - 'positional-only parameters and |\n' - '| | parameters ' - 'with default values) that the function |\n' - '| | ' - 'has |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_posonlyargcount | The number ' - 'of positional-only *parameters* |\n' - '| | (including ' - 'arguments with default values) that the |\n' - '| | function ' - 'has |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_kwonlyargcount | The number ' - 'of keyword-only *parameters* (including |\n' - '| | arguments ' - 'with default values) that the function |\n' - '| | ' - 'has |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_nlocals | The number ' - 'of local variables used by the function |\n' - '| | (including ' - 'parameters) |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_varnames | A "tuple" ' - 'containing the names of the local |\n' - '| | variables in ' - 'the function (starting with the |\n' - '| | parameter ' - 'names) |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_cellvars | A "tuple" ' - 'containing the names of local variables |\n' - '| | that are ' - 'referenced from at least one *nested |\n' - '| | scope* ' - 'inside the function |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_freevars | A "tuple" ' - 'containing the names of *free (closure) |\n' - '| | variables* ' - 'that a *nested scope* references in an |\n' - '| | outer scope. ' - 'See also "function.__closure__". |\n' - '| | Note: ' - 'references to global and builtin names are |\n' - '| | *not* ' - 'included. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_code | A string ' - 'representing the sequence of *bytecode* |\n' - '| | instructions ' - 'in the function |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_consts | A "tuple" ' - 'containing the literals used by the |\n' - '| | *bytecode* ' - 'in the function |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_names | A "tuple" ' - 'containing the names used by the |\n' - '| | *bytecode* ' - 'in the function |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_filename | The name of ' - 'the file from which the code was |\n' - '| | ' - 'compiled |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_firstlineno | The line ' - 'number of the first line of the function |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_lnotab | A string ' - 'encoding the mapping from *bytecode* |\n' - '| | offsets to ' - 'line numbers. For details, see the |\n' - '| | source code ' - 'of the interpreter. Deprecated since |\n' - '| | version ' - '3.12: This attribute of code objects is |\n' - '| | deprecated, ' - 'and may be removed in Python 3.15. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_stacksize | The required ' - 'stack size of the code object |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| codeobject.co_flags | An "integer" ' - 'encoding a number of flags for the |\n' - '| | ' - 'interpreter. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - 'The following flag bits are defined for "co_flags": bit "0x04" is ' - 'set\n' - 'if the function uses the "*arguments" syntax to accept an ' - 'arbitrary\n' - 'number of positional arguments; bit "0x08" is set if the function ' - 'uses\n' - 'the "**keywords" syntax to accept arbitrary keyword arguments; bit\n' - '"0x20" is set if the function is a generator. See Code Objects Bit\n' - 'Flags for details on the semantics of each flags that might be\n' - 'present.\n' - '\n' - 'Future feature declarations ("from __future__ import division") ' - 'also\n' - 'use bits in "co_flags" to indicate whether a code object was ' - 'compiled\n' - 'with a particular feature enabled: bit "0x2000" is set if the ' - 'function\n' - 'was compiled with future division enabled; bits "0x10" and ' - '"0x1000"\n' - 'were used in earlier versions of Python.\n' - '\n' - 'Other bits in "co_flags" are reserved for internal use.\n' - '\n' - 'If a code object represents a function and has a docstring, the ' - 'first\n' - 'item in "co_consts" is the docstring of the function.\n' - '\n' - '\n' - 'Methods on code objects\n' - '~~~~~~~~~~~~~~~~~~~~~~~\n' - '\n' - 'codeobject.co_positions()\n' - '\n' - ' Returns an iterable over the source code positions of each\n' - ' *bytecode* instruction in the code object.\n' - '\n' - ' The iterator returns "tuple"s containing the "(start_line,\n' - ' end_line, start_column, end_column)". The *i-th* tuple ' - 'corresponds\n' - ' to the position of the source code that compiled to the *i-th* ' - 'code\n' - ' unit. Column information is 0-indexed utf-8 byte offsets on the\n' - ' given source line.\n' - '\n' - ' This positional information can be missing. A non-exhaustive ' - 'lists\n' - ' of cases where this may happen:\n' - '\n' - ' * Running the interpreter with "-X" "no_debug_ranges".\n' - '\n' - ' * Loading a pyc file compiled while using "-X" ' - '"no_debug_ranges".\n' - '\n' - ' * Position tuples corresponding to artificial instructions.\n' - '\n' - ' * Line and column numbers that can’t be represented due to\n' - ' implementation specific limitations.\n' - '\n' - ' When this occurs, some or all of the tuple elements can be ' - '"None".\n' - '\n' - ' Added in version 3.11.\n' - '\n' - ' Note:\n' - '\n' - ' This feature requires storing column positions in code ' - 'objects\n' - ' which may result in a small increase of disk usage of ' - 'compiled\n' - ' Python files or interpreter memory usage. To avoid storing ' - 'the\n' - ' extra information and/or deactivate printing the extra ' - 'traceback\n' - ' information, the "-X" "no_debug_ranges" command line flag or ' - 'the\n' - ' "PYTHONNODEBUGRANGES" environment variable can be used.\n' - '\n' - 'codeobject.co_lines()\n' - '\n' - ' Returns an iterator that yields information about successive ' - 'ranges\n' - ' of *bytecode*s. Each item yielded is a "(start, end, lineno)"\n' - ' "tuple":\n' - '\n' - ' * "start" (an "int") represents the offset (inclusive) of the ' - 'start\n' - ' of the *bytecode* range\n' - '\n' - ' * "end" (an "int") represents the offset (exclusive) of the end ' - 'of\n' - ' the *bytecode* range\n' - '\n' - ' * "lineno" is an "int" representing the line number of the\n' - ' *bytecode* range, or "None" if the bytecodes in the given ' - 'range\n' - ' have no line number\n' - '\n' - ' The items yielded will have the following properties:\n' - '\n' - ' * The first range yielded will have a "start" of 0.\n' - '\n' - ' * The "(start, end)" ranges will be non-decreasing and ' - 'consecutive.\n' - ' That is, for any pair of "tuple"s, the "start" of the second ' - 'will\n' - ' be equal to the "end" of the first.\n' - '\n' - ' * No range will be backwards: "end >= start" for all triples.\n' - '\n' - ' * The last "tuple" yielded will have "end" equal to the size of ' - 'the\n' - ' *bytecode*.\n' - '\n' - ' Zero-width ranges, where "start == end", are allowed. ' - 'Zero-width\n' - ' ranges are used for lines that are present in the source code, ' - 'but\n' - ' have been eliminated by the *bytecode* compiler.\n' - '\n' - ' Added in version 3.10.\n' - '\n' - ' See also:\n' - '\n' - ' **PEP 626** - Precise line numbers for debugging and other ' - 'tools.\n' - ' The PEP that introduced the "co_lines()" method.\n' - '\n' - 'codeobject.replace(**kwargs)\n' - '\n' - ' Return a copy of the code object with new values for the ' - 'specified\n' - ' fields.\n' - '\n' - ' Code objects are also supported by the generic function\n' - ' "copy.replace()".\n' - '\n' - ' Added in version 3.8.\n' - '\n' - '\n' - 'Frame objects\n' - '-------------\n' - '\n' - 'Frame objects represent execution frames. They may occur in ' - 'traceback\n' - 'objects, and are also passed to registered trace functions.\n' - '\n' - '\n' - 'Special read-only attributes\n' - '~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_back | Points to ' - 'the previous stack frame (towards the |\n' - '| | caller), or ' - '"None" if this is the bottom stack |\n' - '| | ' - 'frame |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_code | The code ' - 'object being executed in this frame. |\n' - '| | Accessing ' - 'this attribute raises an auditing event |\n' - '| | ' - '"object.__getattr__" with arguments "obj" and |\n' - '| | ' - '""f_code"". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_locals | The mapping ' - 'used by the frame to look up local |\n' - '| | variables. ' - 'If the frame refers to an *optimized |\n' - '| | scope*, this ' - 'may return a write-through proxy |\n' - '| | object. ' - 'Changed in version 3.13: Return a proxy |\n' - '| | for ' - 'optimized scopes. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_globals | The ' - 'dictionary used by the frame to look up global |\n' - '| | ' - 'variables |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_builtins | The ' - 'dictionary used by the frame to look up built- |\n' - '| | in ' - '(intrinsic) names |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_lasti | The “precise ' - 'instruction” of the frame object |\n' - '| | (this is an ' - 'index into the *bytecode* string of |\n' - '| | the code ' - 'object) |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - '\n' - 'Special writable attributes\n' - '~~~~~~~~~~~~~~~~~~~~~~~~~~~\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_trace | If not ' - '"None", this is a function called for |\n' - '| | various ' - 'events during code execution (this is used |\n' - '| | by ' - 'debuggers). Normally an event is triggered for |\n' - '| | each new ' - 'source line (see "f_trace_lines"). |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_trace_lines | Set this ' - 'attribute to "False" to disable |\n' - '| | triggering a ' - 'tracing event for each source line. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_trace_opcodes | Set this ' - 'attribute to "True" to allow per-opcode |\n' - '| | events to be ' - 'requested. Note that this may lead to |\n' - '| | undefined ' - 'interpreter behaviour if exceptions |\n' - '| | raised by ' - 'the trace function escape to the |\n' - '| | function ' - 'being traced. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| frame.f_lineno | The current ' - 'line number of the frame – writing to |\n' - '| | this from ' - 'within a trace function jumps to the |\n' - '| | given line ' - '(only for the bottom-most frame). A |\n' - '| | debugger can ' - 'implement a Jump command (aka Set |\n' - '| | Next ' - 'Statement) by writing to this attribute. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - '\n' - 'Frame object methods\n' - '~~~~~~~~~~~~~~~~~~~~\n' - '\n' - 'Frame objects support one method:\n' - '\n' - 'frame.clear()\n' - '\n' - ' This method clears all references to local variables held by ' - 'the\n' - ' frame. Also, if the frame belonged to a *generator*, the ' - 'generator\n' - ' is finalized. This helps break reference cycles involving ' - 'frame\n' - ' objects (for example when catching an exception and storing its\n' - ' traceback for later use).\n' - '\n' - ' "RuntimeError" is raised if the frame is currently executing or\n' - ' suspended.\n' - '\n' - ' Added in version 3.4.\n' - '\n' - ' Changed in version 3.13: Attempting to clear a suspended frame\n' - ' raises "RuntimeError" (as has always been the case for ' - 'executing\n' - ' frames).\n' - '\n' - '\n' - 'Traceback objects\n' - '-----------------\n' - '\n' - 'Traceback objects represent the stack trace of an exception. A\n' - 'traceback object is implicitly created when an exception occurs, ' - 'and\n' - 'may also be explicitly created by calling "types.TracebackType".\n' - '\n' - 'Changed in version 3.7: Traceback objects can now be explicitly\n' - 'instantiated from Python code.\n' - '\n' - 'For implicitly created tracebacks, when the search for an ' - 'exception\n' - 'handler unwinds the execution stack, at each unwound level a ' - 'traceback\n' - 'object is inserted in front of the current traceback. When an\n' - 'exception handler is entered, the stack trace is made available to ' - 'the\n' - 'program. (See section The try statement.) It is accessible as the\n' - 'third item of the tuple returned by "sys.exc_info()", and as the\n' - '"__traceback__" attribute of the caught exception.\n' - '\n' - 'When the program contains no suitable handler, the stack trace is\n' - 'written (nicely formatted) to the standard error stream; if the\n' - 'interpreter is interactive, it is also made available to the user ' - 'as\n' - '"sys.last_traceback".\n' - '\n' - 'For explicitly created tracebacks, it is up to the creator of the\n' - 'traceback to determine how the "tb_next" attributes should be ' - 'linked\n' - 'to form a full stack trace.\n' - '\n' - 'Special read-only attributes:\n' - '\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| traceback.tb_frame | Points to ' - 'the execution frame of the current |\n' - '| | level. ' - 'Accessing this attribute raises an |\n' - '| | auditing ' - 'event "object.__getattr__" with arguments |\n' - '| | "obj" and ' - '""tb_frame"". |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| traceback.tb_lineno | Gives the ' - 'line number where the exception occurred |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '| traceback.tb_lasti | Indicates ' - 'the “precise instruction”. |\n' - '+----------------------------------------------------+----------------------------------------------------+\n' - '\n' - 'The line number and last instruction in the traceback may differ ' - 'from\n' - 'the line number of its frame object if the exception occurred in a\n' - '"try" statement with no matching except clause or with a "finally"\n' - 'clause.\n' - '\n' - 'traceback.tb_next\n' - '\n' - ' The special writable attribute "tb_next" is the next level in ' - 'the\n' - ' stack trace (towards the frame where the exception occurred), ' - 'or\n' - ' "None" if there is no next level.\n' - '\n' - ' Changed in version 3.7: This attribute is now writable\n' - '\n' - '\n' - 'Slice objects\n' - '-------------\n' - '\n' - 'Slice objects are used to represent slices for "__getitem__()"\n' - 'methods. They are also created by the built-in "slice()" ' - 'function.\n' - '\n' - 'Special read-only attributes: "start" is the lower bound; "stop" ' - 'is\n' - 'the upper bound; "step" is the step value; each is "None" if ' - 'omitted.\n' - 'These attributes can have any type.\n' - '\n' - 'Slice objects support one method:\n' - '\n' - 'slice.indices(self, length)\n' - '\n' - ' This method takes a single integer argument *length* and ' - 'computes\n' - ' information about the slice that the slice object would describe ' - 'if\n' - ' applied to a sequence of *length* items. It returns a tuple of\n' - ' three integers; respectively these are the *start* and *stop*\n' - ' indices and the *step* or stride length of the slice. Missing ' - 'or\n' - ' out-of-bounds indices are handled in a manner consistent with\n' - ' regular slices.\n' - '\n' - '\n' - 'Static method objects\n' - '---------------------\n' - '\n' - 'Static method objects provide a way of defeating the transformation ' - 'of\n' - 'function objects to method objects described above. A static ' - 'method\n' - 'object is a wrapper around any other object, usually a ' - 'user-defined\n' - 'method object. When a static method object is retrieved from a ' - 'class\n' - 'or a class instance, the object actually returned is the wrapped\n' - 'object, which is not subject to any further transformation. Static\n' - 'method objects are also callable. Static method objects are created ' - 'by\n' - 'the built-in "staticmethod()" constructor.\n' - '\n' - '\n' - 'Class method objects\n' - '--------------------\n' - '\n' - 'A class method object, like a static method object, is a wrapper\n' - 'around another object that alters the way in which that object is\n' - 'retrieved from classes and class instances. The behaviour of class\n' - 'method objects upon such retrieval is described above, under ' - '“instance\n' - 'methods”. Class method objects are created by the built-in\n' - '"classmethod()" constructor.\n', - 'typesfunctions': 'Functions\n' - '*********\n' - '\n' - 'Function objects are created by function definitions. The ' - 'only\n' - 'operation on a function object is to call it: ' - '"func(argument-list)".\n' - '\n' - 'There are really two flavors of function objects: built-in ' - 'functions\n' - 'and user-defined functions. Both support the same ' - 'operation (to call\n' - 'the function), but the implementation is different, hence ' - 'the\n' - 'different object types.\n' - '\n' - 'See Function definitions for more information.\n', - 'typesmapping': 'Mapping Types — "dict"\n' - '**********************\n' - '\n' - 'A *mapping* object maps *hashable* values to arbitrary ' - 'objects.\n' - 'Mappings are mutable objects. There is currently only one ' - 'standard\n' - 'mapping type, the *dictionary*. (For other containers see ' - 'the built-\n' - 'in "list", "set", and "tuple" classes, and the "collections" ' - 'module.)\n' - '\n' - 'A dictionary’s keys are *almost* arbitrary values. Values ' - 'that are\n' - 'not *hashable*, that is, values containing lists, ' - 'dictionaries or\n' - 'other mutable types (that are compared by value rather than ' - 'by object\n' - 'identity) may not be used as keys. Values that compare equal ' - '(such as\n' - '"1", "1.0", and "True") can be used interchangeably to index ' - 'the same\n' - 'dictionary entry.\n' - '\n' - 'class dict(**kwargs)\n' - 'class dict(mapping, **kwargs)\n' - 'class dict(iterable, **kwargs)\n' - '\n' - ' Return a new dictionary initialized from an optional ' - 'positional\n' - ' argument and a possibly empty set of keyword arguments.\n' - '\n' - ' Dictionaries can be created by several means:\n' - '\n' - ' * Use a comma-separated list of "key: value" pairs within ' - 'braces:\n' - ' "{\'jack\': 4098, \'sjoerd\': 4127}" or "{4098: ' - "'jack', 4127:\n" - ' \'sjoerd\'}"\n' - '\n' - ' * Use a dict comprehension: "{}", "{x: x ** 2 for x in ' - 'range(10)}"\n' - '\n' - ' * Use the type constructor: "dict()", "dict([(\'foo\', ' - "100), ('bar',\n" - ' 200)])", "dict(foo=100, bar=200)"\n' - '\n' - ' If no positional argument is given, an empty dictionary ' - 'is created.\n' - ' If a positional argument is given and it defines a ' - '"keys()" method,\n' - ' a dictionary is created by calling "__getitem__()" on the ' - 'argument\n' - ' with each returned key from the method. Otherwise, the ' - 'positional\n' - ' argument must be an *iterable* object. Each item in the ' - 'iterable\n' - ' must itself be an iterable with exactly two elements. ' - 'The first\n' - ' element of each item becomes a key in the new dictionary, ' - 'and the\n' - ' second element the corresponding value. If a key occurs ' - 'more than\n' - ' once, the last value for that key becomes the ' - 'corresponding value\n' - ' in the new dictionary.\n' - '\n' - ' If keyword arguments are given, the keyword arguments and ' - 'their\n' - ' values are added to the dictionary created from the ' - 'positional\n' - ' argument. If a key being added is already present, the ' - 'value from\n' - ' the keyword argument replaces the value from the ' - 'positional\n' - ' argument.\n' - '\n' - ' To illustrate, the following examples all return a ' - 'dictionary equal\n' - ' to "{"one": 1, "two": 2, "three": 3}":\n' - '\n' - ' >>> a = dict(one=1, two=2, three=3)\n' - " >>> b = {'one': 1, 'two': 2, 'three': 3}\n" - " >>> c = dict(zip(['one', 'two', 'three'], [1, 2, 3]))\n" - " >>> d = dict([('two', 2), ('one', 1), ('three', 3)])\n" - " >>> e = dict({'three': 3, 'one': 1, 'two': 2})\n" - " >>> f = dict({'one': 1, 'three': 3}, two=2)\n" - ' >>> a == b == c == d == e == f\n' - ' True\n' - '\n' - ' Providing keyword arguments as in the first example only ' - 'works for\n' - ' keys that are valid Python identifiers. Otherwise, any ' - 'valid keys\n' - ' can be used.\n' - '\n' - ' These are the operations that dictionaries support (and ' - 'therefore,\n' - ' custom mapping types should support too):\n' - '\n' - ' list(d)\n' - '\n' - ' Return a list of all the keys used in the dictionary ' - '*d*.\n' - '\n' - ' len(d)\n' - '\n' - ' Return the number of items in the dictionary *d*.\n' - '\n' - ' d[key]\n' - '\n' - ' Return the item of *d* with key *key*. Raises a ' - '"KeyError" if\n' - ' *key* is not in the map.\n' - '\n' - ' If a subclass of dict defines a method "__missing__()" ' - 'and *key*\n' - ' is not present, the "d[key]" operation calls that ' - 'method with\n' - ' the key *key* as argument. The "d[key]" operation ' - 'then returns\n' - ' or raises whatever is returned or raised by the\n' - ' "__missing__(key)" call. No other operations or ' - 'methods invoke\n' - ' "__missing__()". If "__missing__()" is not defined, ' - '"KeyError"\n' - ' is raised. "__missing__()" must be a method; it cannot ' - 'be an\n' - ' instance variable:\n' - '\n' - ' >>> class Counter(dict):\n' - ' ... def __missing__(self, key):\n' - ' ... return 0\n' - ' ...\n' - ' >>> c = Counter()\n' - " >>> c['red']\n" - ' 0\n' - " >>> c['red'] += 1\n" - " >>> c['red']\n" - ' 1\n' - '\n' - ' The example above shows part of the implementation of\n' - ' "collections.Counter". A different "__missing__" ' - 'method is used\n' - ' by "collections.defaultdict".\n' - '\n' - ' d[key] = value\n' - '\n' - ' Set "d[key]" to *value*.\n' - '\n' - ' del d[key]\n' - '\n' - ' Remove "d[key]" from *d*. Raises a "KeyError" if ' - '*key* is not\n' - ' in the map.\n' - '\n' - ' key in d\n' - '\n' - ' Return "True" if *d* has a key *key*, else "False".\n' - '\n' - ' key not in d\n' - '\n' - ' Equivalent to "not key in d".\n' - '\n' - ' iter(d)\n' - '\n' - ' Return an iterator over the keys of the dictionary. ' - 'This is a\n' - ' shortcut for "iter(d.keys())".\n' - '\n' - ' clear()\n' - '\n' - ' Remove all items from the dictionary.\n' - '\n' - ' copy()\n' - '\n' - ' Return a shallow copy of the dictionary.\n' - '\n' - ' classmethod fromkeys(iterable, value=None, /)\n' - '\n' - ' Create a new dictionary with keys from *iterable* and ' - 'values set\n' - ' to *value*.\n' - '\n' - ' "fromkeys()" is a class method that returns a new ' - 'dictionary.\n' - ' *value* defaults to "None". All of the values refer ' - 'to just a\n' - ' single instance, so it generally doesn’t make sense ' - 'for *value*\n' - ' to be a mutable object such as an empty list. To get ' - 'distinct\n' - ' values, use a dict comprehension instead.\n' - '\n' - ' get(key, default=None)\n' - '\n' - ' Return the value for *key* if *key* is in the ' - 'dictionary, else\n' - ' *default*. If *default* is not given, it defaults to ' - '"None", so\n' - ' that this method never raises a "KeyError".\n' - '\n' - ' items()\n' - '\n' - ' Return a new view of the dictionary’s items ("(key, ' - 'value)"\n' - ' pairs). See the documentation of view objects.\n' - '\n' - ' keys()\n' - '\n' - ' Return a new view of the dictionary’s keys. See the\n' - ' documentation of view objects.\n' - '\n' - ' pop(key[, default])\n' - '\n' - ' If *key* is in the dictionary, remove it and return ' - 'its value,\n' - ' else return *default*. If *default* is not given and ' - '*key* is\n' - ' not in the dictionary, a "KeyError" is raised.\n' - '\n' - ' popitem()\n' - '\n' - ' Remove and return a "(key, value)" pair from the ' - 'dictionary.\n' - ' Pairs are returned in LIFO (last-in, first-out) ' - 'order.\n' - '\n' - ' "popitem()" is useful to destructively iterate over a\n' - ' dictionary, as often used in set algorithms. If the ' - 'dictionary\n' - ' is empty, calling "popitem()" raises a "KeyError".\n' - '\n' - ' Changed in version 3.7: LIFO order is now guaranteed. ' - 'In prior\n' - ' versions, "popitem()" would return an arbitrary ' - 'key/value pair.\n' - '\n' - ' reversed(d)\n' - '\n' - ' Return a reverse iterator over the keys of the ' - 'dictionary. This\n' - ' is a shortcut for "reversed(d.keys())".\n' - '\n' - ' Added in version 3.8.\n' - '\n' - ' setdefault(key, default=None)\n' - '\n' - ' If *key* is in the dictionary, return its value. If ' - 'not, insert\n' - ' *key* with a value of *default* and return *default*. ' - '*default*\n' - ' defaults to "None".\n' - '\n' - ' update([other])\n' - '\n' - ' Update the dictionary with the key/value pairs from ' - '*other*,\n' - ' overwriting existing keys. Return "None".\n' - '\n' - ' "update()" accepts either another object with a ' - '"keys()" method\n' - ' (in which case "__getitem__()" is called with every ' - 'key returned\n' - ' from the method) or an iterable of key/value pairs (as ' - 'tuples or\n' - ' other iterables of length two). If keyword arguments ' - 'are\n' - ' specified, the dictionary is then updated with those ' - 'key/value\n' - ' pairs: "d.update(red=1, blue=2)".\n' - '\n' - ' values()\n' - '\n' - ' Return a new view of the dictionary’s values. See ' - 'the\n' - ' documentation of view objects.\n' - '\n' - ' An equality comparison between one "dict.values()" ' - 'view and\n' - ' another will always return "False". This also applies ' - 'when\n' - ' comparing "dict.values()" to itself:\n' - '\n' - " >>> d = {'a': 1}\n" - ' >>> d.values() == d.values()\n' - ' False\n' - '\n' - ' d | other\n' - '\n' - ' Create a new dictionary with the merged keys and ' - 'values of *d*\n' - ' and *other*, which must both be dictionaries. The ' - 'values of\n' - ' *other* take priority when *d* and *other* share ' - 'keys.\n' - '\n' - ' Added in version 3.9.\n' - '\n' - ' d |= other\n' - '\n' - ' Update the dictionary *d* with keys and values from ' - '*other*,\n' - ' which may be either a *mapping* or an *iterable* of ' - 'key/value\n' - ' pairs. The values of *other* take priority when *d* ' - 'and *other*\n' - ' share keys.\n' - '\n' - ' Added in version 3.9.\n' - '\n' - ' Dictionaries compare equal if and only if they have the ' - 'same "(key,\n' - ' value)" pairs (regardless of ordering). Order comparisons ' - '(‘<’,\n' - ' ‘<=’, ‘>=’, ‘>’) raise "TypeError".\n' - '\n' - ' Dictionaries preserve insertion order. Note that ' - 'updating a key\n' - ' does not affect the order. Keys added after deletion are ' - 'inserted\n' - ' at the end.\n' - '\n' - ' >>> d = {"one": 1, "two": 2, "three": 3, "four": 4}\n' - ' >>> d\n' - " {'one': 1, 'two': 2, 'three': 3, 'four': 4}\n" - ' >>> list(d)\n' - " ['one', 'two', 'three', 'four']\n" - ' >>> list(d.values())\n' - ' [1, 2, 3, 4]\n' - ' >>> d["one"] = 42\n' - ' >>> d\n' - " {'one': 42, 'two': 2, 'three': 3, 'four': 4}\n" - ' >>> del d["two"]\n' - ' >>> d["two"] = None\n' - ' >>> d\n' - " {'one': 42, 'three': 3, 'four': 4, 'two': None}\n" - '\n' - ' Changed in version 3.7: Dictionary order is guaranteed to ' - 'be\n' - ' insertion order. This behavior was an implementation ' - 'detail of\n' - ' CPython from 3.6.\n' - '\n' - ' Dictionaries and dictionary views are reversible.\n' - '\n' - ' >>> d = {"one": 1, "two": 2, "three": 3, "four": 4}\n' - ' >>> d\n' - " {'one': 1, 'two': 2, 'three': 3, 'four': 4}\n" - ' >>> list(reversed(d))\n' - " ['four', 'three', 'two', 'one']\n" - ' >>> list(reversed(d.values()))\n' - ' [4, 3, 2, 1]\n' - ' >>> list(reversed(d.items()))\n' - " [('four', 4), ('three', 3), ('two', 2), ('one', 1)]\n" - '\n' - ' Changed in version 3.8: Dictionaries are now reversible.\n' - '\n' - 'See also:\n' - '\n' - ' "types.MappingProxyType" can be used to create a read-only ' - 'view of a\n' - ' "dict".\n' - '\n' - '\n' - 'Dictionary view objects\n' - '=======================\n' - '\n' - 'The objects returned by "dict.keys()", "dict.values()" and\n' - '"dict.items()" are *view objects*. They provide a dynamic ' - 'view on the\n' - 'dictionary’s entries, which means that when the dictionary ' - 'changes,\n' - 'the view reflects these changes.\n' - '\n' - 'Dictionary views can be iterated over to yield their ' - 'respective data,\n' - 'and support membership tests:\n' - '\n' - 'len(dictview)\n' - '\n' - ' Return the number of entries in the dictionary.\n' - '\n' - 'iter(dictview)\n' - '\n' - ' Return an iterator over the keys, values or items ' - '(represented as\n' - ' tuples of "(key, value)") in the dictionary.\n' - '\n' - ' Keys and values are iterated over in insertion order. ' - 'This allows\n' - ' the creation of "(value, key)" pairs using "zip()": ' - '"pairs =\n' - ' zip(d.values(), d.keys())". Another way to create the ' - 'same list is\n' - ' "pairs = [(v, k) for (k, v) in d.items()]".\n' - '\n' - ' Iterating views while adding or deleting entries in the ' - 'dictionary\n' - ' may raise a "RuntimeError" or fail to iterate over all ' - 'entries.\n' - '\n' - ' Changed in version 3.7: Dictionary order is guaranteed to ' - 'be\n' - ' insertion order.\n' - '\n' - 'x in dictview\n' - '\n' - ' Return "True" if *x* is in the underlying dictionary’s ' - 'keys, values\n' - ' or items (in the latter case, *x* should be a "(key, ' - 'value)"\n' - ' tuple).\n' - '\n' - 'reversed(dictview)\n' - '\n' - ' Return a reverse iterator over the keys, values or items ' - 'of the\n' - ' dictionary. The view will be iterated in reverse order of ' - 'the\n' - ' insertion.\n' - '\n' - ' Changed in version 3.8: Dictionary views are now ' - 'reversible.\n' - '\n' - 'dictview.mapping\n' - '\n' - ' Return a "types.MappingProxyType" that wraps the ' - 'original\n' - ' dictionary to which the view refers.\n' - '\n' - ' Added in version 3.10.\n' - '\n' - 'Keys views are set-like since their entries are unique and ' - '*hashable*.\n' - 'Items views also have set-like operations since the (key, ' - 'value) pairs\n' - 'are unique and the keys are hashable. If all values in an ' - 'items view\n' - 'are hashable as well, then the items view can interoperate ' - 'with other\n' - 'sets. (Values views are not treated as set-like since the ' - 'entries are\n' - 'generally not unique.) For set-like views, all of the ' - 'operations\n' - 'defined for the abstract base class "collections.abc.Set" ' - 'are\n' - 'available (for example, "==", "<", or "^"). While using ' - 'set\n' - 'operators, set-like views accept any iterable as the other ' - 'operand,\n' - 'unlike sets which only accept sets as the input.\n' - '\n' - 'An example of dictionary view usage:\n' - '\n' - " >>> dishes = {'eggs': 2, 'sausage': 1, 'bacon': 1, " - "'spam': 500}\n" - ' >>> keys = dishes.keys()\n' - ' >>> values = dishes.values()\n' - '\n' - ' >>> # iteration\n' - ' >>> n = 0\n' - ' >>> for val in values:\n' - ' ... n += val\n' - ' ...\n' - ' >>> print(n)\n' - ' 504\n' - '\n' - ' >>> # keys and values are iterated over in the same order ' - '(insertion order)\n' - ' >>> list(keys)\n' - " ['eggs', 'sausage', 'bacon', 'spam']\n" - ' >>> list(values)\n' - ' [2, 1, 1, 500]\n' - '\n' - ' >>> # view objects are dynamic and reflect dict changes\n' - " >>> del dishes['eggs']\n" - " >>> del dishes['sausage']\n" - ' >>> list(keys)\n' - " ['bacon', 'spam']\n" - '\n' - ' >>> # set operations\n' - " >>> keys & {'eggs', 'bacon', 'salad'}\n" - " {'bacon'}\n" - " >>> keys ^ {'sausage', 'juice'} == {'juice', 'sausage', " - "'bacon', 'spam'}\n" - ' True\n' - " >>> keys | ['juice', 'juice', 'juice'] == {'bacon', " - "'spam', 'juice'}\n" - ' True\n' - '\n' - ' >>> # get back a read-only proxy for the original ' - 'dictionary\n' - ' >>> values.mapping\n' - " mappingproxy({'bacon': 1, 'spam': 500})\n" - " >>> values.mapping['spam']\n" - ' 500\n', - 'typesmethods': 'Methods\n' - '*******\n' - '\n' - 'Methods are functions that are called using the attribute ' - 'notation.\n' - 'There are two flavors: built-in methods (such as "append()" ' - 'on lists)\n' - 'and class instance method. Built-in methods are described ' - 'with the\n' - 'types that support them.\n' - '\n' - 'If you access a method (a function defined in a class ' - 'namespace)\n' - 'through an instance, you get a special object: a *bound ' - 'method* (also\n' - 'called instance method) object. When called, it will add the ' - '"self"\n' - 'argument to the argument list. Bound methods have two ' - 'special read-\n' - 'only attributes: "m.__self__" is the object on which the ' - 'method\n' - 'operates, and "m.__func__" is the function implementing the ' - 'method.\n' - 'Calling "m(arg-1, arg-2, ..., arg-n)" is completely ' - 'equivalent to\n' - 'calling "m.__func__(m.__self__, arg-1, arg-2, ..., arg-n)".\n' - '\n' - 'Like function objects, bound method objects support getting ' - 'arbitrary\n' - 'attributes. However, since method attributes are actually ' - 'stored on\n' - 'the underlying function object ("method.__func__"), setting ' - 'method\n' - 'attributes on bound methods is disallowed. Attempting to ' - 'set an\n' - 'attribute on a method results in an "AttributeError" being ' - 'raised. In\n' - 'order to set a method attribute, you need to explicitly set ' - 'it on the\n' - 'underlying function object:\n' - '\n' - ' >>> class C:\n' - ' ... def method(self):\n' - ' ... pass\n' - ' ...\n' - ' >>> c = C()\n' - " >>> c.method.whoami = 'my name is method' # can't set on " - 'the method\n' - ' Traceback (most recent call last):\n' - ' File "<stdin>", line 1, in <module>\n' - " AttributeError: 'method' object has no attribute " - "'whoami'\n" - " >>> c.method.__func__.whoami = 'my name is method'\n" - ' >>> c.method.whoami\n' - " 'my name is method'\n" - '\n' - 'See Instance methods for more information.\n', - 'typesmodules': 'Modules\n' - '*******\n' - '\n' - 'The only special operation on a module is attribute access: ' - '"m.name",\n' - 'where *m* is a module and *name* accesses a name defined in ' - '*m*’s\n' - 'symbol table. Module attributes can be assigned to. (Note ' - 'that the\n' - '"import" statement is not, strictly speaking, an operation ' - 'on a module\n' - 'object; "import foo" does not require a module object named ' - '*foo* to\n' - 'exist, rather it requires an (external) *definition* for a ' - 'module\n' - 'named *foo* somewhere.)\n' - '\n' - 'A special attribute of every module is "__dict__". This is ' - 'the\n' - 'dictionary containing the module’s symbol table. Modifying ' - 'this\n' - 'dictionary will actually change the module’s symbol table, ' - 'but direct\n' - 'assignment to the "__dict__" attribute is not possible (you ' - 'can write\n' - '"m.__dict__[\'a\'] = 1", which defines "m.a" to be "1", but ' - 'you can’t\n' - 'write "m.__dict__ = {}"). Modifying "__dict__" directly is ' - 'not\n' - 'recommended.\n' - '\n' - 'Modules built into the interpreter are written like this: ' - '"<module\n' - '\'sys\' (built-in)>". If loaded from a file, they are ' - 'written as\n' - '"<module \'os\' from ' - '\'/usr/local/lib/pythonX.Y/os.pyc\'>".\n', - 'typesseq': 'Sequence Types — "list", "tuple", "range"\n' - '*****************************************\n' - '\n' - 'There are three basic sequence types: lists, tuples, and range\n' - 'objects. Additional sequence types tailored for processing of ' - 'binary\n' - 'data and text strings are described in dedicated sections.\n' - '\n' - '\n' - 'Common Sequence Operations\n' - '==========================\n' - '\n' - 'The operations in the following table are supported by most ' - 'sequence\n' - 'types, both mutable and immutable. The ' - '"collections.abc.Sequence" ABC\n' - 'is provided to make it easier to correctly implement these ' - 'operations\n' - 'on custom sequence types.\n' - '\n' - 'This table lists the sequence operations sorted in ascending ' - 'priority.\n' - 'In the table, *s* and *t* are sequences of the same type, *n*, ' - '*i*,\n' - '*j* and *k* are integers and *x* is an arbitrary object that ' - 'meets any\n' - 'type and value restrictions imposed by *s*.\n' - '\n' - 'The "in" and "not in" operations have the same priorities as ' - 'the\n' - 'comparison operations. The "+" (concatenation) and "*" ' - '(repetition)\n' - 'operations have the same priority as the corresponding numeric\n' - 'operations. [3]\n' - '\n' - '+----------------------------+----------------------------------+------------+\n' - '| Operation | Result ' - '| Notes |\n' - '|============================|==================================|============|\n' - '| "x in s" | "True" if an item of *s* is ' - '| (1) |\n' - '| | equal to *x*, else "False" ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "x not in s" | "False" if an item of *s* is ' - '| (1) |\n' - '| | equal to *x*, else "True" ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "s + t" | the concatenation of *s* and *t* ' - '| (6)(7) |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "s * n" or "n * s" | equivalent to adding *s* to ' - '| (2)(7) |\n' - '| | itself *n* times ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "s[i]" | *i*th item of *s*, origin 0 ' - '| (3) |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "s[i:j]" | slice of *s* from *i* to *j* ' - '| (3)(4) |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "s[i:j:k]" | slice of *s* from *i* to *j* ' - '| (3)(5) |\n' - '| | with step *k* ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "len(s)" | length of *s* ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "min(s)" | smallest item of *s* ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "max(s)" | largest item of *s* ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "s.index(x[, i[, j]])" | index of the first occurrence of ' - '| (8) |\n' - '| | *x* in *s* (at or after index ' - '| |\n' - '| | *i* and before index *j*) ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '| "s.count(x)" | total number of occurrences of ' - '| |\n' - '| | *x* in *s* ' - '| |\n' - '+----------------------------+----------------------------------+------------+\n' - '\n' - 'Sequences of the same type also support comparisons. In ' - 'particular,\n' - 'tuples and lists are compared lexicographically by comparing\n' - 'corresponding elements. This means that to compare equal, every\n' - 'element must compare equal and the two sequences must be of the ' - 'same\n' - 'type and have the same length. (For full details see ' - 'Comparisons in\n' - 'the language reference.)\n' - '\n' - 'Forward and reversed iterators over mutable sequences access ' - 'values\n' - 'using an index. That index will continue to march forward (or\n' - 'backward) even if the underlying sequence is mutated. The ' - 'iterator\n' - 'terminates only when an "IndexError" or a "StopIteration" is\n' - 'encountered (or when the index drops below zero).\n' - '\n' - 'Notes:\n' - '\n' - '1. While the "in" and "not in" operations are used only for ' - 'simple\n' - ' containment testing in the general case, some specialised ' - 'sequences\n' - ' (such as "str", "bytes" and "bytearray") also use them for\n' - ' subsequence testing:\n' - '\n' - ' >>> "gg" in "eggs"\n' - ' True\n' - '\n' - '2. Values of *n* less than "0" are treated as "0" (which yields ' - 'an\n' - ' empty sequence of the same type as *s*). Note that items in ' - 'the\n' - ' sequence *s* are not copied; they are referenced multiple ' - 'times.\n' - ' This often haunts new Python programmers; consider:\n' - '\n' - ' >>> lists = [[]] * 3\n' - ' >>> lists\n' - ' [[], [], []]\n' - ' >>> lists[0].append(3)\n' - ' >>> lists\n' - ' [[3], [3], [3]]\n' - '\n' - ' What has happened is that "[[]]" is a one-element list ' - 'containing\n' - ' an empty list, so all three elements of "[[]] * 3" are ' - 'references\n' - ' to this single empty list. Modifying any of the elements of\n' - ' "lists" modifies this single list. You can create a list of\n' - ' different lists this way:\n' - '\n' - ' >>> lists = [[] for i in range(3)]\n' - ' >>> lists[0].append(3)\n' - ' >>> lists[1].append(5)\n' - ' >>> lists[2].append(7)\n' - ' >>> lists\n' - ' [[3], [5], [7]]\n' - '\n' - ' Further explanation is available in the FAQ entry How do I ' - 'create a\n' - ' multidimensional list?.\n' - '\n' - '3. If *i* or *j* is negative, the index is relative to the end ' - 'of\n' - ' sequence *s*: "len(s) + i" or "len(s) + j" is substituted. ' - 'But\n' - ' note that "-0" is still "0".\n' - '\n' - '4. The slice of *s* from *i* to *j* is defined as the sequence ' - 'of\n' - ' items with index *k* such that "i <= k < j". If *i* or *j* ' - 'is\n' - ' greater than "len(s)", use "len(s)". If *i* is omitted or ' - '"None",\n' - ' use "0". If *j* is omitted or "None", use "len(s)". If *i* ' - 'is\n' - ' greater than or equal to *j*, the slice is empty.\n' - '\n' - '5. The slice of *s* from *i* to *j* with step *k* is defined as ' - 'the\n' - ' sequence of items with index "x = i + n*k" such that "0 <= n ' - '<\n' - ' (j-i)/k". In other words, the indices are "i", "i+k", ' - '"i+2*k",\n' - ' "i+3*k" and so on, stopping when *j* is reached (but never\n' - ' including *j*). When *k* is positive, *i* and *j* are ' - 'reduced to\n' - ' "len(s)" if they are greater. When *k* is negative, *i* and ' - '*j* are\n' - ' reduced to "len(s) - 1" if they are greater. If *i* or *j* ' - 'are\n' - ' omitted or "None", they become “end” values (which end ' - 'depends on\n' - ' the sign of *k*). Note, *k* cannot be zero. If *k* is ' - '"None", it\n' - ' is treated like "1".\n' - '\n' - '6. Concatenating immutable sequences always results in a new ' - 'object.\n' - ' This means that building up a sequence by repeated ' - 'concatenation\n' - ' will have a quadratic runtime cost in the total sequence ' - 'length.\n' - ' To get a linear runtime cost, you must switch to one of the\n' - ' alternatives below:\n' - '\n' - ' * if concatenating "str" objects, you can build a list and ' - 'use\n' - ' "str.join()" at the end or else write to an "io.StringIO"\n' - ' instance and retrieve its value when complete\n' - '\n' - ' * if concatenating "bytes" objects, you can similarly use\n' - ' "bytes.join()" or "io.BytesIO", or you can do in-place\n' - ' concatenation with a "bytearray" object. "bytearray" ' - 'objects are\n' - ' mutable and have an efficient overallocation mechanism\n' - '\n' - ' * if concatenating "tuple" objects, extend a "list" instead\n' - '\n' - ' * for other types, investigate the relevant class ' - 'documentation\n' - '\n' - '7. Some sequence types (such as "range") only support item ' - 'sequences\n' - ' that follow specific patterns, and hence don’t support ' - 'sequence\n' - ' concatenation or repetition.\n' - '\n' - '8. "index" raises "ValueError" when *x* is not found in *s*. Not ' - 'all\n' - ' implementations support passing the additional arguments *i* ' - 'and\n' - ' *j*. These arguments allow efficient searching of subsections ' - 'of\n' - ' the sequence. Passing the extra arguments is roughly ' - 'equivalent to\n' - ' using "s[i:j].index(x)", only without copying any data and ' - 'with the\n' - ' returned index being relative to the start of the sequence ' - 'rather\n' - ' than the start of the slice.\n' - '\n' - '\n' - 'Immutable Sequence Types\n' - '========================\n' - '\n' - 'The only operation that immutable sequence types generally ' - 'implement\n' - 'that is not also implemented by mutable sequence types is ' - 'support for\n' - 'the "hash()" built-in.\n' - '\n' - 'This support allows immutable sequences, such as "tuple" ' - 'instances, to\n' - 'be used as "dict" keys and stored in "set" and "frozenset" ' - 'instances.\n' - '\n' - 'Attempting to hash an immutable sequence that contains ' - 'unhashable\n' - 'values will result in "TypeError".\n' - '\n' - '\n' - 'Mutable Sequence Types\n' - '======================\n' - '\n' - 'The operations in the following table are defined on mutable ' - 'sequence\n' - 'types. The "collections.abc.MutableSequence" ABC is provided to ' - 'make\n' - 'it easier to correctly implement these operations on custom ' - 'sequence\n' - 'types.\n' - '\n' - 'In the table *s* is an instance of a mutable sequence type, *t* ' - 'is any\n' - 'iterable object and *x* is an arbitrary object that meets any ' - 'type and\n' - 'value restrictions imposed by *s* (for example, "bytearray" ' - 'only\n' - 'accepts integers that meet the value restriction "0 <= x <= ' - '255").\n' - '\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| Operation | ' - 'Result | Notes |\n' - '|================================|==================================|=======================|\n' - '| "s[i] = x" | item *i* of *s* is replaced ' - 'by | |\n' - '| | ' - '*x* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s[i:j] = t" | slice of *s* from *i* to *j* ' - 'is | |\n' - '| | replaced by the contents of ' - 'the | |\n' - '| | iterable ' - '*t* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "del s[i:j]" | same as "s[i:j] = ' - '[]" | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s[i:j:k] = t" | the elements of "s[i:j:k]" ' - 'are | (1) |\n' - '| | replaced by those of ' - '*t* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "del s[i:j:k]" | removes the elements ' - 'of | |\n' - '| | "s[i:j:k]" from the ' - 'list | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.append(x)" | appends *x* to the end of ' - 'the | |\n' - '| | sequence (same ' - 'as | |\n' - '| | "s[len(s):len(s)] = ' - '[x]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.clear()" | removes all items from *s* ' - '(same | (5) |\n' - '| | as "del ' - 's[:]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.copy()" | creates a shallow copy of ' - '*s* | (5) |\n' - '| | (same as ' - '"s[:]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.extend(t)" or "s += t" | extends *s* with the contents ' - 'of | |\n' - '| | *t* (for the most part the ' - 'same | |\n' - '| | as "s[len(s):len(s)] = ' - 't") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s *= n" | updates *s* with its ' - 'contents | (6) |\n' - '| | repeated *n* ' - 'times | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.insert(i, x)" | inserts *x* into *s* at ' - 'the | |\n' - '| | index given by *i* (same ' - 'as | |\n' - '| | "s[i:i] = ' - '[x]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.pop()" or "s.pop(i)" | retrieves the item at *i* ' - 'and | (2) |\n' - '| | also removes it from ' - '*s* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.remove(x)" | removes the first item from ' - '*s* | (3) |\n' - '| | where "s[i]" is equal to ' - '*x* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.reverse()" | reverses the items of *s* ' - 'in | (4) |\n' - '| | ' - 'place | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '\n' - 'Notes:\n' - '\n' - '1. If *k* is not equal to "1", *t* must have the same length as ' - 'the\n' - ' slice it is replacing.\n' - '\n' - '2. The optional argument *i* defaults to "-1", so that by ' - 'default the\n' - ' last item is removed and returned.\n' - '\n' - '3. "remove()" raises "ValueError" when *x* is not found in *s*.\n' - '\n' - '4. The "reverse()" method modifies the sequence in place for ' - 'economy\n' - ' of space when reversing a large sequence. To remind users ' - 'that it\n' - ' operates by side effect, it does not return the reversed ' - 'sequence.\n' - '\n' - '5. "clear()" and "copy()" are included for consistency with the\n' - ' interfaces of mutable containers that don’t support slicing\n' - ' operations (such as "dict" and "set"). "copy()" is not part ' - 'of the\n' - ' "collections.abc.MutableSequence" ABC, but most concrete ' - 'mutable\n' - ' sequence classes provide it.\n' - '\n' - ' Added in version 3.3: "clear()" and "copy()" methods.\n' - '\n' - '6. The value *n* is an integer, or an object implementing\n' - ' "__index__()". Zero and negative values of *n* clear the ' - 'sequence.\n' - ' Items in the sequence are not copied; they are referenced ' - 'multiple\n' - ' times, as explained for "s * n" under Common Sequence ' - 'Operations.\n' - '\n' - '\n' - 'Lists\n' - '=====\n' - '\n' - 'Lists are mutable sequences, typically used to store collections ' - 'of\n' - 'homogeneous items (where the precise degree of similarity will ' - 'vary by\n' - 'application).\n' - '\n' - 'class list([iterable])\n' - '\n' - ' Lists may be constructed in several ways:\n' - '\n' - ' * Using a pair of square brackets to denote the empty list: ' - '"[]"\n' - '\n' - ' * Using square brackets, separating items with commas: "[a]", ' - '"[a,\n' - ' b, c]"\n' - '\n' - ' * Using a list comprehension: "[x for x in iterable]"\n' - '\n' - ' * Using the type constructor: "list()" or "list(iterable)"\n' - '\n' - ' The constructor builds a list whose items are the same and in ' - 'the\n' - ' same order as *iterable*’s items. *iterable* may be either ' - 'a\n' - ' sequence, a container that supports iteration, or an ' - 'iterator\n' - ' object. If *iterable* is already a list, a copy is made and\n' - ' returned, similar to "iterable[:]". For example, ' - '"list(\'abc\')"\n' - ' returns "[\'a\', \'b\', \'c\']" and "list( (1, 2, 3) )" ' - 'returns "[1, 2,\n' - ' 3]". If no argument is given, the constructor creates a new ' - 'empty\n' - ' list, "[]".\n' - '\n' - ' Many other operations also produce lists, including the ' - '"sorted()"\n' - ' built-in.\n' - '\n' - ' Lists implement all of the common and mutable sequence ' - 'operations.\n' - ' Lists also provide the following additional method:\n' - '\n' - ' sort(*, key=None, reverse=False)\n' - '\n' - ' This method sorts the list in place, using only "<" ' - 'comparisons\n' - ' between items. Exceptions are not suppressed - if any ' - 'comparison\n' - ' operations fail, the entire sort operation will fail (and ' - 'the\n' - ' list will likely be left in a partially modified state).\n' - '\n' - ' "sort()" accepts two arguments that can only be passed by\n' - ' keyword (keyword-only arguments):\n' - '\n' - ' *key* specifies a function of one argument that is used ' - 'to\n' - ' extract a comparison key from each list element (for ' - 'example,\n' - ' "key=str.lower"). The key corresponding to each item in ' - 'the list\n' - ' is calculated once and then used for the entire sorting ' - 'process.\n' - ' The default value of "None" means that list items are ' - 'sorted\n' - ' directly without calculating a separate key value.\n' - '\n' - ' The "functools.cmp_to_key()" utility is available to ' - 'convert a\n' - ' 2.x style *cmp* function to a *key* function.\n' - '\n' - ' *reverse* is a boolean value. If set to "True", then the ' - 'list\n' - ' elements are sorted as if each comparison were reversed.\n' - '\n' - ' This method modifies the sequence in place for economy of ' - 'space\n' - ' when sorting a large sequence. To remind users that it ' - 'operates\n' - ' by side effect, it does not return the sorted sequence ' - '(use\n' - ' "sorted()" to explicitly request a new sorted list ' - 'instance).\n' - '\n' - ' The "sort()" method is guaranteed to be stable. A sort ' - 'is\n' - ' stable if it guarantees not to change the relative order ' - 'of\n' - ' elements that compare equal — this is helpful for sorting ' - 'in\n' - ' multiple passes (for example, sort by department, then by ' - 'salary\n' - ' grade).\n' - '\n' - ' For sorting examples and a brief sorting tutorial, see ' - 'Sorting\n' - ' Techniques.\n' - '\n' - ' **CPython implementation detail:** While a list is being ' - 'sorted,\n' - ' the effect of attempting to mutate, or even inspect, the ' - 'list is\n' - ' undefined. The C implementation of Python makes the list ' - 'appear\n' - ' empty for the duration, and raises "ValueError" if it can ' - 'detect\n' - ' that the list has been mutated during a sort.\n' - '\n' - '\n' - 'Tuples\n' - '======\n' - '\n' - 'Tuples are immutable sequences, typically used to store ' - 'collections of\n' - 'heterogeneous data (such as the 2-tuples produced by the ' - '"enumerate()"\n' - 'built-in). Tuples are also used for cases where an immutable ' - 'sequence\n' - 'of homogeneous data is needed (such as allowing storage in a ' - '"set" or\n' - '"dict" instance).\n' - '\n' - 'class tuple([iterable])\n' - '\n' - ' Tuples may be constructed in a number of ways:\n' - '\n' - ' * Using a pair of parentheses to denote the empty tuple: ' - '"()"\n' - '\n' - ' * Using a trailing comma for a singleton tuple: "a," or ' - '"(a,)"\n' - '\n' - ' * Separating items with commas: "a, b, c" or "(a, b, c)"\n' - '\n' - ' * Using the "tuple()" built-in: "tuple()" or ' - '"tuple(iterable)"\n' - '\n' - ' The constructor builds a tuple whose items are the same and ' - 'in the\n' - ' same order as *iterable*’s items. *iterable* may be either ' - 'a\n' - ' sequence, a container that supports iteration, or an ' - 'iterator\n' - ' object. If *iterable* is already a tuple, it is returned\n' - ' unchanged. For example, "tuple(\'abc\')" returns "(\'a\', ' - '\'b\', \'c\')"\n' - ' and "tuple( [1, 2, 3] )" returns "(1, 2, 3)". If no argument ' - 'is\n' - ' given, the constructor creates a new empty tuple, "()".\n' - '\n' - ' Note that it is actually the comma which makes a tuple, not ' - 'the\n' - ' parentheses. The parentheses are optional, except in the ' - 'empty\n' - ' tuple case, or when they are needed to avoid syntactic ' - 'ambiguity.\n' - ' For example, "f(a, b, c)" is a function call with three ' - 'arguments,\n' - ' while "f((a, b, c))" is a function call with a 3-tuple as the ' - 'sole\n' - ' argument.\n' - '\n' - ' Tuples implement all of the common sequence operations.\n' - '\n' - 'For heterogeneous collections of data where access by name is ' - 'clearer\n' - 'than access by index, "collections.namedtuple()" may be a more\n' - 'appropriate choice than a simple tuple object.\n' - '\n' - '\n' - 'Ranges\n' - '======\n' - '\n' - 'The "range" type represents an immutable sequence of numbers and ' - 'is\n' - 'commonly used for looping a specific number of times in "for" ' - 'loops.\n' - '\n' - 'class range(stop)\n' - 'class range(start, stop[, step])\n' - '\n' - ' The arguments to the range constructor must be integers ' - '(either\n' - ' built-in "int" or any object that implements the ' - '"__index__()"\n' - ' special method). If the *step* argument is omitted, it ' - 'defaults to\n' - ' "1". If the *start* argument is omitted, it defaults to "0". ' - 'If\n' - ' *step* is zero, "ValueError" is raised.\n' - '\n' - ' For a positive *step*, the contents of a range "r" are ' - 'determined\n' - ' by the formula "r[i] = start + step*i" where "i >= 0" and ' - '"r[i] <\n' - ' stop".\n' - '\n' - ' For a negative *step*, the contents of the range are still\n' - ' determined by the formula "r[i] = start + step*i", but the\n' - ' constraints are "i >= 0" and "r[i] > stop".\n' - '\n' - ' A range object will be empty if "r[0]" does not meet the ' - 'value\n' - ' constraint. Ranges do support negative indices, but these ' - 'are\n' - ' interpreted as indexing from the end of the sequence ' - 'determined by\n' - ' the positive indices.\n' - '\n' - ' Ranges containing absolute values larger than "sys.maxsize" ' - 'are\n' - ' permitted but some features (such as "len()") may raise\n' - ' "OverflowError".\n' - '\n' - ' Range examples:\n' - '\n' - ' >>> list(range(10))\n' - ' [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]\n' - ' >>> list(range(1, 11))\n' - ' [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]\n' - ' >>> list(range(0, 30, 5))\n' - ' [0, 5, 10, 15, 20, 25]\n' - ' >>> list(range(0, 10, 3))\n' - ' [0, 3, 6, 9]\n' - ' >>> list(range(0, -10, -1))\n' - ' [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]\n' - ' >>> list(range(0))\n' - ' []\n' - ' >>> list(range(1, 0))\n' - ' []\n' - '\n' - ' Ranges implement all of the common sequence operations ' - 'except\n' - ' concatenation and repetition (due to the fact that range ' - 'objects\n' - ' can only represent sequences that follow a strict pattern ' - 'and\n' - ' repetition and concatenation will usually violate that ' - 'pattern).\n' - '\n' - ' start\n' - '\n' - ' The value of the *start* parameter (or "0" if the ' - 'parameter was\n' - ' not supplied)\n' - '\n' - ' stop\n' - '\n' - ' The value of the *stop* parameter\n' - '\n' - ' step\n' - '\n' - ' The value of the *step* parameter (or "1" if the parameter ' - 'was\n' - ' not supplied)\n' - '\n' - 'The advantage of the "range" type over a regular "list" or ' - '"tuple" is\n' - 'that a "range" object will always take the same (small) amount ' - 'of\n' - 'memory, no matter the size of the range it represents (as it ' - 'only\n' - 'stores the "start", "stop" and "step" values, calculating ' - 'individual\n' - 'items and subranges as needed).\n' - '\n' - 'Range objects implement the "collections.abc.Sequence" ABC, and\n' - 'provide features such as containment tests, element index ' - 'lookup,\n' - 'slicing and support for negative indices (see Sequence Types — ' - 'list,\n' - 'tuple, range):\n' - '\n' - '>>> r = range(0, 20, 2)\n' - '>>> r\n' - 'range(0, 20, 2)\n' - '>>> 11 in r\n' - 'False\n' - '>>> 10 in r\n' - 'True\n' - '>>> r.index(10)\n' - '5\n' - '>>> r[5]\n' - '10\n' - '>>> r[:5]\n' - 'range(0, 10, 2)\n' - '>>> r[-1]\n' - '18\n' - '\n' - 'Testing range objects for equality with "==" and "!=" compares ' - 'them as\n' - 'sequences. That is, two range objects are considered equal if ' - 'they\n' - 'represent the same sequence of values. (Note that two range ' - 'objects\n' - 'that compare equal might have different "start", "stop" and ' - '"step"\n' - 'attributes, for example "range(0) == range(2, 1, 3)" or ' - '"range(0, 3,\n' - '2) == range(0, 4, 2)".)\n' - '\n' - 'Changed in version 3.2: Implement the Sequence ABC. Support ' - 'slicing\n' - 'and negative indices. Test "int" objects for membership in ' - 'constant\n' - 'time instead of iterating through all items.\n' - '\n' - 'Changed in version 3.3: Define ‘==’ and ‘!=’ to compare range ' - 'objects\n' - 'based on the sequence of values they define (instead of ' - 'comparing\n' - 'based on object identity).Added the "start", "stop" and "step"\n' - 'attributes.\n' - '\n' - 'See also:\n' - '\n' - ' * The linspace recipe shows how to implement a lazy version of ' - 'range\n' - ' suitable for floating-point applications.\n', - 'typesseq-mutable': 'Mutable Sequence Types\n' - '**********************\n' - '\n' - 'The operations in the following table are defined on ' - 'mutable sequence\n' - 'types. The "collections.abc.MutableSequence" ABC is ' - 'provided to make\n' - 'it easier to correctly implement these operations on ' - 'custom sequence\n' - 'types.\n' - '\n' - 'In the table *s* is an instance of a mutable sequence ' - 'type, *t* is any\n' - 'iterable object and *x* is an arbitrary object that ' - 'meets any type and\n' - 'value restrictions imposed by *s* (for example, ' - '"bytearray" only\n' - 'accepts integers that meet the value restriction "0 <= x ' - '<= 255").\n' - '\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| Operation | ' - 'Result | Notes ' - '|\n' - '|================================|==================================|=======================|\n' - '| "s[i] = x" | item *i* of *s* is ' - 'replaced by | |\n' - '| | ' - '*x* | ' - '|\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s[i:j] = t" | slice of *s* from *i* ' - 'to *j* is | |\n' - '| | replaced by the ' - 'contents of the | |\n' - '| | iterable ' - '*t* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "del s[i:j]" | same as "s[i:j] = ' - '[]" | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s[i:j:k] = t" | the elements of ' - '"s[i:j:k]" are | (1) |\n' - '| | replaced by those of ' - '*t* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "del s[i:j:k]" | removes the elements ' - 'of | |\n' - '| | "s[i:j:k]" from the ' - 'list | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.append(x)" | appends *x* to the ' - 'end of the | |\n' - '| | sequence (same ' - 'as | |\n' - '| | "s[len(s):len(s)] = ' - '[x]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.clear()" | removes all items ' - 'from *s* (same | (5) |\n' - '| | as "del ' - 's[:]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.copy()" | creates a shallow ' - 'copy of *s* | (5) |\n' - '| | (same as ' - '"s[:]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.extend(t)" or "s += t" | extends *s* with the ' - 'contents of | |\n' - '| | *t* (for the most ' - 'part the same | |\n' - '| | as "s[len(s):len(s)] ' - '= t") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s *= n" | updates *s* with its ' - 'contents | (6) |\n' - '| | repeated *n* ' - 'times | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.insert(i, x)" | inserts *x* into *s* ' - 'at the | |\n' - '| | index given by *i* ' - '(same as | |\n' - '| | "s[i:i] = ' - '[x]") | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.pop()" or "s.pop(i)" | retrieves the item at ' - '*i* and | (2) |\n' - '| | also removes it from ' - '*s* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.remove(x)" | removes the first ' - 'item from *s* | (3) |\n' - '| | where "s[i]" is equal ' - 'to *x* | |\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '| "s.reverse()" | reverses the items of ' - '*s* in | (4) |\n' - '| | ' - 'place | ' - '|\n' - '+--------------------------------+----------------------------------+-----------------------+\n' - '\n' - 'Notes:\n' - '\n' - '1. If *k* is not equal to "1", *t* must have the same ' - 'length as the\n' - ' slice it is replacing.\n' - '\n' - '2. The optional argument *i* defaults to "-1", so that ' - 'by default the\n' - ' last item is removed and returned.\n' - '\n' - '3. "remove()" raises "ValueError" when *x* is not found ' - 'in *s*.\n' - '\n' - '4. The "reverse()" method modifies the sequence in place ' - 'for economy\n' - ' of space when reversing a large sequence. To remind ' - 'users that it\n' - ' operates by side effect, it does not return the ' - 'reversed sequence.\n' - '\n' - '5. "clear()" and "copy()" are included for consistency ' - 'with the\n' - ' interfaces of mutable containers that don’t support ' - 'slicing\n' - ' operations (such as "dict" and "set"). "copy()" is ' - 'not part of the\n' - ' "collections.abc.MutableSequence" ABC, but most ' - 'concrete mutable\n' - ' sequence classes provide it.\n' - '\n' - ' Added in version 3.3: "clear()" and "copy()" ' - 'methods.\n' - '\n' - '6. The value *n* is an integer, or an object ' - 'implementing\n' - ' "__index__()". Zero and negative values of *n* clear ' - 'the sequence.\n' - ' Items in the sequence are not copied; they are ' - 'referenced multiple\n' - ' times, as explained for "s * n" under Common Sequence ' - 'Operations.\n', - 'unary': 'Unary arithmetic and bitwise operations\n' - '***************************************\n' - '\n' - 'All unary arithmetic and bitwise operations have the same ' - 'priority:\n' - '\n' - ' u_expr ::= power | "-" u_expr | "+" u_expr | "~" u_expr\n' - '\n' - 'The unary "-" (minus) operator yields the negation of its numeric\n' - 'argument; the operation can be overridden with the "__neg__()" ' - 'special\n' - 'method.\n' - '\n' - 'The unary "+" (plus) operator yields its numeric argument ' - 'unchanged;\n' - 'the operation can be overridden with the "__pos__()" special ' - 'method.\n' - '\n' - 'The unary "~" (invert) operator yields the bitwise inversion of ' - 'its\n' - 'integer argument. The bitwise inversion of "x" is defined as\n' - '"-(x+1)". It only applies to integral numbers or to custom ' - 'objects\n' - 'that override the "__invert__()" special method.\n' - '\n' - 'In all three cases, if the argument does not have the proper type, ' - 'a\n' - '"TypeError" exception is raised.\n', - 'while': 'The "while" statement\n' - '*********************\n' - '\n' - 'The "while" statement is used for repeated execution as long as an\n' - 'expression is true:\n' - '\n' - ' while_stmt ::= "while" assignment_expression ":" suite\n' - ' ["else" ":" suite]\n' - '\n' - 'This repeatedly tests the expression and, if it is true, executes ' - 'the\n' - 'first suite; if the expression is false (which may be the first ' - 'time\n' - 'it is tested) the suite of the "else" clause, if present, is ' - 'executed\n' - 'and the loop terminates.\n' - '\n' - 'A "break" statement executed in the first suite terminates the ' - 'loop\n' - 'without executing the "else" clause’s suite. A "continue" ' - 'statement\n' - 'executed in the first suite skips the rest of the suite and goes ' - 'back\n' - 'to testing the expression.\n', - 'with': 'The "with" statement\n' - '********************\n' - '\n' - 'The "with" statement is used to wrap the execution of a block with\n' - 'methods defined by a context manager (see section With Statement\n' - 'Context Managers). This allows common "try"…"except"…"finally" ' - 'usage\n' - 'patterns to be encapsulated for convenient reuse.\n' - '\n' - ' with_stmt ::= "with" ( "(" with_stmt_contents ","? ")" | ' - 'with_stmt_contents ) ":" suite\n' - ' with_stmt_contents ::= with_item ("," with_item)*\n' - ' with_item ::= expression ["as" target]\n' - '\n' - 'The execution of the "with" statement with one “item” proceeds as\n' - 'follows:\n' - '\n' - '1. The context expression (the expression given in the "with_item") ' - 'is\n' - ' evaluated to obtain a context manager.\n' - '\n' - '2. The context manager’s "__enter__()" is loaded for later use.\n' - '\n' - '3. The context manager’s "__exit__()" is loaded for later use.\n' - '\n' - '4. The context manager’s "__enter__()" method is invoked.\n' - '\n' - '5. If a target was included in the "with" statement, the return ' - 'value\n' - ' from "__enter__()" is assigned to it.\n' - '\n' - ' Note:\n' - '\n' - ' The "with" statement guarantees that if the "__enter__()" ' - 'method\n' - ' returns without an error, then "__exit__()" will always be\n' - ' called. Thus, if an error occurs during the assignment to the\n' - ' target list, it will be treated the same as an error occurring\n' - ' within the suite would be. See step 7 below.\n' - '\n' - '6. The suite is executed.\n' - '\n' - '7. The context manager’s "__exit__()" method is invoked. If an\n' - ' exception caused the suite to be exited, its type, value, and\n' - ' traceback are passed as arguments to "__exit__()". Otherwise, ' - 'three\n' - ' "None" arguments are supplied.\n' - '\n' - ' If the suite was exited due to an exception, and the return ' - 'value\n' - ' from the "__exit__()" method was false, the exception is ' - 'reraised.\n' - ' If the return value was true, the exception is suppressed, and\n' - ' execution continues with the statement following the "with"\n' - ' statement.\n' - '\n' - ' If the suite was exited for any reason other than an exception, ' - 'the\n' - ' return value from "__exit__()" is ignored, and execution ' - 'proceeds\n' - ' at the normal location for the kind of exit that was taken.\n' - '\n' - 'The following code:\n' - '\n' - ' with EXPRESSION as TARGET:\n' - ' SUITE\n' - '\n' - 'is semantically equivalent to:\n' - '\n' - ' manager = (EXPRESSION)\n' - ' enter = type(manager).__enter__\n' - ' exit = type(manager).__exit__\n' - ' value = enter(manager)\n' - ' hit_except = False\n' - '\n' - ' try:\n' - ' TARGET = value\n' - ' SUITE\n' - ' except:\n' - ' hit_except = True\n' - ' if not exit(manager, *sys.exc_info()):\n' - ' raise\n' - ' finally:\n' - ' if not hit_except:\n' - ' exit(manager, None, None, None)\n' - '\n' - 'With more than one item, the context managers are processed as if\n' - 'multiple "with" statements were nested:\n' - '\n' - ' with A() as a, B() as b:\n' - ' SUITE\n' - '\n' - 'is semantically equivalent to:\n' - '\n' - ' with A() as a:\n' - ' with B() as b:\n' - ' SUITE\n' - '\n' - 'You can also write multi-item context managers in multiple lines if\n' - 'the items are surrounded by parentheses. For example:\n' - '\n' - ' with (\n' - ' A() as a,\n' - ' B() as b,\n' - ' ):\n' - ' SUITE\n' - '\n' - 'Changed in version 3.1: Support for multiple context expressions.\n' - '\n' - 'Changed in version 3.10: Support for using grouping parentheses to\n' - 'break the statement in multiple lines.\n' - '\n' - 'See also:\n' - '\n' - ' **PEP 343** - The “with” statement\n' - ' The specification, background, and examples for the Python ' - '"with"\n' - ' statement.\n', - 'yield': 'The "yield" statement\n' - '*********************\n' - '\n' - ' yield_stmt ::= yield_expression\n' - '\n' - 'A "yield" statement is semantically equivalent to a yield ' - 'expression.\n' - 'The "yield" statement can be used to omit the parentheses that ' - 'would\n' - 'otherwise be required in the equivalent yield expression ' - 'statement.\n' - 'For example, the yield statements\n' - '\n' - ' yield <expr>\n' - ' yield from <expr>\n' - '\n' - 'are equivalent to the yield expression statements\n' - '\n' - ' (yield <expr>)\n' - ' (yield from <expr>)\n' - '\n' - 'Yield expressions and statements are only used when defining a\n' - '*generator* function, and are only used in the body of the ' - 'generator\n' - 'function. Using "yield" in a function definition is sufficient to\n' - 'cause that definition to create a generator function instead of a\n' - 'normal function.\n' - '\n' - 'For full details of "yield" semantics, refer to the Yield ' - 'expressions\n' - 'section.\n'} + +topics = { + 'assert': r'''The "assert" statement +********************** + +Assert statements are a convenient way to insert debugging assertions +into a program: + + assert_stmt ::= "assert" expression ["," expression] + +The simple form, "assert expression", is equivalent to + + if __debug__: + if not expression: raise AssertionError + +The extended form, "assert expression1, expression2", is equivalent to + + if __debug__: + if not expression1: raise AssertionError(expression2) + +These equivalences assume that "__debug__" and "AssertionError" refer +to the built-in variables with those names. In the current +implementation, the built-in variable "__debug__" is "True" under +normal circumstances, "False" when optimization is requested (command +line option "-O"). The current code generator emits no code for an +"assert" statement when optimization is requested at compile time. +Note that it is unnecessary to include the source code for the +expression that failed in the error message; it will be displayed as +part of the stack trace. + +Assignments to "__debug__" are illegal. The value for the built-in +variable is determined when the interpreter starts. +''', + 'assignment': r'''Assignment statements +********************* + +Assignment statements are used to (re)bind names to values and to +modify attributes or items of mutable objects: + + assignment_stmt ::= (target_list "=")+ (starred_expression | yield_expression) + target_list ::= target ("," target)* [","] + target ::= identifier + | "(" [target_list] ")" + | "[" [target_list] "]" + | attributeref + | subscription + | slicing + | "*" target + +(See section Primaries for the syntax definitions for *attributeref*, +*subscription*, and *slicing*.) + +An assignment statement evaluates the expression list (remember that +this can be a single expression or a comma-separated list, the latter +yielding a tuple) and assigns the single resulting object to each of +the target lists, from left to right. + +Assignment is defined recursively depending on the form of the target +(list). When a target is part of a mutable object (an attribute +reference, subscription or slicing), the mutable object must +ultimately perform the assignment and decide about its validity, and +may raise an exception if the assignment is unacceptable. The rules +observed by various types and the exceptions raised are given with the +definition of the object types (see section The standard type +hierarchy). + +Assignment of an object to a target list, optionally enclosed in +parentheses or square brackets, is recursively defined as follows. + +* If the target list is a single target with no trailing comma, + optionally in parentheses, the object is assigned to that target. + +* Else: + + * If the target list contains one target prefixed with an asterisk, + called a “starred” target: The object must be an iterable with at + least as many items as there are targets in the target list, minus + one. The first items of the iterable are assigned, from left to + right, to the targets before the starred target. The final items + of the iterable are assigned to the targets after the starred + target. A list of the remaining items in the iterable is then + assigned to the starred target (the list can be empty). + + * Else: The object must be an iterable with the same number of items + as there are targets in the target list, and the items are + assigned, from left to right, to the corresponding targets. + +Assignment of an object to a single target is recursively defined as +follows. + +* If the target is an identifier (name): + + * If the name does not occur in a "global" or "nonlocal" statement + in the current code block: the name is bound to the object in the + current local namespace. + + * Otherwise: the name is bound to the object in the global namespace + or the outer namespace determined by "nonlocal", respectively. + + The name is rebound if it was already bound. This may cause the + reference count for the object previously bound to the name to reach + zero, causing the object to be deallocated and its destructor (if it + has one) to be called. + +* If the target is an attribute reference: The primary expression in + the reference is evaluated. It should yield an object with + assignable attributes; if this is not the case, "TypeError" is + raised. That object is then asked to assign the assigned object to + the given attribute; if it cannot perform the assignment, it raises + an exception (usually but not necessarily "AttributeError"). + + Note: If the object is a class instance and the attribute reference + occurs on both sides of the assignment operator, the right-hand side + expression, "a.x" can access either an instance attribute or (if no + instance attribute exists) a class attribute. The left-hand side + target "a.x" is always set as an instance attribute, creating it if + necessary. Thus, the two occurrences of "a.x" do not necessarily + refer to the same attribute: if the right-hand side expression + refers to a class attribute, the left-hand side creates a new + instance attribute as the target of the assignment: + + class Cls: + x = 3 # class variable + inst = Cls() + inst.x = inst.x + 1 # writes inst.x as 4 leaving Cls.x as 3 + + This description does not necessarily apply to descriptor + attributes, such as properties created with "property()". + +* If the target is a subscription: The primary expression in the + reference is evaluated. It should yield either a mutable sequence + object (such as a list) or a mapping object (such as a dictionary). + Next, the subscript expression is evaluated. + + If the primary is a mutable sequence object (such as a list), the + subscript must yield an integer. If it is negative, the sequence’s + length is added to it. The resulting value must be a nonnegative + integer less than the sequence’s length, and the sequence is asked + to assign the assigned object to its item with that index. If the + index is out of range, "IndexError" is raised (assignment to a + subscripted sequence cannot add new items to a list). + + If the primary is a mapping object (such as a dictionary), the + subscript must have a type compatible with the mapping’s key type, + and the mapping is then asked to create a key/value pair which maps + the subscript to the assigned object. This can either replace an + existing key/value pair with the same key value, or insert a new + key/value pair (if no key with the same value existed). + + For user-defined objects, the "__setitem__()" method is called with + appropriate arguments. + +* If the target is a slicing: The primary expression in the reference + is evaluated. It should yield a mutable sequence object (such as a + list). The assigned object should be a sequence object of the same + type. Next, the lower and upper bound expressions are evaluated, + insofar they are present; defaults are zero and the sequence’s + length. The bounds should evaluate to integers. If either bound is + negative, the sequence’s length is added to it. The resulting + bounds are clipped to lie between zero and the sequence’s length, + inclusive. Finally, the sequence object is asked to replace the + slice with the items of the assigned sequence. The length of the + slice may be different from the length of the assigned sequence, + thus changing the length of the target sequence, if the target + sequence allows it. + +**CPython implementation detail:** In the current implementation, the +syntax for targets is taken to be the same as for expressions, and +invalid syntax is rejected during the code generation phase, causing +less detailed error messages. + +Although the definition of assignment implies that overlaps between +the left-hand side and the right-hand side are ‘simultaneous’ (for +example "a, b = b, a" swaps two variables), overlaps *within* the +collection of assigned-to variables occur left-to-right, sometimes +resulting in confusion. For instance, the following program prints +"[0, 2]": + + x = [0, 1] + i = 0 + i, x[i] = 1, 2 # i is updated, then x[i] is updated + print(x) + +See also: + + **PEP 3132** - Extended Iterable Unpacking + The specification for the "*target" feature. + + +Augmented assignment statements +=============================== + +Augmented assignment is the combination, in a single statement, of a +binary operation and an assignment statement: + + augmented_assignment_stmt ::= augtarget augop (expression_list | yield_expression) + augtarget ::= identifier | attributeref | subscription | slicing + augop ::= "+=" | "-=" | "*=" | "@=" | "/=" | "//=" | "%=" | "**=" + | ">>=" | "<<=" | "&=" | "^=" | "|=" + +(See section Primaries for the syntax definitions of the last three +symbols.) + +An augmented assignment evaluates the target (which, unlike normal +assignment statements, cannot be an unpacking) and the expression +list, performs the binary operation specific to the type of assignment +on the two operands, and assigns the result to the original target. +The target is only evaluated once. + +An augmented assignment statement like "x += 1" can be rewritten as "x += x + 1" to achieve a similar, but not exactly equal effect. In the +augmented version, "x" is only evaluated once. Also, when possible, +the actual operation is performed *in-place*, meaning that rather than +creating a new object and assigning that to the target, the old object +is modified instead. + +Unlike normal assignments, augmented assignments evaluate the left- +hand side *before* evaluating the right-hand side. For example, "a[i] ++= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and performs +the addition, and lastly, it writes the result back to "a[i]". + +With the exception of assigning to tuples and multiple targets in a +single statement, the assignment done by augmented assignment +statements is handled the same way as normal assignments. Similarly, +with the exception of the possible *in-place* behavior, the binary +operation performed by augmented assignment is the same as the normal +binary operations. + +For targets which are attribute references, the same caveat about +class and instance attributes applies as for regular assignments. + + +Annotated assignment statements +=============================== + +*Annotation* assignment is the combination, in a single statement, of +a variable or attribute annotation and an optional assignment +statement: + + annotated_assignment_stmt ::= augtarget ":" expression + ["=" (starred_expression | yield_expression)] + +The difference from normal Assignment statements is that only a single +target is allowed. + +The assignment target is considered “simple” if it consists of a +single name that is not enclosed in parentheses. For simple assignment +targets, if in class or module scope, the annotations are gathered in +a lazily evaluated annotation scope. The annotations can be evaluated +using the "__annotations__" attribute of a class or module, or using +the facilities in the "annotationlib" module. + +If the assignment target is not simple (an attribute, subscript node, +or parenthesized name), the annotation is never evaluated. + +If a name is annotated in a function scope, then this name is local +for that scope. Annotations are never evaluated and stored in function +scopes. + +If the right hand side is present, an annotated assignment performs +the actual assignment as if there was no annotation present. If the +right hand side is not present for an expression target, then the +interpreter evaluates the target except for the last "__setitem__()" +or "__setattr__()" call. + +See also: + + **PEP 526** - Syntax for Variable Annotations + The proposal that added syntax for annotating the types of + variables (including class variables and instance variables), + instead of expressing them through comments. + + **PEP 484** - Type hints + The proposal that added the "typing" module to provide a standard + syntax for type annotations that can be used in static analysis + tools and IDEs. + +Changed in version 3.8: Now annotated assignments allow the same +expressions in the right hand side as regular assignments. Previously, +some expressions (like un-parenthesized tuple expressions) caused a +syntax error. + +Changed in version 3.14: Annotations are now lazily evaluated in a +separate annotation scope. If the assignment target is not simple, +annotations are never evaluated. +''', + 'assignment-expressions': r'''Assignment expressions +********************** + + assignment_expression ::= [identifier ":="] expression + +An assignment expression (sometimes also called a “named expression” +or “walrus”) assigns an "expression" to an "identifier", while also +returning the value of the "expression". + +One common use case is when handling matched regular expressions: + + if matching := pattern.search(data): + do_something(matching) + +Or, when processing a file stream in chunks: + + while chunk := file.read(9000): + process(chunk) + +Assignment expressions must be surrounded by parentheses when used as +expression statements and when used as sub-expressions in slicing, +conditional, lambda, keyword-argument, and comprehension-if +expressions and in "assert", "with", and "assignment" statements. In +all other places where they can be used, parentheses are not required, +including in "if" and "while" statements. + +Added in version 3.8: See **PEP 572** for more details about +assignment expressions. +''', + 'async': r'''Coroutines +********** + +Added in version 3.5. + + +Coroutine function definition +============================= + + async_funcdef ::= [decorators] "async" "def" funcname "(" [parameter_list] ")" + ["->" expression] ":" suite + +Execution of Python coroutines can be suspended and resumed at many +points (see *coroutine*). "await" expressions, "async for" and "async +with" can only be used in the body of a coroutine function. + +Functions defined with "async def" syntax are always coroutine +functions, even if they do not contain "await" or "async" keywords. + +It is a "SyntaxError" to use a "yield from" expression inside the body +of a coroutine function. + +An example of a coroutine function: + + async def func(param1, param2): + do_stuff() + await some_coroutine() + +Changed in version 3.7: "await" and "async" are now keywords; +previously they were only treated as such inside the body of a +coroutine function. + + +The "async for" statement +========================= + + async_for_stmt ::= "async" for_stmt + +An *asynchronous iterable* provides an "__aiter__" method that +directly returns an *asynchronous iterator*, which can call +asynchronous code in its "__anext__" method. + +The "async for" statement allows convenient iteration over +asynchronous iterables. + +The following code: + + async for TARGET in ITER: + SUITE + else: + SUITE2 + +Is semantically equivalent to: + + iter = (ITER) + iter = type(iter).__aiter__(iter) + running = True + + while running: + try: + TARGET = await type(iter).__anext__(iter) + except StopAsyncIteration: + running = False + else: + SUITE + else: + SUITE2 + +See also "__aiter__()" and "__anext__()" for details. + +It is a "SyntaxError" to use an "async for" statement outside the body +of a coroutine function. + + +The "async with" statement +========================== + + async_with_stmt ::= "async" with_stmt + +An *asynchronous context manager* is a *context manager* that is able +to suspend execution in its *enter* and *exit* methods. + +The following code: + + async with EXPRESSION as TARGET: + SUITE + +is semantically equivalent to: + + manager = (EXPRESSION) + aenter = type(manager).__aenter__ + aexit = type(manager).__aexit__ + value = await aenter(manager) + hit_except = False + + try: + TARGET = value + SUITE + except: + hit_except = True + if not await aexit(manager, *sys.exc_info()): + raise + finally: + if not hit_except: + await aexit(manager, None, None, None) + +See also "__aenter__()" and "__aexit__()" for details. + +It is a "SyntaxError" to use an "async with" statement outside the +body of a coroutine function. + +See also: + + **PEP 492** - Coroutines with async and await syntax + The proposal that made coroutines a proper standalone concept in + Python, and added supporting syntax. +''', + 'atom-identifiers': r'''Identifiers (Names) +******************* + +An identifier occurring as an atom is a name. See section Identifiers +and keywords for lexical definition and section Naming and binding for +documentation of naming and binding. + +When the name is bound to an object, evaluation of the atom yields +that object. When a name is not bound, an attempt to evaluate it +raises a "NameError" exception. + + +Private name mangling +===================== + +When an identifier that textually occurs in a class definition begins +with two or more underscore characters and does not end in two or more +underscores, it is considered a *private name* of that class. + +See also: The class specifications. + +More precisely, private names are transformed to a longer form before +code is generated for them. If the transformed name is longer than +255 characters, implementation-defined truncation may happen. + +The transformation is independent of the syntactical context in which +the identifier is used but only the following private identifiers are +mangled: + +* Any name used as the name of a variable that is assigned or read or + any name of an attribute being accessed. + + The "__name__" attribute of nested functions, classes, and type + aliases is however not mangled. + +* The name of imported modules, e.g., "__spam" in "import __spam". If + the module is part of a package (i.e., its name contains a dot), the + name is *not* mangled, e.g., the "__foo" in "import __foo.bar" is + not mangled. + +* The name of an imported member, e.g., "__f" in "from spam import + __f". + +The transformation rule is defined as follows: + +* The class name, with leading underscores removed and a single + leading underscore inserted, is inserted in front of the identifier, + e.g., the identifier "__spam" occurring in a class named "Foo", + "_Foo" or "__Foo" is transformed to "_Foo__spam". + +* If the class name consists only of underscores, the transformation + is the identity, e.g., the identifier "__spam" occurring in a class + named "_" or "__" is left as is. +''', + 'atom-literals': r'''Literals +******** + +Python supports string and bytes literals and various numeric +literals: + + literal ::= stringliteral | bytesliteral + | integer | floatnumber | imagnumber + +Evaluation of a literal yields an object of the given type (string, +bytes, integer, floating-point number, complex number) with the given +value. The value may be approximated in the case of floating-point +and imaginary (complex) literals. See section Literals for details. + +All literals correspond to immutable data types, and hence the +object’s identity is less important than its value. Multiple +evaluations of literals with the same value (either the same +occurrence in the program text or a different occurrence) may obtain +the same object or a different object with the same value. +''', + 'attribute-access': r'''Customizing attribute access +**************************** + +The following methods can be defined to customize the meaning of +attribute access (use of, assignment to, or deletion of "x.name") for +class instances. + +object.__getattr__(self, name) + + Called when the default attribute access fails with an + "AttributeError" (either "__getattribute__()" raises an + "AttributeError" because *name* is not an instance attribute or an + attribute in the class tree for "self"; or "__get__()" of a *name* + property raises "AttributeError"). This method should either + return the (computed) attribute value or raise an "AttributeError" + exception. The "object" class itself does not provide this method. + + Note that if the attribute is found through the normal mechanism, + "__getattr__()" is not called. (This is an intentional asymmetry + between "__getattr__()" and "__setattr__()".) This is done both for + efficiency reasons and because otherwise "__getattr__()" would have + no way to access other attributes of the instance. Note that at + least for instance variables, you can take total control by not + inserting any values in the instance attribute dictionary (but + instead inserting them in another object). See the + "__getattribute__()" method below for a way to actually get total + control over attribute access. + +object.__getattribute__(self, name) + + Called unconditionally to implement attribute accesses for + instances of the class. If the class also defines "__getattr__()", + the latter will not be called unless "__getattribute__()" either + calls it explicitly or raises an "AttributeError". This method + should return the (computed) attribute value or raise an + "AttributeError" exception. In order to avoid infinite recursion in + this method, its implementation should always call the base class + method with the same name to access any attributes it needs, for + example, "object.__getattribute__(self, name)". + + Note: + + This method may still be bypassed when looking up special methods + as the result of implicit invocation via language syntax or + built-in functions. See Special method lookup. + + For certain sensitive attribute accesses, raises an auditing event + "object.__getattr__" with arguments "obj" and "name". + +object.__setattr__(self, name, value) + + Called when an attribute assignment is attempted. This is called + instead of the normal mechanism (i.e. store the value in the + instance dictionary). *name* is the attribute name, *value* is the + value to be assigned to it. + + If "__setattr__()" wants to assign to an instance attribute, it + should call the base class method with the same name, for example, + "object.__setattr__(self, name, value)". + + For certain sensitive attribute assignments, raises an auditing + event "object.__setattr__" with arguments "obj", "name", "value". + +object.__delattr__(self, name) + + Like "__setattr__()" but for attribute deletion instead of + assignment. This should only be implemented if "del obj.name" is + meaningful for the object. + + For certain sensitive attribute deletions, raises an auditing event + "object.__delattr__" with arguments "obj" and "name". + +object.__dir__(self) + + Called when "dir()" is called on the object. An iterable must be + returned. "dir()" converts the returned iterable to a list and + sorts it. + + +Customizing module attribute access +=================================== + +Special names "__getattr__" and "__dir__" can be also used to +customize access to module attributes. The "__getattr__" function at +the module level should accept one argument which is the name of an +attribute and return the computed value or raise an "AttributeError". +If an attribute is not found on a module object through the normal +lookup, i.e. "object.__getattribute__()", then "__getattr__" is +searched in the module "__dict__" before raising an "AttributeError". +If found, it is called with the attribute name and the result is +returned. + +The "__dir__" function should accept no arguments, and return an +iterable of strings that represents the names accessible on module. If +present, this function overrides the standard "dir()" search on a +module. + +For a more fine grained customization of the module behavior (setting +attributes, properties, etc.), one can set the "__class__" attribute +of a module object to a subclass of "types.ModuleType". For example: + + import sys + from types import ModuleType + + class VerboseModule(ModuleType): + def __repr__(self): + return f'Verbose {self.__name__}' + + def __setattr__(self, attr, value): + print(f'Setting {attr}...') + super().__setattr__(attr, value) + + sys.modules[__name__].__class__ = VerboseModule + +Note: + + Defining module "__getattr__" and setting module "__class__" only + affect lookups made using the attribute access syntax – directly + accessing the module globals (whether by code within the module, or + via a reference to the module’s globals dictionary) is unaffected. + +Changed in version 3.5: "__class__" module attribute is now writable. + +Added in version 3.7: "__getattr__" and "__dir__" module attributes. + +See also: + + **PEP 562** - Module __getattr__ and __dir__ + Describes the "__getattr__" and "__dir__" functions on modules. + + +Implementing Descriptors +======================== + +The following methods only apply when an instance of the class +containing the method (a so-called *descriptor* class) appears in an +*owner* class (the descriptor must be in either the owner’s class +dictionary or in the class dictionary for one of its parents). In the +examples below, “the attribute” refers to the attribute whose name is +the key of the property in the owner class’ "__dict__". The "object" +class itself does not implement any of these protocols. + +object.__get__(self, instance, owner=None) + + Called to get the attribute of the owner class (class attribute + access) or of an instance of that class (instance attribute + access). The optional *owner* argument is the owner class, while + *instance* is the instance that the attribute was accessed through, + or "None" when the attribute is accessed through the *owner*. + + This method should return the computed attribute value or raise an + "AttributeError" exception. + + **PEP 252** specifies that "__get__()" is callable with one or two + arguments. Python’s own built-in descriptors support this + specification; however, it is likely that some third-party tools + have descriptors that require both arguments. Python’s own + "__getattribute__()" implementation always passes in both arguments + whether they are required or not. + +object.__set__(self, instance, value) + + Called to set the attribute on an instance *instance* of the owner + class to a new value, *value*. + + Note, adding "__set__()" or "__delete__()" changes the kind of + descriptor to a “data descriptor”. See Invoking Descriptors for + more details. + +object.__delete__(self, instance) + + Called to delete the attribute on an instance *instance* of the + owner class. + +Instances of descriptors may also have the "__objclass__" attribute +present: + +object.__objclass__ + + The attribute "__objclass__" is interpreted by the "inspect" module + as specifying the class where this object was defined (setting this + appropriately can assist in runtime introspection of dynamic class + attributes). For callables, it may indicate that an instance of the + given type (or a subclass) is expected or required as the first + positional argument (for example, CPython sets this attribute for + unbound methods that are implemented in C). + + +Invoking Descriptors +==================== + +In general, a descriptor is an object attribute with “binding +behavior”, one whose attribute access has been overridden by methods +in the descriptor protocol: "__get__()", "__set__()", and +"__delete__()". If any of those methods are defined for an object, it +is said to be a descriptor. + +The default behavior for attribute access is to get, set, or delete +the attribute from an object’s dictionary. For instance, "a.x" has a +lookup chain starting with "a.__dict__['x']", then +"type(a).__dict__['x']", and continuing through the base classes of +"type(a)" excluding metaclasses. + +However, if the looked-up value is an object defining one of the +descriptor methods, then Python may override the default behavior and +invoke the descriptor method instead. Where this occurs in the +precedence chain depends on which descriptor methods were defined and +how they were called. + +The starting point for descriptor invocation is a binding, "a.x". How +the arguments are assembled depends on "a": + +Direct Call + The simplest and least common call is when user code directly + invokes a descriptor method: "x.__get__(a)". + +Instance Binding + If binding to an object instance, "a.x" is transformed into the + call: "type(a).__dict__['x'].__get__(a, type(a))". + +Class Binding + If binding to a class, "A.x" is transformed into the call: + "A.__dict__['x'].__get__(None, A)". + +Super Binding + A dotted lookup such as "super(A, a).x" searches + "a.__class__.__mro__" for a base class "B" following "A" and then + returns "B.__dict__['x'].__get__(a, A)". If not a descriptor, "x" + is returned unchanged. + +For instance bindings, the precedence of descriptor invocation depends +on which descriptor methods are defined. A descriptor can define any +combination of "__get__()", "__set__()" and "__delete__()". If it +does not define "__get__()", then accessing the attribute will return +the descriptor object itself unless there is a value in the object’s +instance dictionary. If the descriptor defines "__set__()" and/or +"__delete__()", it is a data descriptor; if it defines neither, it is +a non-data descriptor. Normally, data descriptors define both +"__get__()" and "__set__()", while non-data descriptors have just the +"__get__()" method. Data descriptors with "__get__()" and "__set__()" +(and/or "__delete__()") defined always override a redefinition in an +instance dictionary. In contrast, non-data descriptors can be +overridden by instances. + +Python methods (including those decorated with "@staticmethod" and +"@classmethod") are implemented as non-data descriptors. Accordingly, +instances can redefine and override methods. This allows individual +instances to acquire behaviors that differ from other instances of the +same class. + +The "property()" function is implemented as a data descriptor. +Accordingly, instances cannot override the behavior of a property. + + +__slots__ +========= + +*__slots__* allow us to explicitly declare data members (like +properties) and deny the creation of "__dict__" and *__weakref__* +(unless explicitly declared in *__slots__* or available in a parent.) + +The space saved over using "__dict__" can be significant. Attribute +lookup speed can be significantly improved as well. + +object.__slots__ + + This class variable can be assigned a string, iterable, or sequence + of strings with variable names used by instances. *__slots__* + reserves space for the declared variables and prevents the + automatic creation of "__dict__" and *__weakref__* for each + instance. + +Notes on using *__slots__*: + +* When inheriting from a class without *__slots__*, the "__dict__" and + *__weakref__* attribute of the instances will always be accessible. + +* Without a "__dict__" variable, instances cannot be assigned new + variables not listed in the *__slots__* definition. Attempts to + assign to an unlisted variable name raises "AttributeError". If + dynamic assignment of new variables is desired, then add + "'__dict__'" to the sequence of strings in the *__slots__* + declaration. + +* Without a *__weakref__* variable for each instance, classes defining + *__slots__* do not support "weak references" to its instances. If + weak reference support is needed, then add "'__weakref__'" to the + sequence of strings in the *__slots__* declaration. + +* *__slots__* are implemented at the class level by creating + descriptors for each variable name. As a result, class attributes + cannot be used to set default values for instance variables defined + by *__slots__*; otherwise, the class attribute would overwrite the + descriptor assignment. + +* The action of a *__slots__* declaration is not limited to the class + where it is defined. *__slots__* declared in parents are available + in child classes. However, instances of a child subclass will get a + "__dict__" and *__weakref__* unless the subclass also defines + *__slots__* (which should only contain names of any *additional* + slots). + +* If a class defines a slot also defined in a base class, the instance + variable defined by the base class slot is inaccessible (except by + retrieving its descriptor directly from the base class). This + renders the meaning of the program undefined. In the future, a + check may be added to prevent this. + +* "TypeError" will be raised if nonempty *__slots__* are defined for a + class derived from a ""variable-length" built-in type" such as + "int", "bytes", and "tuple". + +* Any non-string *iterable* may be assigned to *__slots__*. + +* If a "dictionary" is used to assign *__slots__*, the dictionary keys + will be used as the slot names. The values of the dictionary can be + used to provide per-attribute docstrings that will be recognised by + "inspect.getdoc()" and displayed in the output of "help()". + +* "__class__" assignment works only if both classes have the same + *__slots__*. + +* Multiple inheritance with multiple slotted parent classes can be + used, but only one parent is allowed to have attributes created by + slots (the other bases must have empty slot layouts) - violations + raise "TypeError". + +* If an *iterator* is used for *__slots__* then a *descriptor* is + created for each of the iterator’s values. However, the *__slots__* + attribute will be an empty iterator. +''', + 'attribute-references': r'''Attribute references +******************** + +An attribute reference is a primary followed by a period and a name: + + attributeref ::= primary "." identifier + +The primary must evaluate to an object of a type that supports +attribute references, which most objects do. This object is then +asked to produce the attribute whose name is the identifier. The type +and value produced is determined by the object. Multiple evaluations +of the same attribute reference may yield different objects. + +This production can be customized by overriding the +"__getattribute__()" method or the "__getattr__()" method. The +"__getattribute__()" method is called first and either returns a value +or raises "AttributeError" if the attribute is not available. + +If an "AttributeError" is raised and the object has a "__getattr__()" +method, that method is called as a fallback. +''', + 'augassign': r'''Augmented assignment statements +******************************* + +Augmented assignment is the combination, in a single statement, of a +binary operation and an assignment statement: + + augmented_assignment_stmt ::= augtarget augop (expression_list | yield_expression) + augtarget ::= identifier | attributeref | subscription | slicing + augop ::= "+=" | "-=" | "*=" | "@=" | "/=" | "//=" | "%=" | "**=" + | ">>=" | "<<=" | "&=" | "^=" | "|=" + +(See section Primaries for the syntax definitions of the last three +symbols.) + +An augmented assignment evaluates the target (which, unlike normal +assignment statements, cannot be an unpacking) and the expression +list, performs the binary operation specific to the type of assignment +on the two operands, and assigns the result to the original target. +The target is only evaluated once. + +An augmented assignment statement like "x += 1" can be rewritten as "x += x + 1" to achieve a similar, but not exactly equal effect. In the +augmented version, "x" is only evaluated once. Also, when possible, +the actual operation is performed *in-place*, meaning that rather than +creating a new object and assigning that to the target, the old object +is modified instead. + +Unlike normal assignments, augmented assignments evaluate the left- +hand side *before* evaluating the right-hand side. For example, "a[i] ++= f(x)" first looks-up "a[i]", then it evaluates "f(x)" and performs +the addition, and lastly, it writes the result back to "a[i]". + +With the exception of assigning to tuples and multiple targets in a +single statement, the assignment done by augmented assignment +statements is handled the same way as normal assignments. Similarly, +with the exception of the possible *in-place* behavior, the binary +operation performed by augmented assignment is the same as the normal +binary operations. + +For targets which are attribute references, the same caveat about +class and instance attributes applies as for regular assignments. +''', + 'await': r'''Await expression +**************** + +Suspend the execution of *coroutine* on an *awaitable* object. Can +only be used inside a *coroutine function*. + + await_expr ::= "await" primary + +Added in version 3.5. +''', + 'binary': r'''Binary arithmetic operations +**************************** + +The binary arithmetic operations have the conventional priority +levels. Note that some of these operations also apply to certain non- +numeric types. Apart from the power operator, there are only two +levels, one for multiplicative operators and one for additive +operators: + + m_expr ::= u_expr | m_expr "*" u_expr | m_expr "@" m_expr | + m_expr "//" u_expr | m_expr "/" u_expr | + m_expr "%" u_expr + a_expr ::= m_expr | a_expr "+" m_expr | a_expr "-" m_expr + +The "*" (multiplication) operator yields the product of its arguments. +The arguments must either both be numbers, or one argument must be an +integer and the other must be a sequence. In the former case, the +numbers are converted to a common real type and then multiplied +together. In the latter case, sequence repetition is performed; a +negative repetition factor yields an empty sequence. + +This operation can be customized using the special "__mul__()" and +"__rmul__()" methods. + +Changed in version 3.14: If only one operand is a complex number, the +other operand is converted to a floating-point number. + +The "@" (at) operator is intended to be used for matrix +multiplication. No builtin Python types implement this operator. + +This operation can be customized using the special "__matmul__()" and +"__rmatmul__()" methods. + +Added in version 3.5. + +The "/" (division) and "//" (floor division) operators yield the +quotient of their arguments. The numeric arguments are first +converted to a common type. Division of integers yields a float, while +floor division of integers results in an integer; the result is that +of mathematical division with the ‘floor’ function applied to the +result. Division by zero raises the "ZeroDivisionError" exception. + +The division operation can be customized using the special +"__truediv__()" and "__rtruediv__()" methods. The floor division +operation can be customized using the special "__floordiv__()" and +"__rfloordiv__()" methods. + +The "%" (modulo) operator yields the remainder from the division of +the first argument by the second. The numeric arguments are first +converted to a common type. A zero right argument raises the +"ZeroDivisionError" exception. The arguments may be floating-point +numbers, e.g., "3.14%0.7" equals "0.34" (since "3.14" equals "4*0.7 + +0.34".) The modulo operator always yields a result with the same sign +as its second operand (or zero); the absolute value of the result is +strictly smaller than the absolute value of the second operand [1]. + +The floor division and modulo operators are connected by the following +identity: "x == (x//y)*y + (x%y)". Floor division and modulo are also +connected with the built-in function "divmod()": "divmod(x, y) == +(x//y, x%y)". [2]. + +In addition to performing the modulo operation on numbers, the "%" +operator is also overloaded by string objects to perform old-style +string formatting (also known as interpolation). The syntax for +string formatting is described in the Python Library Reference, +section printf-style String Formatting. + +The *modulo* operation can be customized using the special "__mod__()" +and "__rmod__()" methods. + +The floor division operator, the modulo operator, and the "divmod()" +function are not defined for complex numbers. Instead, convert to a +floating-point number using the "abs()" function if appropriate. + +The "+" (addition) operator yields the sum of its arguments. The +arguments must either both be numbers or both be sequences of the same +type. In the former case, the numbers are converted to a common real +type and then added together. In the latter case, the sequences are +concatenated. + +This operation can be customized using the special "__add__()" and +"__radd__()" methods. + +Changed in version 3.14: If only one operand is a complex number, the +other operand is converted to a floating-point number. + +The "-" (subtraction) operator yields the difference of its arguments. +The numeric arguments are first converted to a common real type. + +This operation can be customized using the special "__sub__()" and +"__rsub__()" methods. + +Changed in version 3.14: If only one operand is a complex number, the +other operand is converted to a floating-point number. +''', + 'bitwise': r'''Binary bitwise operations +************************* + +Each of the three bitwise operations has a different priority level: + + and_expr ::= shift_expr | and_expr "&" shift_expr + xor_expr ::= and_expr | xor_expr "^" and_expr + or_expr ::= xor_expr | or_expr "|" xor_expr + +The "&" operator yields the bitwise AND of its arguments, which must +be integers or one of them must be a custom object overriding +"__and__()" or "__rand__()" special methods. + +The "^" operator yields the bitwise XOR (exclusive OR) of its +arguments, which must be integers or one of them must be a custom +object overriding "__xor__()" or "__rxor__()" special methods. + +The "|" operator yields the bitwise (inclusive) OR of its arguments, +which must be integers or one of them must be a custom object +overriding "__or__()" or "__ror__()" special methods. +''', + 'bltin-code-objects': r'''Code Objects +************ + +Code objects are used by the implementation to represent “pseudo- +compiled” executable Python code such as a function body. They differ +from function objects because they don’t contain a reference to their +global execution environment. Code objects are returned by the built- +in "compile()" function and can be extracted from function objects +through their "__code__" attribute. See also the "code" module. + +Accessing "__code__" raises an auditing event "object.__getattr__" +with arguments "obj" and ""__code__"". + +A code object can be executed or evaluated by passing it (instead of a +source string) to the "exec()" or "eval()" built-in functions. + +See The standard type hierarchy for more information. +''', + 'bltin-ellipsis-object': r'''The Ellipsis Object +******************* + +This object is commonly used by slicing (see Slicings). It supports +no special operations. There is exactly one ellipsis object, named +"Ellipsis" (a built-in name). "type(Ellipsis)()" produces the +"Ellipsis" singleton. + +It is written as "Ellipsis" or "...". +''', + 'bltin-null-object': r'''The Null Object +*************** + +This object is returned by functions that don’t explicitly return a +value. It supports no special operations. There is exactly one null +object, named "None" (a built-in name). "type(None)()" produces the +same singleton. + +It is written as "None". +''', + 'bltin-type-objects': r'''Type Objects +************ + +Type objects represent the various object types. An object’s type is +accessed by the built-in function "type()". There are no special +operations on types. The standard module "types" defines names for +all standard built-in types. + +Types are written like this: "<class 'int'>". +''', + 'booleans': r'''Boolean operations +****************** + + or_test ::= and_test | or_test "or" and_test + and_test ::= not_test | and_test "and" not_test + not_test ::= comparison | "not" not_test + +In the context of Boolean operations, and also when expressions are +used by control flow statements, the following values are interpreted +as false: "False", "None", numeric zero of all types, and empty +strings and containers (including strings, tuples, lists, +dictionaries, sets and frozensets). All other values are interpreted +as true. User-defined objects can customize their truth value by +providing a "__bool__()" method. + +The operator "not" yields "True" if its argument is false, "False" +otherwise. + +The expression "x and y" first evaluates *x*; if *x* is false, its +value is returned; otherwise, *y* is evaluated and the resulting value +is returned. + +The expression "x or y" first evaluates *x*; if *x* is true, its value +is returned; otherwise, *y* is evaluated and the resulting value is +returned. + +Note that neither "and" nor "or" restrict the value and type they +return to "False" and "True", but rather return the last evaluated +argument. This is sometimes useful, e.g., if "s" is a string that +should be replaced by a default value if it is empty, the expression +"s or 'foo'" yields the desired value. Because "not" has to create a +new value, it returns a boolean value regardless of the type of its +argument (for example, "not 'foo'" produces "False" rather than "''".) +''', + 'break': r'''The "break" statement +********************* + + break_stmt ::= "break" + +"break" may only occur syntactically nested in a "for" or "while" +loop, but not nested in a function or class definition within that +loop. + +It terminates the nearest enclosing loop, skipping the optional "else" +clause if the loop has one. + +If a "for" loop is terminated by "break", the loop control target +keeps its current value. + +When "break" passes control out of a "try" statement with a "finally" +clause, that "finally" clause is executed before really leaving the +loop. +''', + 'callable-types': r'''Emulating callable objects +************************** + +object.__call__(self[, args...]) + + Called when the instance is “called” as a function; if this method + is defined, "x(arg1, arg2, ...)" roughly translates to + "type(x).__call__(x, arg1, ...)". The "object" class itself does + not provide this method. +''', + 'calls': r'''Calls +***** + +A call calls a callable object (e.g., a *function*) with a possibly +empty series of *arguments*: + + call ::= primary "(" [argument_list [","] | comprehension] ")" + argument_list ::= positional_arguments ["," starred_and_keywords] + ["," keywords_arguments] + | starred_and_keywords ["," keywords_arguments] + | keywords_arguments + positional_arguments ::= positional_item ("," positional_item)* + positional_item ::= assignment_expression | "*" expression + starred_and_keywords ::= ("*" expression | keyword_item) + ("," "*" expression | "," keyword_item)* + keywords_arguments ::= (keyword_item | "**" expression) + ("," keyword_item | "," "**" expression)* + keyword_item ::= identifier "=" expression + +An optional trailing comma may be present after the positional and +keyword arguments but does not affect the semantics. + +The primary must evaluate to a callable object (user-defined +functions, built-in functions, methods of built-in objects, class +objects, methods of class instances, and all objects having a +"__call__()" method are callable). All argument expressions are +evaluated before the call is attempted. Please refer to section +Function definitions for the syntax of formal *parameter* lists. + +If keyword arguments are present, they are first converted to +positional arguments, as follows. First, a list of unfilled slots is +created for the formal parameters. If there are N positional +arguments, they are placed in the first N slots. Next, for each +keyword argument, the identifier is used to determine the +corresponding slot (if the identifier is the same as the first formal +parameter name, the first slot is used, and so on). If the slot is +already filled, a "TypeError" exception is raised. Otherwise, the +argument is placed in the slot, filling it (even if the expression is +"None", it fills the slot). When all arguments have been processed, +the slots that are still unfilled are filled with the corresponding +default value from the function definition. (Default values are +calculated, once, when the function is defined; thus, a mutable object +such as a list or dictionary used as default value will be shared by +all calls that don’t specify an argument value for the corresponding +slot; this should usually be avoided.) If there are any unfilled +slots for which no default value is specified, a "TypeError" exception +is raised. Otherwise, the list of filled slots is used as the +argument list for the call. + +**CPython implementation detail:** An implementation may provide +built-in functions whose positional parameters do not have names, even +if they are ‘named’ for the purpose of documentation, and which +therefore cannot be supplied by keyword. In CPython, this is the case +for functions implemented in C that use "PyArg_ParseTuple()" to parse +their arguments. + +If there are more positional arguments than there are formal parameter +slots, a "TypeError" exception is raised, unless a formal parameter +using the syntax "*identifier" is present; in this case, that formal +parameter receives a tuple containing the excess positional arguments +(or an empty tuple if there were no excess positional arguments). + +If any keyword argument does not correspond to a formal parameter +name, a "TypeError" exception is raised, unless a formal parameter +using the syntax "**identifier" is present; in this case, that formal +parameter receives a dictionary containing the excess keyword +arguments (using the keywords as keys and the argument values as +corresponding values), or a (new) empty dictionary if there were no +excess keyword arguments. + +If the syntax "*expression" appears in the function call, "expression" +must evaluate to an *iterable*. Elements from these iterables are +treated as if they were additional positional arguments. For the call +"f(x1, x2, *y, x3, x4)", if *y* evaluates to a sequence *y1*, …, *yM*, +this is equivalent to a call with M+4 positional arguments *x1*, *x2*, +*y1*, …, *yM*, *x3*, *x4*. + +A consequence of this is that although the "*expression" syntax may +appear *after* explicit keyword arguments, it is processed *before* +the keyword arguments (and any "**expression" arguments – see below). +So: + + >>> def f(a, b): + ... print(a, b) + ... + >>> f(b=1, *(2,)) + 2 1 + >>> f(a=1, *(2,)) + Traceback (most recent call last): + File "<stdin>", line 1, in <module> + TypeError: f() got multiple values for keyword argument 'a' + >>> f(1, *(2,)) + 1 2 + +It is unusual for both keyword arguments and the "*expression" syntax +to be used in the same call, so in practice this confusion does not +often arise. + +If the syntax "**expression" appears in the function call, +"expression" must evaluate to a *mapping*, the contents of which are +treated as additional keyword arguments. If a parameter matching a key +has already been given a value (by an explicit keyword argument, or +from another unpacking), a "TypeError" exception is raised. + +When "**expression" is used, each key in this mapping must be a +string. Each value from the mapping is assigned to the first formal +parameter eligible for keyword assignment whose name is equal to the +key. A key need not be a Python identifier (e.g. ""max-temp °F"" is +acceptable, although it will not match any formal parameter that could +be declared). If there is no match to a formal parameter the key-value +pair is collected by the "**" parameter, if there is one, or if there +is not, a "TypeError" exception is raised. + +Formal parameters using the syntax "*identifier" or "**identifier" +cannot be used as positional argument slots or as keyword argument +names. + +Changed in version 3.5: Function calls accept any number of "*" and +"**" unpackings, positional arguments may follow iterable unpackings +("*"), and keyword arguments may follow dictionary unpackings ("**"). +Originally proposed by **PEP 448**. + +A call always returns some value, possibly "None", unless it raises an +exception. How this value is computed depends on the type of the +callable object. + +If it is— + +a user-defined function: + The code block for the function is executed, passing it the + argument list. The first thing the code block will do is bind the + formal parameters to the arguments; this is described in section + Function definitions. When the code block executes a "return" + statement, this specifies the return value of the function call. + If execution reaches the end of the code block without executing a + "return" statement, the return value is "None". + +a built-in function or method: + The result is up to the interpreter; see Built-in Functions for the + descriptions of built-in functions and methods. + +a class object: + A new instance of that class is returned. + +a class instance method: + The corresponding user-defined function is called, with an argument + list that is one longer than the argument list of the call: the + instance becomes the first argument. + +a class instance: + The class must define a "__call__()" method; the effect is then the + same as if that method was called. +''', + 'class': r'''Class definitions +***************** + +A class definition defines a class object (see section The standard +type hierarchy): + + classdef ::= [decorators] "class" classname [type_params] [inheritance] ":" suite + inheritance ::= "(" [argument_list] ")" + classname ::= identifier + +A class definition is an executable statement. The inheritance list +usually gives a list of base classes (see Metaclasses for more +advanced uses), so each item in the list should evaluate to a class +object which allows subclassing. Classes without an inheritance list +inherit, by default, from the base class "object"; hence, + + class Foo: + pass + +is equivalent to + + class Foo(object): + pass + +The class’s suite is then executed in a new execution frame (see +Naming and binding), using a newly created local namespace and the +original global namespace. (Usually, the suite contains mostly +function definitions.) When the class’s suite finishes execution, its +execution frame is discarded but its local namespace is saved. [5] A +class object is then created using the inheritance list for the base +classes and the saved local namespace for the attribute dictionary. +The class name is bound to this class object in the original local +namespace. + +The order in which attributes are defined in the class body is +preserved in the new class’s "__dict__". Note that this is reliable +only right after the class is created and only for classes that were +defined using the definition syntax. + +Class creation can be customized heavily using metaclasses. + +Classes can also be decorated: just like when decorating functions, + + @f1(arg) + @f2 + class Foo: pass + +is roughly equivalent to + + class Foo: pass + Foo = f1(arg)(f2(Foo)) + +The evaluation rules for the decorator expressions are the same as for +function decorators. The result is then bound to the class name. + +Changed in version 3.9: Classes may be decorated with any valid +"assignment_expression". Previously, the grammar was much more +restrictive; see **PEP 614** for details. + +A list of type parameters may be given in square brackets immediately +after the class’s name. This indicates to static type checkers that +the class is generic. At runtime, the type parameters can be retrieved +from the class’s "__type_params__" attribute. See Generic classes for +more. + +Changed in version 3.12: Type parameter lists are new in Python 3.12. + +**Programmer’s note:** Variables defined in the class definition are +class attributes; they are shared by instances. Instance attributes +can be set in a method with "self.name = value". Both class and +instance attributes are accessible through the notation “"self.name"”, +and an instance attribute hides a class attribute with the same name +when accessed in this way. Class attributes can be used as defaults +for instance attributes, but using mutable values there can lead to +unexpected results. Descriptors can be used to create instance +variables with different implementation details. + +See also: + + **PEP 3115** - Metaclasses in Python 3000 + The proposal that changed the declaration of metaclasses to the + current syntax, and the semantics for how classes with + metaclasses are constructed. + + **PEP 3129** - Class Decorators + The proposal that added class decorators. Function and method + decorators were introduced in **PEP 318**. +''', + 'comparisons': r'''Comparisons +*********** + +Unlike C, all comparison operations in Python have the same priority, +which is lower than that of any arithmetic, shifting or bitwise +operation. Also unlike C, expressions like "a < b < c" have the +interpretation that is conventional in mathematics: + + comparison ::= or_expr (comp_operator or_expr)* + comp_operator ::= "<" | ">" | "==" | ">=" | "<=" | "!=" + | "is" ["not"] | ["not"] "in" + +Comparisons yield boolean values: "True" or "False". Custom *rich +comparison methods* may return non-boolean values. In this case Python +will call "bool()" on such value in boolean contexts. + +Comparisons can be chained arbitrarily, e.g., "x < y <= z" is +equivalent to "x < y and y <= z", except that "y" is evaluated only +once (but in both cases "z" is not evaluated at all when "x < y" is +found to be false). + +Formally, if *a*, *b*, *c*, …, *y*, *z* are expressions and *op1*, +*op2*, …, *opN* are comparison operators, then "a op1 b op2 c ... y +opN z" is equivalent to "a op1 b and b op2 c and ... y opN z", except +that each expression is evaluated at most once. + +Note that "a op1 b op2 c" doesn’t imply any kind of comparison between +*a* and *c*, so that, e.g., "x < y > z" is perfectly legal (though +perhaps not pretty). + + +Value comparisons +================= + +The operators "<", ">", "==", ">=", "<=", and "!=" compare the values +of two objects. The objects do not need to have the same type. + +Chapter Objects, values and types states that objects have a value (in +addition to type and identity). The value of an object is a rather +abstract notion in Python: For example, there is no canonical access +method for an object’s value. Also, there is no requirement that the +value of an object should be constructed in a particular way, e.g. +comprised of all its data attributes. Comparison operators implement a +particular notion of what the value of an object is. One can think of +them as defining the value of an object indirectly, by means of their +comparison implementation. + +Because all types are (direct or indirect) subtypes of "object", they +inherit the default comparison behavior from "object". Types can +customize their comparison behavior by implementing *rich comparison +methods* like "__lt__()", described in Basic customization. + +The default behavior for equality comparison ("==" and "!=") is based +on the identity of the objects. Hence, equality comparison of +instances with the same identity results in equality, and equality +comparison of instances with different identities results in +inequality. A motivation for this default behavior is the desire that +all objects should be reflexive (i.e. "x is y" implies "x == y"). + +A default order comparison ("<", ">", "<=", and ">=") is not provided; +an attempt raises "TypeError". A motivation for this default behavior +is the lack of a similar invariant as for equality. + +The behavior of the default equality comparison, that instances with +different identities are always unequal, may be in contrast to what +types will need that have a sensible definition of object value and +value-based equality. Such types will need to customize their +comparison behavior, and in fact, a number of built-in types have done +that. + +The following list describes the comparison behavior of the most +important built-in types. + +* Numbers of built-in numeric types (Numeric Types — int, float, + complex) and of the standard library types "fractions.Fraction" and + "decimal.Decimal" can be compared within and across their types, + with the restriction that complex numbers do not support order + comparison. Within the limits of the types involved, they compare + mathematically (algorithmically) correct without loss of precision. + + The not-a-number values "float('NaN')" and "decimal.Decimal('NaN')" + are special. Any ordered comparison of a number to a not-a-number + value is false. A counter-intuitive implication is that not-a-number + values are not equal to themselves. For example, if "x = + float('NaN')", "3 < x", "x < 3" and "x == x" are all false, while "x + != x" is true. This behavior is compliant with IEEE 754. + +* "None" and "NotImplemented" are singletons. **PEP 8** advises that + comparisons for singletons should always be done with "is" or "is + not", never the equality operators. + +* Binary sequences (instances of "bytes" or "bytearray") can be + compared within and across their types. They compare + lexicographically using the numeric values of their elements. + +* Strings (instances of "str") compare lexicographically using the + numerical Unicode code points (the result of the built-in function + "ord()") of their characters. [3] + + Strings and binary sequences cannot be directly compared. + +* Sequences (instances of "tuple", "list", or "range") can be compared + only within each of their types, with the restriction that ranges do + not support order comparison. Equality comparison across these + types results in inequality, and ordering comparison across these + types raises "TypeError". + + Sequences compare lexicographically using comparison of + corresponding elements. The built-in containers typically assume + identical objects are equal to themselves. That lets them bypass + equality tests for identical objects to improve performance and to + maintain their internal invariants. + + Lexicographical comparison between built-in collections works as + follows: + + * For two collections to compare equal, they must be of the same + type, have the same length, and each pair of corresponding + elements must compare equal (for example, "[1,2] == (1,2)" is + false because the type is not the same). + + * Collections that support order comparison are ordered the same as + their first unequal elements (for example, "[1,2,x] <= [1,2,y]" + has the same value as "x <= y"). If a corresponding element does + not exist, the shorter collection is ordered first (for example, + "[1,2] < [1,2,3]" is true). + +* Mappings (instances of "dict") compare equal if and only if they + have equal "(key, value)" pairs. Equality comparison of the keys and + values enforces reflexivity. + + Order comparisons ("<", ">", "<=", and ">=") raise "TypeError". + +* Sets (instances of "set" or "frozenset") can be compared within and + across their types. + + They define order comparison operators to mean subset and superset + tests. Those relations do not define total orderings (for example, + the two sets "{1,2}" and "{2,3}" are not equal, nor subsets of one + another, nor supersets of one another). Accordingly, sets are not + appropriate arguments for functions which depend on total ordering + (for example, "min()", "max()", and "sorted()" produce undefined + results given a list of sets as inputs). + + Comparison of sets enforces reflexivity of its elements. + +* Most other built-in types have no comparison methods implemented, so + they inherit the default comparison behavior. + +User-defined classes that customize their comparison behavior should +follow some consistency rules, if possible: + +* Equality comparison should be reflexive. In other words, identical + objects should compare equal: + + "x is y" implies "x == y" + +* Comparison should be symmetric. In other words, the following + expressions should have the same result: + + "x == y" and "y == x" + + "x != y" and "y != x" + + "x < y" and "y > x" + + "x <= y" and "y >= x" + +* Comparison should be transitive. The following (non-exhaustive) + examples illustrate that: + + "x > y and y > z" implies "x > z" + + "x < y and y <= z" implies "x < z" + +* Inverse comparison should result in the boolean negation. In other + words, the following expressions should have the same result: + + "x == y" and "not x != y" + + "x < y" and "not x >= y" (for total ordering) + + "x > y" and "not x <= y" (for total ordering) + + The last two expressions apply to totally ordered collections (e.g. + to sequences, but not to sets or mappings). See also the + "total_ordering()" decorator. + +* The "hash()" result should be consistent with equality. Objects that + are equal should either have the same hash value, or be marked as + unhashable. + +Python does not enforce these consistency rules. In fact, the +not-a-number values are an example for not following these rules. + + +Membership test operations +========================== + +The operators "in" and "not in" test for membership. "x in s" +evaluates to "True" if *x* is a member of *s*, and "False" otherwise. +"x not in s" returns the negation of "x in s". All built-in sequences +and set types support this as well as dictionary, for which "in" tests +whether the dictionary has a given key. For container types such as +list, tuple, set, frozenset, dict, or collections.deque, the +expression "x in y" is equivalent to "any(x is e or x == e for e in +y)". + +For the string and bytes types, "x in y" is "True" if and only if *x* +is a substring of *y*. An equivalent test is "y.find(x) != -1". +Empty strings are always considered to be a substring of any other +string, so """ in "abc"" will return "True". + +For user-defined classes which define the "__contains__()" method, "x +in y" returns "True" if "y.__contains__(x)" returns a true value, and +"False" otherwise. + +For user-defined classes which do not define "__contains__()" but do +define "__iter__()", "x in y" is "True" if some value "z", for which +the expression "x is z or x == z" is true, is produced while iterating +over "y". If an exception is raised during the iteration, it is as if +"in" raised that exception. + +Lastly, the old-style iteration protocol is tried: if a class defines +"__getitem__()", "x in y" is "True" if and only if there is a non- +negative integer index *i* such that "x is y[i] or x == y[i]", and no +lower integer index raises the "IndexError" exception. (If any other +exception is raised, it is as if "in" raised that exception). + +The operator "not in" is defined to have the inverse truth value of +"in". + + +Identity comparisons +==================== + +The operators "is" and "is not" test for an object’s identity: "x is +y" is true if and only if *x* and *y* are the same object. An +Object’s identity is determined using the "id()" function. "x is not +y" yields the inverse truth value. [4] +''', + 'compound': r'''Compound statements +******************* + +Compound statements contain (groups of) other statements; they affect +or control the execution of those other statements in some way. In +general, compound statements span multiple lines, although in simple +incarnations a whole compound statement may be contained in one line. + +The "if", "while" and "for" statements implement traditional control +flow constructs. "try" specifies exception handlers and/or cleanup +code for a group of statements, while the "with" statement allows the +execution of initialization and finalization code around a block of +code. Function and class definitions are also syntactically compound +statements. + +A compound statement consists of one or more ‘clauses.’ A clause +consists of a header and a ‘suite.’ The clause headers of a +particular compound statement are all at the same indentation level. +Each clause header begins with a uniquely identifying keyword and ends +with a colon. A suite is a group of statements controlled by a +clause. A suite can be one or more semicolon-separated simple +statements on the same line as the header, following the header’s +colon, or it can be one or more indented statements on subsequent +lines. Only the latter form of a suite can contain nested compound +statements; the following is illegal, mostly because it wouldn’t be +clear to which "if" clause a following "else" clause would belong: + + if test1: if test2: print(x) + +Also note that the semicolon binds tighter than the colon in this +context, so that in the following example, either all or none of the +"print()" calls are executed: + + if x < y < z: print(x); print(y); print(z) + +Summarizing: + + compound_stmt ::= if_stmt + | while_stmt + | for_stmt + | try_stmt + | with_stmt + | match_stmt + | funcdef + | classdef + | async_with_stmt + | async_for_stmt + | async_funcdef + suite ::= stmt_list NEWLINE | NEWLINE INDENT statement+ DEDENT + statement ::= stmt_list NEWLINE | compound_stmt + stmt_list ::= simple_stmt (";" simple_stmt)* [";"] + +Note that statements always end in a "NEWLINE" possibly followed by a +"DEDENT". Also note that optional continuation clauses always begin +with a keyword that cannot start a statement, thus there are no +ambiguities (the ‘dangling "else"’ problem is solved in Python by +requiring nested "if" statements to be indented). + +The formatting of the grammar rules in the following sections places +each clause on a separate line for clarity. + + +The "if" statement +================== + +The "if" statement is used for conditional execution: + + if_stmt ::= "if" assignment_expression ":" suite + ("elif" assignment_expression ":" suite)* + ["else" ":" suite] + +It selects exactly one of the suites by evaluating the expressions one +by one until one is found to be true (see section Boolean operations +for the definition of true and false); then that suite is executed +(and no other part of the "if" statement is executed or evaluated). +If all expressions are false, the suite of the "else" clause, if +present, is executed. + + +The "while" statement +===================== + +The "while" statement is used for repeated execution as long as an +expression is true: + + while_stmt ::= "while" assignment_expression ":" suite + ["else" ":" suite] + +This repeatedly tests the expression and, if it is true, executes the +first suite; if the expression is false (which may be the first time +it is tested) the suite of the "else" clause, if present, is executed +and the loop terminates. + +A "break" statement executed in the first suite terminates the loop +without executing the "else" clause’s suite. A "continue" statement +executed in the first suite skips the rest of the suite and goes back +to testing the expression. + + +The "for" statement +=================== + +The "for" statement is used to iterate over the elements of a sequence +(such as a string, tuple or list) or other iterable object: + + for_stmt ::= "for" target_list "in" starred_list ":" suite + ["else" ":" suite] + +The "starred_list" expression is evaluated once; it should yield an +*iterable* object. An *iterator* is created for that iterable. The +first item provided by the iterator is then assigned to the target +list using the standard rules for assignments (see Assignment +statements), and the suite is executed. This repeats for each item +provided by the iterator. When the iterator is exhausted, the suite +in the "else" clause, if present, is executed, and the loop +terminates. + +A "break" statement executed in the first suite terminates the loop +without executing the "else" clause’s suite. A "continue" statement +executed in the first suite skips the rest of the suite and continues +with the next item, or with the "else" clause if there is no next +item. + +The for-loop makes assignments to the variables in the target list. +This overwrites all previous assignments to those variables including +those made in the suite of the for-loop: + + for i in range(10): + print(i) + i = 5 # this will not affect the for-loop + # because i will be overwritten with the next + # index in the range + +Names in the target list are not deleted when the loop is finished, +but if the sequence is empty, they will not have been assigned to at +all by the loop. Hint: the built-in type "range()" represents +immutable arithmetic sequences of integers. For instance, iterating +"range(3)" successively yields 0, 1, and then 2. + +Changed in version 3.11: Starred elements are now allowed in the +expression list. + + +The "try" statement +=================== + +The "try" statement specifies exception handlers and/or cleanup code +for a group of statements: + + try_stmt ::= try1_stmt | try2_stmt | try3_stmt + try1_stmt ::= "try" ":" suite + ("except" [expression ["as" identifier]] ":" suite)+ + ["else" ":" suite] + ["finally" ":" suite] + try2_stmt ::= "try" ":" suite + ("except" "*" expression ["as" identifier] ":" suite)+ + ["else" ":" suite] + ["finally" ":" suite] + try3_stmt ::= "try" ":" suite + "finally" ":" suite + +Additional information on exceptions can be found in section +Exceptions, and information on using the "raise" statement to generate +exceptions may be found in section The raise statement. + + +"except" clause +--------------- + +The "except" clause(s) specify one or more exception handlers. When no +exception occurs in the "try" clause, no exception handler is +executed. When an exception occurs in the "try" suite, a search for an +exception handler is started. This search inspects the "except" +clauses in turn until one is found that matches the exception. An +expression-less "except" clause, if present, must be last; it matches +any exception. + +For an "except" clause with an expression, the expression must +evaluate to an exception type or a tuple of exception types. The +raised exception matches an "except" clause whose expression evaluates +to the class or a *non-virtual base class* of the exception object, or +to a tuple that contains such a class. + +If no "except" clause matches the exception, the search for an +exception handler continues in the surrounding code and on the +invocation stack. [1] + +If the evaluation of an expression in the header of an "except" clause +raises an exception, the original search for a handler is canceled and +a search starts for the new exception in the surrounding code and on +the call stack (it is treated as if the entire "try" statement raised +the exception). + +When a matching "except" clause is found, the exception is assigned to +the target specified after the "as" keyword in that "except" clause, +if present, and the "except" clause’s suite is executed. All "except" +clauses must have an executable block. When the end of this block is +reached, execution continues normally after the entire "try" +statement. (This means that if two nested handlers exist for the same +exception, and the exception occurs in the "try" clause of the inner +handler, the outer handler will not handle the exception.) + +When an exception has been assigned using "as target", it is cleared +at the end of the "except" clause. This is as if + + except E as N: + foo + +was translated to + + except E as N: + try: + foo + finally: + del N + +This means the exception must be assigned to a different name to be +able to refer to it after the "except" clause. Exceptions are cleared +because with the traceback attached to them, they form a reference +cycle with the stack frame, keeping all locals in that frame alive +until the next garbage collection occurs. + +Before an "except" clause’s suite is executed, the exception is stored +in the "sys" module, where it can be accessed from within the body of +the "except" clause by calling "sys.exception()". When leaving an +exception handler, the exception stored in the "sys" module is reset +to its previous value: + + >>> print(sys.exception()) + None + >>> try: + ... raise TypeError + ... except: + ... print(repr(sys.exception())) + ... try: + ... raise ValueError + ... except: + ... print(repr(sys.exception())) + ... print(repr(sys.exception())) + ... + TypeError() + ValueError() + TypeError() + >>> print(sys.exception()) + None + + +"except*" clause +---------------- + +The "except*" clause(s) are used for handling "ExceptionGroup"s. The +exception type for matching is interpreted as in the case of "except", +but in the case of exception groups we can have partial matches when +the type matches some of the exceptions in the group. This means that +multiple "except*" clauses can execute, each handling part of the +exception group. Each clause executes at most once and handles an +exception group of all matching exceptions. Each exception in the +group is handled by at most one "except*" clause, the first that +matches it. + + >>> try: + ... raise ExceptionGroup("eg", + ... [ValueError(1), TypeError(2), OSError(3), OSError(4)]) + ... except* TypeError as e: + ... print(f'caught {type(e)} with nested {e.exceptions}') + ... except* OSError as e: + ... print(f'caught {type(e)} with nested {e.exceptions}') + ... + caught <class 'ExceptionGroup'> with nested (TypeError(2),) + caught <class 'ExceptionGroup'> with nested (OSError(3), OSError(4)) + + Exception Group Traceback (most recent call last): + | File "<stdin>", line 2, in <module> + | ExceptionGroup: eg + +-+---------------- 1 ---------------- + | ValueError: 1 + +------------------------------------ + +Any remaining exceptions that were not handled by any "except*" clause +are re-raised at the end, along with all exceptions that were raised +from within the "except*" clauses. If this list contains more than one +exception to reraise, they are combined into an exception group. + +If the raised exception is not an exception group and its type matches +one of the "except*" clauses, it is caught and wrapped by an exception +group with an empty message string. + + >>> try: + ... raise BlockingIOError + ... except* BlockingIOError as e: + ... print(repr(e)) + ... + ExceptionGroup('', (BlockingIOError())) + +An "except*" clause must have a matching expression; it cannot be +"except*:". Furthermore, this expression cannot contain exception +group types, because that would have ambiguous semantics. + +It is not possible to mix "except" and "except*" in the same "try". +"break", "continue" and "return" cannot appear in an "except*" clause. + + +"else" clause +------------- + +The optional "else" clause is executed if the control flow leaves the +"try" suite, no exception was raised, and no "return", "continue", or +"break" statement was executed. Exceptions in the "else" clause are +not handled by the preceding "except" clauses. + + +"finally" clause +---------------- + +If "finally" is present, it specifies a ‘cleanup’ handler. The "try" +clause is executed, including any "except" and "else" clauses. If an +exception occurs in any of the clauses and is not handled, the +exception is temporarily saved. The "finally" clause is executed. If +there is a saved exception it is re-raised at the end of the "finally" +clause. If the "finally" clause raises another exception, the saved +exception is set as the context of the new exception. If the "finally" +clause executes a "return", "break" or "continue" statement, the saved +exception is discarded: + + >>> def f(): + ... try: + ... 1/0 + ... finally: + ... return 42 + ... + >>> f() + 42 + +The exception information is not available to the program during +execution of the "finally" clause. + +When a "return", "break" or "continue" statement is executed in the +"try" suite of a "try"…"finally" statement, the "finally" clause is +also executed ‘on the way out.’ + +The return value of a function is determined by the last "return" +statement executed. Since the "finally" clause always executes, a +"return" statement executed in the "finally" clause will always be the +last one executed: + + >>> def foo(): + ... try: + ... return 'try' + ... finally: + ... return 'finally' + ... + >>> foo() + 'finally' + +Changed in version 3.8: Prior to Python 3.8, a "continue" statement +was illegal in the "finally" clause due to a problem with the +implementation. + + +The "with" statement +==================== + +The "with" statement is used to wrap the execution of a block with +methods defined by a context manager (see section With Statement +Context Managers). This allows common "try"…"except"…"finally" usage +patterns to be encapsulated for convenient reuse. + + with_stmt ::= "with" ( "(" with_stmt_contents ","? ")" | with_stmt_contents ) ":" suite + with_stmt_contents ::= with_item ("," with_item)* + with_item ::= expression ["as" target] + +The execution of the "with" statement with one “item” proceeds as +follows: + +1. The context expression (the expression given in the "with_item") is + evaluated to obtain a context manager. + +2. The context manager’s "__enter__()" is loaded for later use. + +3. The context manager’s "__exit__()" is loaded for later use. + +4. The context manager’s "__enter__()" method is invoked. + +5. If a target was included in the "with" statement, the return value + from "__enter__()" is assigned to it. + + Note: + + The "with" statement guarantees that if the "__enter__()" method + returns without an error, then "__exit__()" will always be + called. Thus, if an error occurs during the assignment to the + target list, it will be treated the same as an error occurring + within the suite would be. See step 7 below. + +6. The suite is executed. + +7. The context manager’s "__exit__()" method is invoked. If an + exception caused the suite to be exited, its type, value, and + traceback are passed as arguments to "__exit__()". Otherwise, three + "None" arguments are supplied. + + If the suite was exited due to an exception, and the return value + from the "__exit__()" method was false, the exception is reraised. + If the return value was true, the exception is suppressed, and + execution continues with the statement following the "with" + statement. + + If the suite was exited for any reason other than an exception, the + return value from "__exit__()" is ignored, and execution proceeds + at the normal location for the kind of exit that was taken. + +The following code: + + with EXPRESSION as TARGET: + SUITE + +is semantically equivalent to: + + manager = (EXPRESSION) + enter = type(manager).__enter__ + exit = type(manager).__exit__ + value = enter(manager) + hit_except = False + + try: + TARGET = value + SUITE + except: + hit_except = True + if not exit(manager, *sys.exc_info()): + raise + finally: + if not hit_except: + exit(manager, None, None, None) + +With more than one item, the context managers are processed as if +multiple "with" statements were nested: + + with A() as a, B() as b: + SUITE + +is semantically equivalent to: + + with A() as a: + with B() as b: + SUITE + +You can also write multi-item context managers in multiple lines if +the items are surrounded by parentheses. For example: + + with ( + A() as a, + B() as b, + ): + SUITE + +Changed in version 3.1: Support for multiple context expressions. + +Changed in version 3.10: Support for using grouping parentheses to +break the statement in multiple lines. + +See also: + + **PEP 343** - The “with” statement + The specification, background, and examples for the Python "with" + statement. + + +The "match" statement +===================== + +Added in version 3.10. + +The match statement is used for pattern matching. Syntax: + + match_stmt ::= 'match' subject_expr ":" NEWLINE INDENT case_block+ DEDENT + subject_expr ::= star_named_expression "," star_named_expressions? + | named_expression + case_block ::= 'case' patterns [guard] ":" block + +Note: + + This section uses single quotes to denote soft keywords. + +Pattern matching takes a pattern as input (following "case") and a +subject value (following "match"). The pattern (which may contain +subpatterns) is matched against the subject value. The outcomes are: + +* A match success or failure (also termed a pattern success or + failure). + +* Possible binding of matched values to a name. The prerequisites for + this are further discussed below. + +The "match" and "case" keywords are soft keywords. + +See also: + + * **PEP 634** – Structural Pattern Matching: Specification + + * **PEP 636** – Structural Pattern Matching: Tutorial + + +Overview +-------- + +Here’s an overview of the logical flow of a match statement: + +1. The subject expression "subject_expr" is evaluated and a resulting + subject value obtained. If the subject expression contains a comma, + a tuple is constructed using the standard rules. + +2. Each pattern in a "case_block" is attempted to match with the + subject value. The specific rules for success or failure are + described below. The match attempt can also bind some or all of the + standalone names within the pattern. The precise pattern binding + rules vary per pattern type and are specified below. **Name + bindings made during a successful pattern match outlive the + executed block and can be used after the match statement**. + + Note: + + During failed pattern matches, some subpatterns may succeed. Do + not rely on bindings being made for a failed match. Conversely, + do not rely on variables remaining unchanged after a failed + match. The exact behavior is dependent on implementation and may + vary. This is an intentional decision made to allow different + implementations to add optimizations. + +3. If the pattern succeeds, the corresponding guard (if present) is + evaluated. In this case all name bindings are guaranteed to have + happened. + + * If the guard evaluates as true or is missing, the "block" inside + "case_block" is executed. + + * Otherwise, the next "case_block" is attempted as described above. + + * If there are no further case blocks, the match statement is + completed. + +Note: + + Users should generally never rely on a pattern being evaluated. + Depending on implementation, the interpreter may cache values or use + other optimizations which skip repeated evaluations. + +A sample match statement: + + >>> flag = False + >>> match (100, 200): + ... case (100, 300): # Mismatch: 200 != 300 + ... print('Case 1') + ... case (100, 200) if flag: # Successful match, but guard fails + ... print('Case 2') + ... case (100, y): # Matches and binds y to 200 + ... print(f'Case 3, y: {y}') + ... case _: # Pattern not attempted + ... print('Case 4, I match anything!') + ... + Case 3, y: 200 + +In this case, "if flag" is a guard. Read more about that in the next +section. + + +Guards +------ + + guard ::= "if" named_expression + +A "guard" (which is part of the "case") must succeed for code inside +the "case" block to execute. It takes the form: "if" followed by an +expression. + +The logical flow of a "case" block with a "guard" follows: + +1. Check that the pattern in the "case" block succeeded. If the + pattern failed, the "guard" is not evaluated and the next "case" + block is checked. + +2. If the pattern succeeded, evaluate the "guard". + + * If the "guard" condition evaluates as true, the case block is + selected. + + * If the "guard" condition evaluates as false, the case block is + not selected. + + * If the "guard" raises an exception during evaluation, the + exception bubbles up. + +Guards are allowed to have side effects as they are expressions. +Guard evaluation must proceed from the first to the last case block, +one at a time, skipping case blocks whose pattern(s) don’t all +succeed. (I.e., guard evaluation must happen in order.) Guard +evaluation must stop once a case block is selected. + + +Irrefutable Case Blocks +----------------------- + +An irrefutable case block is a match-all case block. A match +statement may have at most one irrefutable case block, and it must be +last. + +A case block is considered irrefutable if it has no guard and its +pattern is irrefutable. A pattern is considered irrefutable if we can +prove from its syntax alone that it will always succeed. Only the +following patterns are irrefutable: + +* AS Patterns whose left-hand side is irrefutable + +* OR Patterns containing at least one irrefutable pattern + +* Capture Patterns + +* Wildcard Patterns + +* parenthesized irrefutable patterns + + +Patterns +-------- + +Note: + + This section uses grammar notations beyond standard EBNF: + + * the notation "SEP.RULE+" is shorthand for "RULE (SEP RULE)*" + + * the notation "!RULE" is shorthand for a negative lookahead + assertion + +The top-level syntax for "patterns" is: + + patterns ::= open_sequence_pattern | pattern + pattern ::= as_pattern | or_pattern + closed_pattern ::= | literal_pattern + | capture_pattern + | wildcard_pattern + | value_pattern + | group_pattern + | sequence_pattern + | mapping_pattern + | class_pattern + +The descriptions below will include a description “in simple terms” of +what a pattern does for illustration purposes (credits to Raymond +Hettinger for a document that inspired most of the descriptions). Note +that these descriptions are purely for illustration purposes and **may +not** reflect the underlying implementation. Furthermore, they do not +cover all valid forms. + + +OR Patterns +~~~~~~~~~~~ + +An OR pattern is two or more patterns separated by vertical bars "|". +Syntax: + + or_pattern ::= "|".closed_pattern+ + +Only the final subpattern may be irrefutable, and each subpattern must +bind the same set of names to avoid ambiguity. + +An OR pattern matches each of its subpatterns in turn to the subject +value, until one succeeds. The OR pattern is then considered +successful. Otherwise, if none of the subpatterns succeed, the OR +pattern fails. + +In simple terms, "P1 | P2 | ..." will try to match "P1", if it fails +it will try to match "P2", succeeding immediately if any succeeds, +failing otherwise. + + +AS Patterns +~~~~~~~~~~~ + +An AS pattern matches an OR pattern on the left of the "as" keyword +against a subject. Syntax: + + as_pattern ::= or_pattern "as" capture_pattern + +If the OR pattern fails, the AS pattern fails. Otherwise, the AS +pattern binds the subject to the name on the right of the as keyword +and succeeds. "capture_pattern" cannot be a "_". + +In simple terms "P as NAME" will match with "P", and on success it +will set "NAME = <subject>". + + +Literal Patterns +~~~~~~~~~~~~~~~~ + +A literal pattern corresponds to most literals in Python. Syntax: + + literal_pattern ::= signed_number + | signed_number "+" NUMBER + | signed_number "-" NUMBER + | strings + | "None" + | "True" + | "False" + signed_number ::= ["-"] NUMBER + +The rule "strings" and the token "NUMBER" are defined in the standard +Python grammar. Triple-quoted strings are supported. Raw strings and +byte strings are supported. f-strings are not supported. + +The forms "signed_number '+' NUMBER" and "signed_number '-' NUMBER" +are for expressing complex numbers; they require a real number on the +left and an imaginary number on the right. E.g. "3 + 4j". + +In simple terms, "LITERAL" will succeed only if "<subject> == +LITERAL". For the singletons "None", "True" and "False", the "is" +operator is used. + + +Capture Patterns +~~~~~~~~~~~~~~~~ + +A capture pattern binds the subject value to a name. Syntax: + + capture_pattern ::= !'_' NAME + +A single underscore "_" is not a capture pattern (this is what "!'_'" +expresses). It is instead treated as a "wildcard_pattern". + +In a given pattern, a given name can only be bound once. E.g. "case +x, x: ..." is invalid while "case [x] | x: ..." is allowed. + +Capture patterns always succeed. The binding follows scoping rules +established by the assignment expression operator in **PEP 572**; the +name becomes a local variable in the closest containing function scope +unless there’s an applicable "global" or "nonlocal" statement. + +In simple terms "NAME" will always succeed and it will set "NAME = +<subject>". + + +Wildcard Patterns +~~~~~~~~~~~~~~~~~ + +A wildcard pattern always succeeds (matches anything) and binds no +name. Syntax: + + wildcard_pattern ::= '_' + +"_" is a soft keyword within any pattern, but only within patterns. +It is an identifier, as usual, even within "match" subject +expressions, "guard"s, and "case" blocks. + +In simple terms, "_" will always succeed. + + +Value Patterns +~~~~~~~~~~~~~~ + +A value pattern represents a named value in Python. Syntax: + + value_pattern ::= attr + attr ::= name_or_attr "." NAME + name_or_attr ::= attr | NAME + +The dotted name in the pattern is looked up using standard Python name +resolution rules. The pattern succeeds if the value found compares +equal to the subject value (using the "==" equality operator). + +In simple terms "NAME1.NAME2" will succeed only if "<subject> == +NAME1.NAME2" + +Note: + + If the same value occurs multiple times in the same match statement, + the interpreter may cache the first value found and reuse it rather + than repeat the same lookup. This cache is strictly tied to a given + execution of a given match statement. + + +Group Patterns +~~~~~~~~~~~~~~ + +A group pattern allows users to add parentheses around patterns to +emphasize the intended grouping. Otherwise, it has no additional +syntax. Syntax: + + group_pattern ::= "(" pattern ")" + +In simple terms "(P)" has the same effect as "P". + + +Sequence Patterns +~~~~~~~~~~~~~~~~~ + +A sequence pattern contains several subpatterns to be matched against +sequence elements. The syntax is similar to the unpacking of a list or +tuple. + + sequence_pattern ::= "[" [maybe_sequence_pattern] "]" + | "(" [open_sequence_pattern] ")" + open_sequence_pattern ::= maybe_star_pattern "," [maybe_sequence_pattern] + maybe_sequence_pattern ::= ",".maybe_star_pattern+ ","? + maybe_star_pattern ::= star_pattern | pattern + star_pattern ::= "*" (capture_pattern | wildcard_pattern) + +There is no difference if parentheses or square brackets are used for +sequence patterns (i.e. "(...)" vs "[...]" ). + +Note: + + A single pattern enclosed in parentheses without a trailing comma + (e.g. "(3 | 4)") is a group pattern. While a single pattern enclosed + in square brackets (e.g. "[3 | 4]") is still a sequence pattern. + +At most one star subpattern may be in a sequence pattern. The star +subpattern may occur in any position. If no star subpattern is +present, the sequence pattern is a fixed-length sequence pattern; +otherwise it is a variable-length sequence pattern. + +The following is the logical flow for matching a sequence pattern +against a subject value: + +1. If the subject value is not a sequence [2], the sequence pattern + fails. + +2. If the subject value is an instance of "str", "bytes" or + "bytearray" the sequence pattern fails. + +3. The subsequent steps depend on whether the sequence pattern is + fixed or variable-length. + + If the sequence pattern is fixed-length: + + 1. If the length of the subject sequence is not equal to the number + of subpatterns, the sequence pattern fails + + 2. Subpatterns in the sequence pattern are matched to their + corresponding items in the subject sequence from left to right. + Matching stops as soon as a subpattern fails. If all + subpatterns succeed in matching their corresponding item, the + sequence pattern succeeds. + + Otherwise, if the sequence pattern is variable-length: + + 1. If the length of the subject sequence is less than the number of + non-star subpatterns, the sequence pattern fails. + + 2. The leading non-star subpatterns are matched to their + corresponding items as for fixed-length sequences. + + 3. If the previous step succeeds, the star subpattern matches a + list formed of the remaining subject items, excluding the + remaining items corresponding to non-star subpatterns following + the star subpattern. + + 4. Remaining non-star subpatterns are matched to their + corresponding subject items, as for a fixed-length sequence. + + Note: + + The length of the subject sequence is obtained via "len()" (i.e. + via the "__len__()" protocol). This length may be cached by the + interpreter in a similar manner as value patterns. + +In simple terms "[P1, P2, P3," … ", P<N>]" matches only if all the +following happens: + +* check "<subject>" is a sequence + +* "len(subject) == <N>" + +* "P1" matches "<subject>[0]" (note that this match can also bind + names) + +* "P2" matches "<subject>[1]" (note that this match can also bind + names) + +* … and so on for the corresponding pattern/element. + + +Mapping Patterns +~~~~~~~~~~~~~~~~ + +A mapping pattern contains one or more key-value patterns. The syntax +is similar to the construction of a dictionary. Syntax: + + mapping_pattern ::= "{" [items_pattern] "}" + items_pattern ::= ",".key_value_pattern+ ","? + key_value_pattern ::= (literal_pattern | value_pattern) ":" pattern + | double_star_pattern + double_star_pattern ::= "**" capture_pattern + +At most one double star pattern may be in a mapping pattern. The +double star pattern must be the last subpattern in the mapping +pattern. + +Duplicate keys in mapping patterns are disallowed. Duplicate literal +keys will raise a "SyntaxError". Two keys that otherwise have the same +value will raise a "ValueError" at runtime. + +The following is the logical flow for matching a mapping pattern +against a subject value: + +1. If the subject value is not a mapping [3],the mapping pattern + fails. + +2. If every key given in the mapping pattern is present in the subject + mapping, and the pattern for each key matches the corresponding + item of the subject mapping, the mapping pattern succeeds. + +3. If duplicate keys are detected in the mapping pattern, the pattern + is considered invalid. A "SyntaxError" is raised for duplicate + literal values; or a "ValueError" for named keys of the same value. + +Note: + + Key-value pairs are matched using the two-argument form of the + mapping subject’s "get()" method. Matched key-value pairs must + already be present in the mapping, and not created on-the-fly via + "__missing__()" or "__getitem__()". + +In simple terms "{KEY1: P1, KEY2: P2, ... }" matches only if all the +following happens: + +* check "<subject>" is a mapping + +* "KEY1 in <subject>" + +* "P1" matches "<subject>[KEY1]" + +* … and so on for the corresponding KEY/pattern pair. + + +Class Patterns +~~~~~~~~~~~~~~ + +A class pattern represents a class and its positional and keyword +arguments (if any). Syntax: + + class_pattern ::= name_or_attr "(" [pattern_arguments ","?] ")" + pattern_arguments ::= positional_patterns ["," keyword_patterns] + | keyword_patterns + positional_patterns ::= ",".pattern+ + keyword_patterns ::= ",".keyword_pattern+ + keyword_pattern ::= NAME "=" pattern + +The same keyword should not be repeated in class patterns. + +The following is the logical flow for matching a class pattern against +a subject value: + +1. If "name_or_attr" is not an instance of the builtin "type" , raise + "TypeError". + +2. If the subject value is not an instance of "name_or_attr" (tested + via "isinstance()"), the class pattern fails. + +3. If no pattern arguments are present, the pattern succeeds. + Otherwise, the subsequent steps depend on whether keyword or + positional argument patterns are present. + + For a number of built-in types (specified below), a single + positional subpattern is accepted which will match the entire + subject; for these types keyword patterns also work as for other + types. + + If only keyword patterns are present, they are processed as + follows, one by one: + + I. The keyword is looked up as an attribute on the subject. + + * If this raises an exception other than "AttributeError", the + exception bubbles up. + + * If this raises "AttributeError", the class pattern has failed. + + * Else, the subpattern associated with the keyword pattern is + matched against the subject’s attribute value. If this fails, + the class pattern fails; if this succeeds, the match proceeds + to the next keyword. + + II. If all keyword patterns succeed, the class pattern succeeds. + + If any positional patterns are present, they are converted to + keyword patterns using the "__match_args__" attribute on the class + "name_or_attr" before matching: + + I. The equivalent of "getattr(cls, "__match_args__", ())" is + called. + + * If this raises an exception, the exception bubbles up. + + * If the returned value is not a tuple, the conversion fails and + "TypeError" is raised. + + * If there are more positional patterns than + "len(cls.__match_args__)", "TypeError" is raised. + + * Otherwise, positional pattern "i" is converted to a keyword + pattern using "__match_args__[i]" as the keyword. + "__match_args__[i]" must be a string; if not "TypeError" is + raised. + + * If there are duplicate keywords, "TypeError" is raised. + + See also: + + Customizing positional arguments in class pattern matching + + II. Once all positional patterns have been converted to keyword + patterns, + the match proceeds as if there were only keyword patterns. + + For the following built-in types the handling of positional + subpatterns is different: + + * "bool" + + * "bytearray" + + * "bytes" + + * "dict" + + * "float" + + * "frozenset" + + * "int" + + * "list" + + * "set" + + * "str" + + * "tuple" + + These classes accept a single positional argument, and the pattern + there is matched against the whole object rather than an attribute. + For example "int(0|1)" matches the value "0", but not the value + "0.0". + +In simple terms "CLS(P1, attr=P2)" matches only if the following +happens: + +* "isinstance(<subject>, CLS)" + +* convert "P1" to a keyword pattern using "CLS.__match_args__" + +* For each keyword argument "attr=P2": + + * "hasattr(<subject>, "attr")" + + * "P2" matches "<subject>.attr" + +* … and so on for the corresponding keyword argument/pattern pair. + +See also: + + * **PEP 634** – Structural Pattern Matching: Specification + + * **PEP 636** – Structural Pattern Matching: Tutorial + + +Function definitions +==================== + +A function definition defines a user-defined function object (see +section The standard type hierarchy): + + funcdef ::= [decorators] "def" funcname [type_params] "(" [parameter_list] ")" + ["->" expression] ":" suite + decorators ::= decorator+ + decorator ::= "@" assignment_expression NEWLINE + parameter_list ::= defparameter ("," defparameter)* "," "/" ["," [parameter_list_no_posonly]] + | parameter_list_no_posonly + parameter_list_no_posonly ::= defparameter ("," defparameter)* ["," [parameter_list_starargs]] + | parameter_list_starargs + parameter_list_starargs ::= "*" [star_parameter] ("," defparameter)* ["," ["**" parameter [","]]] + | "**" parameter [","] + parameter ::= identifier [":" expression] + star_parameter ::= identifier [":" ["*"] expression] + defparameter ::= parameter ["=" expression] + funcname ::= identifier + +A function definition is an executable statement. Its execution binds +the function name in the current local namespace to a function object +(a wrapper around the executable code for the function). This +function object contains a reference to the current global namespace +as the global namespace to be used when the function is called. + +The function definition does not execute the function body; this gets +executed only when the function is called. [4] + +A function definition may be wrapped by one or more *decorator* +expressions. Decorator expressions are evaluated when the function is +defined, in the scope that contains the function definition. The +result must be a callable, which is invoked with the function object +as the only argument. The returned value is bound to the function name +instead of the function object. Multiple decorators are applied in +nested fashion. For example, the following code + + @f1(arg) + @f2 + def func(): pass + +is roughly equivalent to + + def func(): pass + func = f1(arg)(f2(func)) + +except that the original function is not temporarily bound to the name +"func". + +Changed in version 3.9: Functions may be decorated with any valid +"assignment_expression". Previously, the grammar was much more +restrictive; see **PEP 614** for details. + +A list of type parameters may be given in square brackets between the +function’s name and the opening parenthesis for its parameter list. +This indicates to static type checkers that the function is generic. +At runtime, the type parameters can be retrieved from the function’s +"__type_params__" attribute. See Generic functions for more. + +Changed in version 3.12: Type parameter lists are new in Python 3.12. + +When one or more *parameters* have the form *parameter* "=" +*expression*, the function is said to have “default parameter values.” +For a parameter with a default value, the corresponding *argument* may +be omitted from a call, in which case the parameter’s default value is +substituted. If a parameter has a default value, all following +parameters up until the “"*"” must also have a default value — this is +a syntactic restriction that is not expressed by the grammar. + +**Default parameter values are evaluated from left to right when the +function definition is executed.** This means that the expression is +evaluated once, when the function is defined, and that the same “pre- +computed” value is used for each call. This is especially important +to understand when a default parameter value is a mutable object, such +as a list or a dictionary: if the function modifies the object (e.g. +by appending an item to a list), the default parameter value is in +effect modified. This is generally not what was intended. A way +around this is to use "None" as the default, and explicitly test for +it in the body of the function, e.g.: + + def whats_on_the_telly(penguin=None): + if penguin is None: + penguin = [] + penguin.append("property of the zoo") + return penguin + +Function call semantics are described in more detail in section Calls. +A function call always assigns values to all parameters mentioned in +the parameter list, either from positional arguments, from keyword +arguments, or from default values. If the form “"*identifier"” is +present, it is initialized to a tuple receiving any excess positional +parameters, defaulting to the empty tuple. If the form +“"**identifier"” is present, it is initialized to a new ordered +mapping receiving any excess keyword arguments, defaulting to a new +empty mapping of the same type. Parameters after “"*"” or +“"*identifier"” are keyword-only parameters and may only be passed by +keyword arguments. Parameters before “"/"” are positional-only +parameters and may only be passed by positional arguments. + +Changed in version 3.8: The "/" function parameter syntax may be used +to indicate positional-only parameters. See **PEP 570** for details. + +Parameters may have an *annotation* of the form “": expression"” +following the parameter name. Any parameter may have an annotation, +even those of the form "*identifier" or "**identifier". (As a special +case, parameters of the form "*identifier" may have an annotation “": +*expression"”.) Functions may have “return” annotation of the form +“"-> expression"” after the parameter list. These annotations can be +any valid Python expression. The presence of annotations does not +change the semantics of a function. See Annotations for more +information on annotations. + +Changed in version 3.11: Parameters of the form “"*identifier"” may +have an annotation “": *expression"”. See **PEP 646**. + +It is also possible to create anonymous functions (functions not bound +to a name), for immediate use in expressions. This uses lambda +expressions, described in section Lambdas. Note that the lambda +expression is merely a shorthand for a simplified function definition; +a function defined in a “"def"” statement can be passed around or +assigned to another name just like a function defined by a lambda +expression. The “"def"” form is actually more powerful since it +allows the execution of multiple statements and annotations. + +**Programmer’s note:** Functions are first-class objects. A “"def"” +statement executed inside a function definition defines a local +function that can be returned or passed around. Free variables used +in the nested function can access the local variables of the function +containing the def. See section Naming and binding for details. + +See also: + + **PEP 3107** - Function Annotations + The original specification for function annotations. + + **PEP 484** - Type Hints + Definition of a standard meaning for annotations: type hints. + + **PEP 526** - Syntax for Variable Annotations + Ability to type hint variable declarations, including class + variables and instance variables. + + **PEP 563** - Postponed Evaluation of Annotations + Support for forward references within annotations by preserving + annotations in a string form at runtime instead of eager + evaluation. + + **PEP 318** - Decorators for Functions and Methods + Function and method decorators were introduced. Class decorators + were introduced in **PEP 3129**. + + +Class definitions +================= + +A class definition defines a class object (see section The standard +type hierarchy): + + classdef ::= [decorators] "class" classname [type_params] [inheritance] ":" suite + inheritance ::= "(" [argument_list] ")" + classname ::= identifier + +A class definition is an executable statement. The inheritance list +usually gives a list of base classes (see Metaclasses for more +advanced uses), so each item in the list should evaluate to a class +object which allows subclassing. Classes without an inheritance list +inherit, by default, from the base class "object"; hence, + + class Foo: + pass + +is equivalent to + + class Foo(object): + pass + +The class’s suite is then executed in a new execution frame (see +Naming and binding), using a newly created local namespace and the +original global namespace. (Usually, the suite contains mostly +function definitions.) When the class’s suite finishes execution, its +execution frame is discarded but its local namespace is saved. [5] A +class object is then created using the inheritance list for the base +classes and the saved local namespace for the attribute dictionary. +The class name is bound to this class object in the original local +namespace. + +The order in which attributes are defined in the class body is +preserved in the new class’s "__dict__". Note that this is reliable +only right after the class is created and only for classes that were +defined using the definition syntax. + +Class creation can be customized heavily using metaclasses. + +Classes can also be decorated: just like when decorating functions, + + @f1(arg) + @f2 + class Foo: pass + +is roughly equivalent to + + class Foo: pass + Foo = f1(arg)(f2(Foo)) + +The evaluation rules for the decorator expressions are the same as for +function decorators. The result is then bound to the class name. + +Changed in version 3.9: Classes may be decorated with any valid +"assignment_expression". Previously, the grammar was much more +restrictive; see **PEP 614** for details. + +A list of type parameters may be given in square brackets immediately +after the class’s name. This indicates to static type checkers that +the class is generic. At runtime, the type parameters can be retrieved +from the class’s "__type_params__" attribute. See Generic classes for +more. + +Changed in version 3.12: Type parameter lists are new in Python 3.12. + +**Programmer’s note:** Variables defined in the class definition are +class attributes; they are shared by instances. Instance attributes +can be set in a method with "self.name = value". Both class and +instance attributes are accessible through the notation “"self.name"”, +and an instance attribute hides a class attribute with the same name +when accessed in this way. Class attributes can be used as defaults +for instance attributes, but using mutable values there can lead to +unexpected results. Descriptors can be used to create instance +variables with different implementation details. + +See also: + + **PEP 3115** - Metaclasses in Python 3000 + The proposal that changed the declaration of metaclasses to the + current syntax, and the semantics for how classes with + metaclasses are constructed. + + **PEP 3129** - Class Decorators + The proposal that added class decorators. Function and method + decorators were introduced in **PEP 318**. + + +Coroutines +========== + +Added in version 3.5. + + +Coroutine function definition +----------------------------- + + async_funcdef ::= [decorators] "async" "def" funcname "(" [parameter_list] ")" + ["->" expression] ":" suite + +Execution of Python coroutines can be suspended and resumed at many +points (see *coroutine*). "await" expressions, "async for" and "async +with" can only be used in the body of a coroutine function. + +Functions defined with "async def" syntax are always coroutine +functions, even if they do not contain "await" or "async" keywords. + +It is a "SyntaxError" to use a "yield from" expression inside the body +of a coroutine function. + +An example of a coroutine function: + + async def func(param1, param2): + do_stuff() + await some_coroutine() + +Changed in version 3.7: "await" and "async" are now keywords; +previously they were only treated as such inside the body of a +coroutine function. + + +The "async for" statement +------------------------- + + async_for_stmt ::= "async" for_stmt + +An *asynchronous iterable* provides an "__aiter__" method that +directly returns an *asynchronous iterator*, which can call +asynchronous code in its "__anext__" method. + +The "async for" statement allows convenient iteration over +asynchronous iterables. + +The following code: + + async for TARGET in ITER: + SUITE + else: + SUITE2 + +Is semantically equivalent to: + + iter = (ITER) + iter = type(iter).__aiter__(iter) + running = True + + while running: + try: + TARGET = await type(iter).__anext__(iter) + except StopAsyncIteration: + running = False + else: + SUITE + else: + SUITE2 + +See also "__aiter__()" and "__anext__()" for details. + +It is a "SyntaxError" to use an "async for" statement outside the body +of a coroutine function. + + +The "async with" statement +-------------------------- + + async_with_stmt ::= "async" with_stmt + +An *asynchronous context manager* is a *context manager* that is able +to suspend execution in its *enter* and *exit* methods. + +The following code: + + async with EXPRESSION as TARGET: + SUITE + +is semantically equivalent to: + + manager = (EXPRESSION) + aenter = type(manager).__aenter__ + aexit = type(manager).__aexit__ + value = await aenter(manager) + hit_except = False + + try: + TARGET = value + SUITE + except: + hit_except = True + if not await aexit(manager, *sys.exc_info()): + raise + finally: + if not hit_except: + await aexit(manager, None, None, None) + +See also "__aenter__()" and "__aexit__()" for details. + +It is a "SyntaxError" to use an "async with" statement outside the +body of a coroutine function. + +See also: + + **PEP 492** - Coroutines with async and await syntax + The proposal that made coroutines a proper standalone concept in + Python, and added supporting syntax. + + +Type parameter lists +==================== + +Added in version 3.12. + +Changed in version 3.13: Support for default values was added (see +**PEP 696**). + + type_params ::= "[" type_param ("," type_param)* "]" + type_param ::= typevar | typevartuple | paramspec + typevar ::= identifier (":" expression)? ("=" expression)? + typevartuple ::= "*" identifier ("=" expression)? + paramspec ::= "**" identifier ("=" expression)? + +Functions (including coroutines), classes and type aliases may contain +a type parameter list: + + def max[T](args: list[T]) -> T: + ... + + async def amax[T](args: list[T]) -> T: + ... + + class Bag[T]: + def __iter__(self) -> Iterator[T]: + ... + + def add(self, arg: T) -> None: + ... + + type ListOrSet[T] = list[T] | set[T] + +Semantically, this indicates that the function, class, or type alias +is generic over a type variable. This information is primarily used by +static type checkers, and at runtime, generic objects behave much like +their non-generic counterparts. + +Type parameters are declared in square brackets ("[]") immediately +after the name of the function, class, or type alias. The type +parameters are accessible within the scope of the generic object, but +not elsewhere. Thus, after a declaration "def func[T](): pass", the +name "T" is not available in the module scope. Below, the semantics of +generic objects are described with more precision. The scope of type +parameters is modeled with a special function (technically, an +annotation scope) that wraps the creation of the generic object. + +Generic functions, classes, and type aliases have a "__type_params__" +attribute listing their type parameters. + +Type parameters come in three kinds: + +* "typing.TypeVar", introduced by a plain name (e.g., "T"). + Semantically, this represents a single type to a type checker. + +* "typing.TypeVarTuple", introduced by a name prefixed with a single + asterisk (e.g., "*Ts"). Semantically, this stands for a tuple of any + number of types. + +* "typing.ParamSpec", introduced by a name prefixed with two asterisks + (e.g., "**P"). Semantically, this stands for the parameters of a + callable. + +"typing.TypeVar" declarations can define *bounds* and *constraints* +with a colon (":") followed by an expression. A single expression +after the colon indicates a bound (e.g. "T: int"). Semantically, this +means that the "typing.TypeVar" can only represent types that are a +subtype of this bound. A parenthesized tuple of expressions after the +colon indicates a set of constraints (e.g. "T: (str, bytes)"). Each +member of the tuple should be a type (again, this is not enforced at +runtime). Constrained type variables can only take on one of the types +in the list of constraints. + +For "typing.TypeVar"s declared using the type parameter list syntax, +the bound and constraints are not evaluated when the generic object is +created, but only when the value is explicitly accessed through the +attributes "__bound__" and "__constraints__". To accomplish this, the +bounds or constraints are evaluated in a separate annotation scope. + +"typing.TypeVarTuple"s and "typing.ParamSpec"s cannot have bounds or +constraints. + +All three flavors of type parameters can also have a *default value*, +which is used when the type parameter is not explicitly provided. This +is added by appending a single equals sign ("=") followed by an +expression. Like the bounds and constraints of type variables, the +default value is not evaluated when the object is created, but only +when the type parameter’s "__default__" attribute is accessed. To this +end, the default value is evaluated in a separate annotation scope. If +no default value is specified for a type parameter, the "__default__" +attribute is set to the special sentinel object "typing.NoDefault". + +The following example indicates the full set of allowed type parameter +declarations: + + def overly_generic[ + SimpleTypeVar, + TypeVarWithDefault = int, + TypeVarWithBound: int, + TypeVarWithConstraints: (str, bytes), + *SimpleTypeVarTuple = (int, float), + **SimpleParamSpec = (str, bytearray), + ]( + a: SimpleTypeVar, + b: TypeVarWithDefault, + c: TypeVarWithBound, + d: Callable[SimpleParamSpec, TypeVarWithConstraints], + *e: SimpleTypeVarTuple, + ): ... + + +Generic functions +----------------- + +Generic functions are declared as follows: + + def func[T](arg: T): ... + +This syntax is equivalent to: + + annotation-def TYPE_PARAMS_OF_func(): + T = typing.TypeVar("T") + def func(arg: T): ... + func.__type_params__ = (T,) + return func + func = TYPE_PARAMS_OF_func() + +Here "annotation-def" indicates an annotation scope, which is not +actually bound to any name at runtime. (One other liberty is taken in +the translation: the syntax does not go through attribute access on +the "typing" module, but creates an instance of "typing.TypeVar" +directly.) + +The annotations of generic functions are evaluated within the +annotation scope used for declaring the type parameters, but the +function’s defaults and decorators are not. + +The following example illustrates the scoping rules for these cases, +as well as for additional flavors of type parameters: + + @decorator + def func[T: int, *Ts, **P](*args: *Ts, arg: Callable[P, T] = some_default): + ... + +Except for the lazy evaluation of the "TypeVar" bound, this is +equivalent to: + + DEFAULT_OF_arg = some_default + + annotation-def TYPE_PARAMS_OF_func(): + + annotation-def BOUND_OF_T(): + return int + # In reality, BOUND_OF_T() is evaluated only on demand. + T = typing.TypeVar("T", bound=BOUND_OF_T()) + + Ts = typing.TypeVarTuple("Ts") + P = typing.ParamSpec("P") + + def func(*args: *Ts, arg: Callable[P, T] = DEFAULT_OF_arg): + ... + + func.__type_params__ = (T, Ts, P) + return func + func = decorator(TYPE_PARAMS_OF_func()) + +The capitalized names like "DEFAULT_OF_arg" are not actually bound at +runtime. + + +Generic classes +--------------- + +Generic classes are declared as follows: + + class Bag[T]: ... + +This syntax is equivalent to: + + annotation-def TYPE_PARAMS_OF_Bag(): + T = typing.TypeVar("T") + class Bag(typing.Generic[T]): + __type_params__ = (T,) + ... + return Bag + Bag = TYPE_PARAMS_OF_Bag() + +Here again "annotation-def" (not a real keyword) indicates an +annotation scope, and the name "TYPE_PARAMS_OF_Bag" is not actually +bound at runtime. + +Generic classes implicitly inherit from "typing.Generic". The base +classes and keyword arguments of generic classes are evaluated within +the type scope for the type parameters, and decorators are evaluated +outside that scope. This is illustrated by this example: + + @decorator + class Bag(Base[T], arg=T): ... + +This is equivalent to: + + annotation-def TYPE_PARAMS_OF_Bag(): + T = typing.TypeVar("T") + class Bag(Base[T], typing.Generic[T], arg=T): + __type_params__ = (T,) + ... + return Bag + Bag = decorator(TYPE_PARAMS_OF_Bag()) + + +Generic type aliases +-------------------- + +The "type" statement can also be used to create a generic type alias: + + type ListOrSet[T] = list[T] | set[T] + +Except for the lazy evaluation of the value, this is equivalent to: + + annotation-def TYPE_PARAMS_OF_ListOrSet(): + T = typing.TypeVar("T") + + annotation-def VALUE_OF_ListOrSet(): + return list[T] | set[T] + # In reality, the value is lazily evaluated + return typing.TypeAliasType("ListOrSet", VALUE_OF_ListOrSet(), type_params=(T,)) + ListOrSet = TYPE_PARAMS_OF_ListOrSet() + +Here, "annotation-def" (not a real keyword) indicates an annotation +scope. The capitalized names like "TYPE_PARAMS_OF_ListOrSet" are not +actually bound at runtime. + + +Annotations +=========== + +Changed in version 3.14: Annotations are now lazily evaluated by +default. + +Variables and function parameters may carry *annotations*, created by +adding a colon after the name, followed by an expression: + + x: annotation = 1 + def f(param: annotation): ... + +Functions may also carry a return annotation following an arrow: + + def f() -> annotation: ... + +Annotations are conventionally used for *type hints*, but this is not +enforced by the language, and in general annotations may contain +arbitrary expressions. The presence of annotations does not change the +runtime semantics of the code, except if some mechanism is used that +introspects and uses the annotations (such as "dataclasses" or +"functools.singledispatch()"). + +By default, annotations are lazily evaluated in a annotation scope. +This means that they are not evaluated when the code containing the +annotation is evaluated. Instead, the interpreter saves information +that can be used to evaluate the annotation later if requested. The +"annotationlib" module provides tools for evaluating annotations. + +If the future statement "from __future__ import annotations" is +present, all annotations are instead stored as strings: + + >>> from __future__ import annotations + >>> def f(param: annotation): ... + >>> f.__annotations__ + {'param': 'annotation'} + +-[ Footnotes ]- + +[1] The exception is propagated to the invocation stack unless there + is a "finally" clause which happens to raise another exception. + That new exception causes the old one to be lost. + +[2] In pattern matching, a sequence is defined as one of the + following: + + * a class that inherits from "collections.abc.Sequence" + + * a Python class that has been registered as + "collections.abc.Sequence" + + * a builtin class that has its (CPython) "Py_TPFLAGS_SEQUENCE" bit + set + + * a class that inherits from any of the above + + The following standard library classes are sequences: + + * "array.array" + + * "collections.deque" + + * "list" + + * "memoryview" + + * "range" + + * "tuple" + + Note: + + Subject values of type "str", "bytes", and "bytearray" do not + match sequence patterns. + +[3] In pattern matching, a mapping is defined as one of the following: + + * a class that inherits from "collections.abc.Mapping" + + * a Python class that has been registered as + "collections.abc.Mapping" + + * a builtin class that has its (CPython) "Py_TPFLAGS_MAPPING" bit + set + + * a class that inherits from any of the above + + The standard library classes "dict" and "types.MappingProxyType" + are mappings. + +[4] A string literal appearing as the first statement in the function + body is transformed into the function’s "__doc__" attribute and + therefore the function’s *docstring*. + +[5] A string literal appearing as the first statement in the class + body is transformed into the namespace’s "__doc__" item and + therefore the class’s *docstring*. +''', + 'context-managers': r'''With Statement Context Managers +******************************* + +A *context manager* is an object that defines the runtime context to +be established when executing a "with" statement. The context manager +handles the entry into, and the exit from, the desired runtime context +for the execution of the block of code. Context managers are normally +invoked using the "with" statement (described in section The with +statement), but can also be used by directly invoking their methods. + +Typical uses of context managers include saving and restoring various +kinds of global state, locking and unlocking resources, closing opened +files, etc. + +For more information on context managers, see Context Manager Types. +The "object" class itself does not provide the context manager +methods. + +object.__enter__(self) + + Enter the runtime context related to this object. The "with" + statement will bind this method’s return value to the target(s) + specified in the "as" clause of the statement, if any. + +object.__exit__(self, exc_type, exc_value, traceback) + + Exit the runtime context related to this object. The parameters + describe the exception that caused the context to be exited. If the + context was exited without an exception, all three arguments will + be "None". + + If an exception is supplied, and the method wishes to suppress the + exception (i.e., prevent it from being propagated), it should + return a true value. Otherwise, the exception will be processed + normally upon exit from this method. + + Note that "__exit__()" methods should not reraise the passed-in + exception; this is the caller’s responsibility. + +See also: + + **PEP 343** - The “with” statement + The specification, background, and examples for the Python "with" + statement. +''', + 'continue': r'''The "continue" statement +************************ + + continue_stmt ::= "continue" + +"continue" may only occur syntactically nested in a "for" or "while" +loop, but not nested in a function or class definition within that +loop. It continues with the next cycle of the nearest enclosing loop. + +When "continue" passes control out of a "try" statement with a +"finally" clause, that "finally" clause is executed before really +starting the next loop cycle. +''', + 'conversions': r'''Arithmetic conversions +********************** + +When a description of an arithmetic operator below uses the phrase +“the numeric arguments are converted to a common real type”, this +means that the operator implementation for built-in types works as +follows: + +* If both arguments are complex numbers, no conversion is performed; + +* if either argument is a complex or a floating-point number, the + other is converted to a floating-point number; + +* otherwise, both must be integers and no conversion is necessary. + +Some additional rules apply for certain operators (e.g., a string as a +left argument to the ‘%’ operator). Extensions must define their own +conversion behavior. +''', + 'customization': r'''Basic customization +******************* + +object.__new__(cls[, ...]) + + Called to create a new instance of class *cls*. "__new__()" is a + static method (special-cased so you need not declare it as such) + that takes the class of which an instance was requested as its + first argument. The remaining arguments are those passed to the + object constructor expression (the call to the class). The return + value of "__new__()" should be the new object instance (usually an + instance of *cls*). + + Typical implementations create a new instance of the class by + invoking the superclass’s "__new__()" method using + "super().__new__(cls[, ...])" with appropriate arguments and then + modifying the newly created instance as necessary before returning + it. + + If "__new__()" is invoked during object construction and it returns + an instance of *cls*, then the new instance’s "__init__()" method + will be invoked like "__init__(self[, ...])", where *self* is the + new instance and the remaining arguments are the same as were + passed to the object constructor. + + If "__new__()" does not return an instance of *cls*, then the new + instance’s "__init__()" method will not be invoked. + + "__new__()" is intended mainly to allow subclasses of immutable + types (like int, str, or tuple) to customize instance creation. It + is also commonly overridden in custom metaclasses in order to + customize class creation. + +object.__init__(self[, ...]) + + Called after the instance has been created (by "__new__()"), but + before it is returned to the caller. The arguments are those + passed to the class constructor expression. If a base class has an + "__init__()" method, the derived class’s "__init__()" method, if + any, must explicitly call it to ensure proper initialization of the + base class part of the instance; for example: + "super().__init__([args...])". + + Because "__new__()" and "__init__()" work together in constructing + objects ("__new__()" to create it, and "__init__()" to customize + it), no non-"None" value may be returned by "__init__()"; doing so + will cause a "TypeError" to be raised at runtime. + +object.__del__(self) + + Called when the instance is about to be destroyed. This is also + called a finalizer or (improperly) a destructor. If a base class + has a "__del__()" method, the derived class’s "__del__()" method, + if any, must explicitly call it to ensure proper deletion of the + base class part of the instance. + + It is possible (though not recommended!) for the "__del__()" method + to postpone destruction of the instance by creating a new reference + to it. This is called object *resurrection*. It is + implementation-dependent whether "__del__()" is called a second + time when a resurrected object is about to be destroyed; the + current *CPython* implementation only calls it once. + + It is not guaranteed that "__del__()" methods are called for + objects that still exist when the interpreter exits. + "weakref.finalize" provides a straightforward way to register a + cleanup function to be called when an object is garbage collected. + + Note: + + "del x" doesn’t directly call "x.__del__()" — the former + decrements the reference count for "x" by one, and the latter is + only called when "x"’s reference count reaches zero. + + **CPython implementation detail:** It is possible for a reference + cycle to prevent the reference count of an object from going to + zero. In this case, the cycle will be later detected and deleted + by the *cyclic garbage collector*. A common cause of reference + cycles is when an exception has been caught in a local variable. + The frame’s locals then reference the exception, which references + its own traceback, which references the locals of all frames caught + in the traceback. + + See also: Documentation for the "gc" module. + + Warning: + + Due to the precarious circumstances under which "__del__()" + methods are invoked, exceptions that occur during their execution + are ignored, and a warning is printed to "sys.stderr" instead. + In particular: + + * "__del__()" can be invoked when arbitrary code is being + executed, including from any arbitrary thread. If "__del__()" + needs to take a lock or invoke any other blocking resource, it + may deadlock as the resource may already be taken by the code + that gets interrupted to execute "__del__()". + + * "__del__()" can be executed during interpreter shutdown. As a + consequence, the global variables it needs to access (including + other modules) may already have been deleted or set to "None". + Python guarantees that globals whose name begins with a single + underscore are deleted from their module before other globals + are deleted; if no other references to such globals exist, this + may help in assuring that imported modules are still available + at the time when the "__del__()" method is called. + +object.__repr__(self) + + Called by the "repr()" built-in function to compute the “official” + string representation of an object. If at all possible, this + should look like a valid Python expression that could be used to + recreate an object with the same value (given an appropriate + environment). If this is not possible, a string of the form + "<...some useful description...>" should be returned. The return + value must be a string object. If a class defines "__repr__()" but + not "__str__()", then "__repr__()" is also used when an “informal” + string representation of instances of that class is required. + + This is typically used for debugging, so it is important that the + representation is information-rich and unambiguous. A default + implementation is provided by the "object" class itself. + +object.__str__(self) + + Called by "str(object)", the default "__format__()" implementation, + and the built-in function "print()", to compute the “informal” or + nicely printable string representation of an object. The return + value must be a str object. + + This method differs from "object.__repr__()" in that there is no + expectation that "__str__()" return a valid Python expression: a + more convenient or concise representation can be used. + + The default implementation defined by the built-in type "object" + calls "object.__repr__()". + +object.__bytes__(self) + + Called by bytes to compute a byte-string representation of an + object. This should return a "bytes" object. The "object" class + itself does not provide this method. + +object.__format__(self, format_spec) + + Called by the "format()" built-in function, and by extension, + evaluation of formatted string literals and the "str.format()" + method, to produce a “formatted” string representation of an + object. The *format_spec* argument is a string that contains a + description of the formatting options desired. The interpretation + of the *format_spec* argument is up to the type implementing + "__format__()", however most classes will either delegate + formatting to one of the built-in types, or use a similar + formatting option syntax. + + See Format Specification Mini-Language for a description of the + standard formatting syntax. + + The return value must be a string object. + + The default implementation by the "object" class should be given an + empty *format_spec* string. It delegates to "__str__()". + + Changed in version 3.4: The __format__ method of "object" itself + raises a "TypeError" if passed any non-empty string. + + Changed in version 3.7: "object.__format__(x, '')" is now + equivalent to "str(x)" rather than "format(str(x), '')". + +object.__lt__(self, other) +object.__le__(self, other) +object.__eq__(self, other) +object.__ne__(self, other) +object.__gt__(self, other) +object.__ge__(self, other) + + These are the so-called “rich comparison” methods. The + correspondence between operator symbols and method names is as + follows: "x<y" calls "x.__lt__(y)", "x<=y" calls "x.__le__(y)", + "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", "x>y" calls + "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)". + + A rich comparison method may return the singleton "NotImplemented" + if it does not implement the operation for a given pair of + arguments. By convention, "False" and "True" are returned for a + successful comparison. However, these methods can return any value, + so if the comparison operator is used in a Boolean context (e.g., + in the condition of an "if" statement), Python will call "bool()" + on the value to determine if the result is true or false. + + By default, "object" implements "__eq__()" by using "is", returning + "NotImplemented" in the case of a false comparison: "True if x is y + else NotImplemented". For "__ne__()", by default it delegates to + "__eq__()" and inverts the result unless it is "NotImplemented". + There are no other implied relationships among the comparison + operators or default implementations; for example, the truth of + "(x<y or x==y)" does not imply "x<=y". To automatically generate + ordering operations from a single root operation, see + "functools.total_ordering()". + + By default, the "object" class provides implementations consistent + with Value comparisons: equality compares according to object + identity, and order comparisons raise "TypeError". Each default + method may generate these results directly, but may also return + "NotImplemented". + + See the paragraph on "__hash__()" for some important notes on + creating *hashable* objects which support custom comparison + operations and are usable as dictionary keys. + + There are no swapped-argument versions of these methods (to be used + when the left argument does not support the operation but the right + argument does); rather, "__lt__()" and "__gt__()" are each other’s + reflection, "__le__()" and "__ge__()" are each other’s reflection, + and "__eq__()" and "__ne__()" are their own reflection. If the + operands are of different types, and the right operand’s type is a + direct or indirect subclass of the left operand’s type, the + reflected method of the right operand has priority, otherwise the + left operand’s method has priority. Virtual subclassing is not + considered. + + When no appropriate method returns any value other than + "NotImplemented", the "==" and "!=" operators will fall back to + "is" and "is not", respectively. + +object.__hash__(self) + + Called by built-in function "hash()" and for operations on members + of hashed collections including "set", "frozenset", and "dict". + The "__hash__()" method should return an integer. The only required + property is that objects which compare equal have the same hash + value; it is advised to mix together the hash values of the + components of the object that also play a part in comparison of + objects by packing them into a tuple and hashing the tuple. + Example: + + def __hash__(self): + return hash((self.name, self.nick, self.color)) + + Note: + + "hash()" truncates the value returned from an object’s custom + "__hash__()" method to the size of a "Py_ssize_t". This is + typically 8 bytes on 64-bit builds and 4 bytes on 32-bit builds. + If an object’s "__hash__()" must interoperate on builds of + different bit sizes, be sure to check the width on all supported + builds. An easy way to do this is with "python -c "import sys; + print(sys.hash_info.width)"". + + If a class does not define an "__eq__()" method it should not + define a "__hash__()" operation either; if it defines "__eq__()" + but not "__hash__()", its instances will not be usable as items in + hashable collections. If a class defines mutable objects and + implements an "__eq__()" method, it should not implement + "__hash__()", since the implementation of *hashable* collections + requires that a key’s hash value is immutable (if the object’s hash + value changes, it will be in the wrong hash bucket). + + User-defined classes have "__eq__()" and "__hash__()" methods by + default (inherited from the "object" class); with them, all objects + compare unequal (except with themselves) and "x.__hash__()" returns + an appropriate value such that "x == y" implies both that "x is y" + and "hash(x) == hash(y)". + + A class that overrides "__eq__()" and does not define "__hash__()" + will have its "__hash__()" implicitly set to "None". When the + "__hash__()" method of a class is "None", instances of the class + will raise an appropriate "TypeError" when a program attempts to + retrieve their hash value, and will also be correctly identified as + unhashable when checking "isinstance(obj, + collections.abc.Hashable)". + + If a class that overrides "__eq__()" needs to retain the + implementation of "__hash__()" from a parent class, the interpreter + must be told this explicitly by setting "__hash__ = + <ParentClass>.__hash__". + + If a class that does not override "__eq__()" wishes to suppress + hash support, it should include "__hash__ = None" in the class + definition. A class which defines its own "__hash__()" that + explicitly raises a "TypeError" would be incorrectly identified as + hashable by an "isinstance(obj, collections.abc.Hashable)" call. + + Note: + + By default, the "__hash__()" values of str and bytes objects are + “salted” with an unpredictable random value. Although they + remain constant within an individual Python process, they are not + predictable between repeated invocations of Python.This is + intended to provide protection against a denial-of-service caused + by carefully chosen inputs that exploit the worst case + performance of a dict insertion, *O*(*n*^2) complexity. See + http://ocert.org/advisories/ocert-2011-003.html for + details.Changing hash values affects the iteration order of sets. + Python has never made guarantees about this ordering (and it + typically varies between 32-bit and 64-bit builds).See also + "PYTHONHASHSEED". + + Changed in version 3.3: Hash randomization is enabled by default. + +object.__bool__(self) + + Called to implement truth value testing and the built-in operation + "bool()"; should return "False" or "True". When this method is not + defined, "__len__()" is called, if it is defined, and the object is + considered true if its result is nonzero. If a class defines + neither "__len__()" nor "__bool__()" (which is true of the "object" + class itself), all its instances are considered true. +''', + 'debugger': r'''"pdb" — The Python Debugger +*************************** + +**Source code:** Lib/pdb.py + +====================================================================== + +The module "pdb" defines an interactive source code debugger for +Python programs. It supports setting (conditional) breakpoints and +single stepping at the source line level, inspection of stack frames, +source code listing, and evaluation of arbitrary Python code in the +context of any stack frame. It also supports post-mortem debugging +and can be called under program control. + +The debugger is extensible – it is actually defined as the class +"Pdb". This is currently undocumented but easily understood by reading +the source. The extension interface uses the modules "bdb" and "cmd". + +See also: + + Module "faulthandler" + Used to dump Python tracebacks explicitly, on a fault, after a + timeout, or on a user signal. + + Module "traceback" + Standard interface to extract, format and print stack traces of + Python programs. + +The typical usage to break into the debugger is to insert: + + import pdb; pdb.set_trace() + +Or: + + breakpoint() + +at the location you want to break into the debugger, and then run the +program. You can then step through the code following this statement, +and continue running without the debugger using the "continue" +command. + +Changed in version 3.7: The built-in "breakpoint()", when called with +defaults, can be used instead of "import pdb; pdb.set_trace()". + + def double(x): + breakpoint() + return x * 2 + val = 3 + print(f"{val} * 2 is {double(val)}") + +The debugger’s prompt is "(Pdb)", which is the indicator that you are +in debug mode: + + > ...(2)double() + -> breakpoint() + (Pdb) p x + 3 + (Pdb) continue + 3 * 2 is 6 + +Changed in version 3.3: Tab-completion via the "readline" module is +available for commands and command arguments, e.g. the current global +and local names are offered as arguments of the "p" command. + +You can also invoke "pdb" from the command line to debug other +scripts. For example: + + python -m pdb myscript.py + +When invoked as a module, pdb will automatically enter post-mortem +debugging if the program being debugged exits abnormally. After post- +mortem debugging (or after normal exit of the program), pdb will +restart the program. Automatic restarting preserves pdb’s state (such +as breakpoints) and in most cases is more useful than quitting the +debugger upon program’s exit. + +Changed in version 3.2: Added the "-c" option to execute commands as +if given in a ".pdbrc" file; see Debugger Commands. + +Changed in version 3.7: Added the "-m" option to execute modules +similar to the way "python -m" does. As with a script, the debugger +will pause execution just before the first line of the module. + +Typical usage to execute a statement under control of the debugger is: + + >>> import pdb + >>> def f(x): + ... print(1 / x) + >>> pdb.run("f(2)") + > <string>(1)<module>() + (Pdb) continue + 0.5 + >>> + +The typical usage to inspect a crashed program is: + + >>> import pdb + >>> def f(x): + ... print(1 / x) + ... + >>> f(0) + Traceback (most recent call last): + File "<stdin>", line 1, in <module> + File "<stdin>", line 2, in f + ZeroDivisionError: division by zero + >>> pdb.pm() + > <stdin>(2)f() + (Pdb) p x + 0 + (Pdb) + +Changed in version 3.13: The implementation of **PEP 667** means that +name assignments made via "pdb" will immediately affect the active +scope, even when running inside an *optimized scope*. + +The module defines the following functions; each enters the debugger +in a slightly different way: + +pdb.run(statement, globals=None, locals=None) + + Execute the *statement* (given as a string or a code object) under + debugger control. The debugger prompt appears before any code is + executed; you can set breakpoints and type "continue", or you can + step through the statement using "step" or "next" (all these + commands are explained below). The optional *globals* and *locals* + arguments specify the environment in which the code is executed; by + default the dictionary of the module "__main__" is used. (See the + explanation of the built-in "exec()" or "eval()" functions.) + +pdb.runeval(expression, globals=None, locals=None) + + Evaluate the *expression* (given as a string or a code object) + under debugger control. When "runeval()" returns, it returns the + value of the *expression*. Otherwise this function is similar to + "run()". + +pdb.runcall(function, *args, **kwds) + + Call the *function* (a function or method object, not a string) + with the given arguments. When "runcall()" returns, it returns + whatever the function call returned. The debugger prompt appears + as soon as the function is entered. + +pdb.set_trace(*, header=None, commands=None) + + Enter the debugger at the calling stack frame. This is useful to + hard-code a breakpoint at a given point in a program, even if the + code is not otherwise being debugged (e.g. when an assertion + fails). If given, *header* is printed to the console just before + debugging begins. The *commands* argument, if given, is a list of + commands to execute when the debugger starts. + + Changed in version 3.7: The keyword-only argument *header*. + + Changed in version 3.13: "set_trace()" will enter the debugger + immediately, rather than on the next line of code to be executed. + + Added in version 3.14: The *commands* argument. + +pdb.post_mortem(t=None) + + Enter post-mortem debugging of the given exception or traceback + object. If no value is given, it uses the exception that is + currently being handled, or raises "ValueError" if there isn’t one. + + Changed in version 3.13: Support for exception objects was added. + +pdb.pm() + + Enter post-mortem debugging of the exception found in + "sys.last_exc". + +The "run*" functions and "set_trace()" are aliases for instantiating +the "Pdb" class and calling the method of the same name. If you want +to access further features, you have to do this yourself: + +class pdb.Pdb(completekey='tab', stdin=None, stdout=None, skip=None, nosigint=False, readrc=True, mode=None) + + "Pdb" is the debugger class. + + The *completekey*, *stdin* and *stdout* arguments are passed to the + underlying "cmd.Cmd" class; see the description there. + + The *skip* argument, if given, must be an iterable of glob-style + module name patterns. The debugger will not step into frames that + originate in a module that matches one of these patterns. [1] + + By default, Pdb sets a handler for the SIGINT signal (which is sent + when the user presses "Ctrl"-"C" on the console) when you give a + "continue" command. This allows you to break into the debugger + again by pressing "Ctrl"-"C". If you want Pdb not to touch the + SIGINT handler, set *nosigint* to true. + + The *readrc* argument defaults to true and controls whether Pdb + will load .pdbrc files from the filesystem. + + The *mode* argument specifies how the debugger was invoked. It + impacts the workings of some debugger commands. Valid values are + "'inline'" (used by the breakpoint() builtin), "'cli'" (used by the + command line invocation) or "None" (for backwards compatible + behaviour, as before the *mode* argument was added). + + Example call to enable tracing with *skip*: + + import pdb; pdb.Pdb(skip=['django.*']).set_trace() + + Raises an auditing event "pdb.Pdb" with no arguments. + + Changed in version 3.1: Added the *skip* parameter. + + Changed in version 3.2: Added the *nosigint* parameter. Previously, + a SIGINT handler was never set by Pdb. + + Changed in version 3.6: The *readrc* argument. + + Added in version 3.14: Added the *mode* argument. + + run(statement, globals=None, locals=None) + runeval(expression, globals=None, locals=None) + runcall(function, *args, **kwds) + set_trace() + + See the documentation for the functions explained above. + + +Debugger Commands +================= + +The commands recognized by the debugger are listed below. Most +commands can be abbreviated to one or two letters as indicated; e.g. +"h(elp)" means that either "h" or "help" can be used to enter the help +command (but not "he" or "hel", nor "H" or "Help" or "HELP"). +Arguments to commands must be separated by whitespace (spaces or +tabs). Optional arguments are enclosed in square brackets ("[]") in +the command syntax; the square brackets must not be typed. +Alternatives in the command syntax are separated by a vertical bar +("|"). + +Entering a blank line repeats the last command entered. Exception: if +the last command was a "list" command, the next 11 lines are listed. + +Commands that the debugger doesn’t recognize are assumed to be Python +statements and are executed in the context of the program being +debugged. Python statements can also be prefixed with an exclamation +point ("!"). This is a powerful way to inspect the program being +debugged; it is even possible to change a variable or call a function. +When an exception occurs in such a statement, the exception name is +printed but the debugger’s state is not changed. + +Changed in version 3.13: Expressions/Statements whose prefix is a pdb +command are now correctly identified and executed. + +The debugger supports aliases. Aliases can have parameters which +allows one a certain level of adaptability to the context under +examination. + +Multiple commands may be entered on a single line, separated by ";;". +(A single ";" is not used as it is the separator for multiple commands +in a line that is passed to the Python parser.) No intelligence is +applied to separating the commands; the input is split at the first +";;" pair, even if it is in the middle of a quoted string. A +workaround for strings with double semicolons is to use implicit +string concatenation "';'';'" or "";"";"". + +To set a temporary global variable, use a *convenience variable*. A +*convenience variable* is a variable whose name starts with "$". For +example, "$foo = 1" sets a global variable "$foo" which you can use in +the debugger session. The *convenience variables* are cleared when +the program resumes execution so it’s less likely to interfere with +your program compared to using normal variables like "foo = 1". + +There are three preset *convenience variables*: + +* "$_frame": the current frame you are debugging + +* "$_retval": the return value if the frame is returning + +* "$_exception": the exception if the frame is raising an exception + +Added in version 3.12: Added the *convenience variable* feature. + +If a file ".pdbrc" exists in the user’s home directory or in the +current directory, it is read with "'utf-8'" encoding and executed as +if it had been typed at the debugger prompt, with the exception that +empty lines and lines starting with "#" are ignored. This is +particularly useful for aliases. If both files exist, the one in the +home directory is read first and aliases defined there can be +overridden by the local file. + +Changed in version 3.2: ".pdbrc" can now contain commands that +continue debugging, such as "continue" or "next". Previously, these +commands had no effect. + +Changed in version 3.11: ".pdbrc" is now read with "'utf-8'" encoding. +Previously, it was read with the system locale encoding. + +h(elp) [command] + + Without argument, print the list of available commands. With a + *command* as argument, print help about that command. "help pdb" + displays the full documentation (the docstring of the "pdb" + module). Since the *command* argument must be an identifier, "help + exec" must be entered to get help on the "!" command. + +w(here) [count] + + Print a stack trace, with the most recent frame at the bottom. if + *count* is 0, print the current frame entry. If *count* is + negative, print the least recent - *count* frames. If *count* is + positive, print the most recent *count* frames. An arrow (">") + indicates the current frame, which determines the context of most + commands. + + Changed in version 3.14: *count* argument is added. + +d(own) [count] + + Move the current frame *count* (default one) levels down in the + stack trace (to a newer frame). + +u(p) [count] + + Move the current frame *count* (default one) levels up in the stack + trace (to an older frame). + +b(reak) [([filename:]lineno | function) [, condition]] + + With a *lineno* argument, set a break at line *lineno* in the + current file. The line number may be prefixed with a *filename* and + a colon, to specify a breakpoint in another file (possibly one that + hasn’t been loaded yet). The file is searched on "sys.path". + Acceptable forms of *filename* are "/abspath/to/file.py", + "relpath/file.py", "module" and "package.module". + + With a *function* argument, set a break at the first executable + statement within that function. *function* can be any expression + that evaluates to a function in the current namespace. + + If a second argument is present, it is an expression which must + evaluate to true before the breakpoint is honored. + + Without argument, list all breaks, including for each breakpoint, + the number of times that breakpoint has been hit, the current + ignore count, and the associated condition if any. + + Each breakpoint is assigned a number to which all the other + breakpoint commands refer. + +tbreak [([filename:]lineno | function) [, condition]] + + Temporary breakpoint, which is removed automatically when it is + first hit. The arguments are the same as for "break". + +cl(ear) [filename:lineno | bpnumber ...] + + With a *filename:lineno* argument, clear all the breakpoints at + this line. With a space separated list of breakpoint numbers, clear + those breakpoints. Without argument, clear all breaks (but first + ask confirmation). + +disable bpnumber [bpnumber ...] + + Disable the breakpoints given as a space separated list of + breakpoint numbers. Disabling a breakpoint means it cannot cause + the program to stop execution, but unlike clearing a breakpoint, it + remains in the list of breakpoints and can be (re-)enabled. + +enable bpnumber [bpnumber ...] + + Enable the breakpoints specified. + +ignore bpnumber [count] + + Set the ignore count for the given breakpoint number. If *count* + is omitted, the ignore count is set to 0. A breakpoint becomes + active when the ignore count is zero. When non-zero, the *count* + is decremented each time the breakpoint is reached and the + breakpoint is not disabled and any associated condition evaluates + to true. + +condition bpnumber [condition] + + Set a new *condition* for the breakpoint, an expression which must + evaluate to true before the breakpoint is honored. If *condition* + is absent, any existing condition is removed; i.e., the breakpoint + is made unconditional. + +commands [bpnumber] + + Specify a list of commands for breakpoint number *bpnumber*. The + commands themselves appear on the following lines. Type a line + containing just "end" to terminate the commands. An example: + + (Pdb) commands 1 + (com) p some_variable + (com) end + (Pdb) + + To remove all commands from a breakpoint, type "commands" and + follow it immediately with "end"; that is, give no commands. + + With no *bpnumber* argument, "commands" refers to the last + breakpoint set. + + You can use breakpoint commands to start your program up again. + Simply use the "continue" command, or "step", or any other command + that resumes execution. + + Specifying any command resuming execution (currently "continue", + "step", "next", "return", "until", "jump", "quit" and their + abbreviations) terminates the command list (as if that command was + immediately followed by end). This is because any time you resume + execution (even with a simple next or step), you may encounter + another breakpoint—which could have its own command list, leading + to ambiguities about which list to execute. + + If the list of commands contains the "silent" command, or a command + that resumes execution, then the breakpoint message containing + information about the frame is not displayed. + + Changed in version 3.14: Frame information will not be displayed if + a command that resumes execution is present in the command list. + +s(tep) + + Execute the current line, stop at the first possible occasion + (either in a function that is called or on the next line in the + current function). + +n(ext) + + Continue execution until the next line in the current function is + reached or it returns. (The difference between "next" and "step" + is that "step" stops inside a called function, while "next" + executes called functions at (nearly) full speed, only stopping at + the next line in the current function.) + +unt(il) [lineno] + + Without argument, continue execution until the line with a number + greater than the current one is reached. + + With *lineno*, continue execution until a line with a number + greater or equal to *lineno* is reached. In both cases, also stop + when the current frame returns. + + Changed in version 3.2: Allow giving an explicit line number. + +r(eturn) + + Continue execution until the current function returns. + +c(ont(inue)) + + Continue execution, only stop when a breakpoint is encountered. + +j(ump) lineno + + Set the next line that will be executed. Only available in the + bottom-most frame. This lets you jump back and execute code again, + or jump forward to skip code that you don’t want to run. + + It should be noted that not all jumps are allowed – for instance it + is not possible to jump into the middle of a "for" loop or out of a + "finally" clause. + +l(ist) [first[, last]] + + List source code for the current file. Without arguments, list 11 + lines around the current line or continue the previous listing. + With "." as argument, list 11 lines around the current line. With + one argument, list 11 lines around at that line. With two + arguments, list the given range; if the second argument is less + than the first, it is interpreted as a count. + + The current line in the current frame is indicated by "->". If an + exception is being debugged, the line where the exception was + originally raised or propagated is indicated by ">>", if it differs + from the current line. + + Changed in version 3.2: Added the ">>" marker. + +ll | longlist + + List all source code for the current function or frame. + Interesting lines are marked as for "list". + + Added in version 3.2. + +a(rgs) + + Print the arguments of the current function and their current + values. + +p expression + + Evaluate *expression* in the current context and print its value. + + Note: + + "print()" can also be used, but is not a debugger command — this + executes the Python "print()" function. + +pp expression + + Like the "p" command, except the value of *expression* is pretty- + printed using the "pprint" module. + +whatis expression + + Print the type of *expression*. + +source expression + + Try to get source code of *expression* and display it. + + Added in version 3.2. + +display [expression] + + Display the value of *expression* if it changed, each time + execution stops in the current frame. + + Without *expression*, list all display expressions for the current + frame. + + Note: + + Display evaluates *expression* and compares to the result of the + previous evaluation of *expression*, so when the result is + mutable, display may not be able to pick up the changes. + + Example: + + lst = [] + breakpoint() + pass + lst.append(1) + print(lst) + + Display won’t realize "lst" has been changed because the result of + evaluation is modified in place by "lst.append(1)" before being + compared: + + > example.py(3)<module>() + -> pass + (Pdb) display lst + display lst: [] + (Pdb) n + > example.py(4)<module>() + -> lst.append(1) + (Pdb) n + > example.py(5)<module>() + -> print(lst) + (Pdb) + + You can do some tricks with copy mechanism to make it work: + + > example.py(3)<module>() + -> pass + (Pdb) display lst[:] + display lst[:]: [] + (Pdb) n + > example.py(4)<module>() + -> lst.append(1) + (Pdb) n + > example.py(5)<module>() + -> print(lst) + display lst[:]: [1] [old: []] + (Pdb) + + Added in version 3.2. + +undisplay [expression] + + Do not display *expression* anymore in the current frame. Without + *expression*, clear all display expressions for the current frame. + + Added in version 3.2. + +interact + + Start an interactive interpreter (using the "code" module) in a new + global namespace initialised from the local and global namespaces + for the current scope. Use "exit()" or "quit()" to exit the + interpreter and return to the debugger. + + Note: + + As "interact" creates a new dedicated namespace for code + execution, assignments to variables will not affect the original + namespaces. However, modifications to any referenced mutable + objects will be reflected in the original namespaces as usual. + + Added in version 3.2. + + Changed in version 3.13: "exit()" and "quit()" can be used to exit + the "interact" command. + + Changed in version 3.13: "interact" directs its output to the + debugger’s output channel rather than "sys.stderr". + +alias [name [command]] + + Create an alias called *name* that executes *command*. The + *command* must *not* be enclosed in quotes. Replaceable parameters + can be indicated by "%1", "%2", … and "%9", while "%*" is replaced + by all the parameters. If *command* is omitted, the current alias + for *name* is shown. If no arguments are given, all aliases are + listed. + + Aliases may be nested and can contain anything that can be legally + typed at the pdb prompt. Note that internal pdb commands *can* be + overridden by aliases. Such a command is then hidden until the + alias is removed. Aliasing is recursively applied to the first + word of the command line; all other words in the line are left + alone. + + As an example, here are two useful aliases (especially when placed + in the ".pdbrc" file): + + # Print instance variables (usage "pi classInst") + alias pi for k in %1.__dict__.keys(): print(f"%1.{k} = {%1.__dict__[k]}") + # Print instance variables in self + alias ps pi self + +unalias name + + Delete the specified alias *name*. + +! statement + + Execute the (one-line) *statement* in the context of the current + stack frame. The exclamation point can be omitted unless the first + word of the statement resembles a debugger command, e.g.: + + (Pdb) ! n=42 + (Pdb) + + To set a global variable, you can prefix the assignment command + with a "global" statement on the same line, e.g.: + + (Pdb) global list_options; list_options = ['-l'] + (Pdb) + +run [args ...] +restart [args ...] + + Restart the debugged Python program. If *args* is supplied, it is + split with "shlex" and the result is used as the new "sys.argv". + History, breakpoints, actions and debugger options are preserved. + "restart" is an alias for "run". + + Changed in version 3.14: "run" and "restart" commands are disabled + when the debugger is invoked in "'inline'" mode. + +q(uit) + + Quit from the debugger. The program being executed is aborted. + +debug code + + Enter a recursive debugger that steps through *code* (which is an + arbitrary expression or statement to be executed in the current + environment). + +retval + + Print the return value for the last return of the current function. + +exceptions [excnumber] + + List or jump between chained exceptions. + + When using "pdb.pm()" or "Pdb.post_mortem(...)" with a chained + exception instead of a traceback, it allows the user to move + between the chained exceptions using "exceptions" command to list + exceptions, and "exception <number>" to switch to that exception. + + Example: + + def out(): + try: + middle() + except Exception as e: + raise ValueError("reraise middle() error") from e + + def middle(): + try: + return inner(0) + except Exception as e: + raise ValueError("Middle fail") + + def inner(x): + 1 / x + + out() + + calling "pdb.pm()" will allow to move between exceptions: + + > example.py(5)out() + -> raise ValueError("reraise middle() error") from e + + (Pdb) exceptions + 0 ZeroDivisionError('division by zero') + 1 ValueError('Middle fail') + > 2 ValueError('reraise middle() error') + + (Pdb) exceptions 0 + > example.py(16)inner() + -> 1 / x + + (Pdb) up + > example.py(10)middle() + -> return inner(0) + + Added in version 3.13. + +-[ Footnotes ]- + +[1] Whether a frame is considered to originate in a certain module is + determined by the "__name__" in the frame globals. +''', + 'del': r'''The "del" statement +******************* + + del_stmt ::= "del" target_list + +Deletion is recursively defined very similar to the way assignment is +defined. Rather than spelling it out in full details, here are some +hints. + +Deletion of a target list recursively deletes each target, from left +to right. + +Deletion of a name removes the binding of that name from the local or +global namespace, depending on whether the name occurs in a "global" +statement in the same code block. If the name is unbound, a +"NameError" exception will be raised. + +Deletion of attribute references, subscriptions and slicings is passed +to the primary object involved; deletion of a slicing is in general +equivalent to assignment of an empty slice of the right type (but even +this is determined by the sliced object). + +Changed in version 3.2: Previously it was illegal to delete a name +from the local namespace if it occurs as a free variable in a nested +block. +''', + 'dict': r'''Dictionary displays +******************* + +A dictionary display is a possibly empty series of dict items +(key/value pairs) enclosed in curly braces: + + dict_display ::= "{" [dict_item_list | dict_comprehension] "}" + dict_item_list ::= dict_item ("," dict_item)* [","] + dict_item ::= expression ":" expression | "**" or_expr + dict_comprehension ::= expression ":" expression comp_for + +A dictionary display yields a new dictionary object. + +If a comma-separated sequence of dict items is given, they are +evaluated from left to right to define the entries of the dictionary: +each key object is used as a key into the dictionary to store the +corresponding value. This means that you can specify the same key +multiple times in the dict item list, and the final dictionary’s value +for that key will be the last one given. + +A double asterisk "**" denotes *dictionary unpacking*. Its operand +must be a *mapping*. Each mapping item is added to the new +dictionary. Later values replace values already set by earlier dict +items and earlier dictionary unpackings. + +Added in version 3.5: Unpacking into dictionary displays, originally +proposed by **PEP 448**. + +A dict comprehension, in contrast to list and set comprehensions, +needs two expressions separated with a colon followed by the usual +“for” and “if” clauses. When the comprehension is run, the resulting +key and value elements are inserted in the new dictionary in the order +they are produced. + +Restrictions on the types of the key values are listed earlier in +section The standard type hierarchy. (To summarize, the key type +should be *hashable*, which excludes all mutable objects.) Clashes +between duplicate keys are not detected; the last value (textually +rightmost in the display) stored for a given key value prevails. + +Changed in version 3.8: Prior to Python 3.8, in dict comprehensions, +the evaluation order of key and value was not well-defined. In +CPython, the value was evaluated before the key. Starting with 3.8, +the key is evaluated before the value, as proposed by **PEP 572**. +''', + 'dynamic-features': r'''Interaction with dynamic features +********************************* + +Name resolution of free variables occurs at runtime, not at compile +time. This means that the following code will print 42: + + i = 10 + def f(): + print(i) + i = 42 + f() + +The "eval()" and "exec()" functions do not have access to the full +environment for resolving names. Names may be resolved in the local +and global namespaces of the caller. Free variables are not resolved +in the nearest enclosing namespace, but in the global namespace. [1] +The "exec()" and "eval()" functions have optional arguments to +override the global and local namespace. If only one namespace is +specified, it is used for both. +''', + 'else': r'''The "if" statement +****************** + +The "if" statement is used for conditional execution: + + if_stmt ::= "if" assignment_expression ":" suite + ("elif" assignment_expression ":" suite)* + ["else" ":" suite] + +It selects exactly one of the suites by evaluating the expressions one +by one until one is found to be true (see section Boolean operations +for the definition of true and false); then that suite is executed +(and no other part of the "if" statement is executed or evaluated). +If all expressions are false, the suite of the "else" clause, if +present, is executed. +''', + 'exceptions': r'''Exceptions +********** + +Exceptions are a means of breaking out of the normal flow of control +of a code block in order to handle errors or other exceptional +conditions. An exception is *raised* at the point where the error is +detected; it may be *handled* by the surrounding code block or by any +code block that directly or indirectly invoked the code block where +the error occurred. + +The Python interpreter raises an exception when it detects a run-time +error (such as division by zero). A Python program can also +explicitly raise an exception with the "raise" statement. Exception +handlers are specified with the "try" … "except" statement. The +"finally" clause of such a statement can be used to specify cleanup +code which does not handle the exception, but is executed whether an +exception occurred or not in the preceding code. + +Python uses the “termination” model of error handling: an exception +handler can find out what happened and continue execution at an outer +level, but it cannot repair the cause of the error and retry the +failing operation (except by re-entering the offending piece of code +from the top). + +When an exception is not handled at all, the interpreter terminates +execution of the program, or returns to its interactive main loop. In +either case, it prints a stack traceback, except when the exception is +"SystemExit". + +Exceptions are identified by class instances. The "except" clause is +selected depending on the class of the instance: it must reference the +class of the instance or a *non-virtual base class* thereof. The +instance can be received by the handler and can carry additional +information about the exceptional condition. + +Note: + + Exception messages are not part of the Python API. Their contents + may change from one version of Python to the next without warning + and should not be relied on by code which will run under multiple + versions of the interpreter. + +See also the description of the "try" statement in section The try +statement and "raise" statement in section The raise statement. + +-[ Footnotes ]- + +[1] This limitation occurs because the code that is executed by these + operations is not available at the time the module is compiled. +''', + 'execmodel': r'''Execution model +*************** + + +Structure of a program +====================== + +A Python program is constructed from code blocks. A *block* is a piece +of Python program text that is executed as a unit. The following are +blocks: a module, a function body, and a class definition. Each +command typed interactively is a block. A script file (a file given +as standard input to the interpreter or specified as a command line +argument to the interpreter) is a code block. A script command (a +command specified on the interpreter command line with the "-c" +option) is a code block. A module run as a top level script (as module +"__main__") from the command line using a "-m" argument is also a code +block. The string argument passed to the built-in functions "eval()" +and "exec()" is a code block. + +A code block is executed in an *execution frame*. A frame contains +some administrative information (used for debugging) and determines +where and how execution continues after the code block’s execution has +completed. + + +Naming and binding +================== + + +Binding of names +---------------- + +*Names* refer to objects. Names are introduced by name binding +operations. + +The following constructs bind names: + +* formal parameters to functions, + +* class definitions, + +* function definitions, + +* assignment expressions, + +* targets that are identifiers if occurring in an assignment: + + * "for" loop header, + + * after "as" in a "with" statement, "except" clause, "except*" + clause, or in the as-pattern in structural pattern matching, + + * in a capture pattern in structural pattern matching + +* "import" statements. + +* "type" statements. + +* type parameter lists. + +The "import" statement of the form "from ... import *" binds all names +defined in the imported module, except those beginning with an +underscore. This form may only be used at the module level. + +A target occurring in a "del" statement is also considered bound for +this purpose (though the actual semantics are to unbind the name). + +Each assignment or import statement occurs within a block defined by a +class or function definition or at the module level (the top-level +code block). + +If a name is bound in a block, it is a local variable of that block, +unless declared as "nonlocal" or "global". If a name is bound at the +module level, it is a global variable. (The variables of the module +code block are local and global.) If a variable is used in a code +block but not defined there, it is a *free variable*. + +Each occurrence of a name in the program text refers to the *binding* +of that name established by the following name resolution rules. + + +Resolution of names +------------------- + +A *scope* defines the visibility of a name within a block. If a local +variable is defined in a block, its scope includes that block. If the +definition occurs in a function block, the scope extends to any blocks +contained within the defining one, unless a contained block introduces +a different binding for the name. + +When a name is used in a code block, it is resolved using the nearest +enclosing scope. The set of all such scopes visible to a code block +is called the block’s *environment*. + +When a name is not found at all, a "NameError" exception is raised. If +the current scope is a function scope, and the name refers to a local +variable that has not yet been bound to a value at the point where the +name is used, an "UnboundLocalError" exception is raised. +"UnboundLocalError" is a subclass of "NameError". + +If a name binding operation occurs anywhere within a code block, all +uses of the name within the block are treated as references to the +current block. This can lead to errors when a name is used within a +block before it is bound. This rule is subtle. Python lacks +declarations and allows name binding operations to occur anywhere +within a code block. The local variables of a code block can be +determined by scanning the entire text of the block for name binding +operations. See the FAQ entry on UnboundLocalError for examples. + +If the "global" statement occurs within a block, all uses of the names +specified in the statement refer to the bindings of those names in the +top-level namespace. Names are resolved in the top-level namespace by +searching the global namespace, i.e. the namespace of the module +containing the code block, and the builtins namespace, the namespace +of the module "builtins". The global namespace is searched first. If +the names are not found there, the builtins namespace is searched +next. If the names are also not found in the builtins namespace, new +variables are created in the global namespace. The global statement +must precede all uses of the listed names. + +The "global" statement has the same scope as a name binding operation +in the same block. If the nearest enclosing scope for a free variable +contains a global statement, the free variable is treated as a global. + +The "nonlocal" statement causes corresponding names to refer to +previously bound variables in the nearest enclosing function scope. +"SyntaxError" is raised at compile time if the given name does not +exist in any enclosing function scope. Type parameters cannot be +rebound with the "nonlocal" statement. + +The namespace for a module is automatically created the first time a +module is imported. The main module for a script is always called +"__main__". + +Class definition blocks and arguments to "exec()" and "eval()" are +special in the context of name resolution. A class definition is an +executable statement that may use and define names. These references +follow the normal rules for name resolution with an exception that +unbound local variables are looked up in the global namespace. The +namespace of the class definition becomes the attribute dictionary of +the class. The scope of names defined in a class block is limited to +the class block; it does not extend to the code blocks of methods. +This includes comprehensions and generator expressions, but it does +not include annotation scopes, which have access to their enclosing +class scopes. This means that the following will fail: + + class A: + a = 42 + b = list(a + i for i in range(10)) + +However, the following will succeed: + + class A: + type Alias = Nested + class Nested: pass + + print(A.Alias.__value__) # <type 'A.Nested'> + + +Annotation scopes +----------------- + +*Annotations*, type parameter lists and "type" statements introduce +*annotation scopes*, which behave mostly like function scopes, but +with some exceptions discussed below. + +Annotation scopes are used in the following contexts: + +* *Function annotations*. + +* *Variable annotations*. + +* Type parameter lists for generic type aliases. + +* Type parameter lists for generic functions. A generic function’s + annotations are executed within the annotation scope, but its + defaults and decorators are not. + +* Type parameter lists for generic classes. A generic class’s base + classes and keyword arguments are executed within the annotation + scope, but its decorators are not. + +* The bounds, constraints, and default values for type parameters + (lazily evaluated). + +* The value of type aliases (lazily evaluated). + +Annotation scopes differ from function scopes in the following ways: + +* Annotation scopes have access to their enclosing class namespace. If + an annotation scope is immediately within a class scope, or within + another annotation scope that is immediately within a class scope, + the code in the annotation scope can use names defined in the class + scope as if it were executed directly within the class body. This + contrasts with regular functions defined within classes, which + cannot access names defined in the class scope. + +* Expressions in annotation scopes cannot contain "yield", "yield + from", "await", or ":=" expressions. (These expressions are allowed + in other scopes contained within the annotation scope.) + +* Names defined in annotation scopes cannot be rebound with "nonlocal" + statements in inner scopes. This includes only type parameters, as + no other syntactic elements that can appear within annotation scopes + can introduce new names. + +* While annotation scopes have an internal name, that name is not + reflected in the *qualified name* of objects defined within the + scope. Instead, the "__qualname__" of such objects is as if the + object were defined in the enclosing scope. + +Added in version 3.12: Annotation scopes were introduced in Python +3.12 as part of **PEP 695**. + +Changed in version 3.13: Annotation scopes are also used for type +parameter defaults, as introduced by **PEP 696**. + +Changed in version 3.14: Annotation scopes are now also used for +annotations, as specified in **PEP 649** and **PEP 749**. + + +Lazy evaluation +--------------- + +Most annotation scopes are *lazily evaluated*. This includes +annotations, the values of type aliases created through the "type" +statement, and the bounds, constraints, and default values of type +variables created through the type parameter syntax. This means that +they are not evaluated when the type alias or type variable is +created, or when the object carrying annotations is created. Instead, +they are only evaluated when necessary, for example when the +"__value__" attribute on a type alias is accessed. + +Example: + + >>> type Alias = 1/0 + >>> Alias.__value__ + Traceback (most recent call last): + ... + ZeroDivisionError: division by zero + >>> def func[T: 1/0](): pass + >>> T = func.__type_params__[0] + >>> T.__bound__ + Traceback (most recent call last): + ... + ZeroDivisionError: division by zero + +Here the exception is raised only when the "__value__" attribute of +the type alias or the "__bound__" attribute of the type variable is +accessed. + +This behavior is primarily useful for references to types that have +not yet been defined when the type alias or type variable is created. +For example, lazy evaluation enables creation of mutually recursive +type aliases: + + from typing import Literal + + type SimpleExpr = int | Parenthesized + type Parenthesized = tuple[Literal["("], Expr, Literal[")"]] + type Expr = SimpleExpr | tuple[SimpleExpr, Literal["+", "-"], Expr] + +Lazily evaluated values are evaluated in annotation scope, which means +that names that appear inside the lazily evaluated value are looked up +as if they were used in the immediately enclosing scope. + +Added in version 3.12. + + +Builtins and restricted execution +--------------------------------- + +**CPython implementation detail:** Users should not touch +"__builtins__"; it is strictly an implementation detail. Users +wanting to override values in the builtins namespace should "import" +the "builtins" module and modify its attributes appropriately. + +The builtins namespace associated with the execution of a code block +is actually found by looking up the name "__builtins__" in its global +namespace; this should be a dictionary or a module (in the latter case +the module’s dictionary is used). By default, when in the "__main__" +module, "__builtins__" is the built-in module "builtins"; when in any +other module, "__builtins__" is an alias for the dictionary of the +"builtins" module itself. + + +Interaction with dynamic features +--------------------------------- + +Name resolution of free variables occurs at runtime, not at compile +time. This means that the following code will print 42: + + i = 10 + def f(): + print(i) + i = 42 + f() + +The "eval()" and "exec()" functions do not have access to the full +environment for resolving names. Names may be resolved in the local +and global namespaces of the caller. Free variables are not resolved +in the nearest enclosing namespace, but in the global namespace. [1] +The "exec()" and "eval()" functions have optional arguments to +override the global and local namespace. If only one namespace is +specified, it is used for both. + + +Exceptions +========== + +Exceptions are a means of breaking out of the normal flow of control +of a code block in order to handle errors or other exceptional +conditions. An exception is *raised* at the point where the error is +detected; it may be *handled* by the surrounding code block or by any +code block that directly or indirectly invoked the code block where +the error occurred. + +The Python interpreter raises an exception when it detects a run-time +error (such as division by zero). A Python program can also +explicitly raise an exception with the "raise" statement. Exception +handlers are specified with the "try" … "except" statement. The +"finally" clause of such a statement can be used to specify cleanup +code which does not handle the exception, but is executed whether an +exception occurred or not in the preceding code. + +Python uses the “termination” model of error handling: an exception +handler can find out what happened and continue execution at an outer +level, but it cannot repair the cause of the error and retry the +failing operation (except by re-entering the offending piece of code +from the top). + +When an exception is not handled at all, the interpreter terminates +execution of the program, or returns to its interactive main loop. In +either case, it prints a stack traceback, except when the exception is +"SystemExit". + +Exceptions are identified by class instances. The "except" clause is +selected depending on the class of the instance: it must reference the +class of the instance or a *non-virtual base class* thereof. The +instance can be received by the handler and can carry additional +information about the exceptional condition. + +Note: + + Exception messages are not part of the Python API. Their contents + may change from one version of Python to the next without warning + and should not be relied on by code which will run under multiple + versions of the interpreter. + +See also the description of the "try" statement in section The try +statement and "raise" statement in section The raise statement. + +-[ Footnotes ]- + +[1] This limitation occurs because the code that is executed by these + operations is not available at the time the module is compiled. +''', + 'exprlists': r'''Expression lists +**************** + + starred_expression ::= ["*"] or_expr + flexible_expression ::= assignment_expression | starred_expression + flexible_expression_list ::= flexible_expression ("," flexible_expression)* [","] + starred_expression_list ::= starred_expression ("," starred_expression)* [","] + expression_list ::= expression ("," expression)* [","] + yield_list ::= expression_list | starred_expression "," [starred_expression_list] + +Except when part of a list or set display, an expression list +containing at least one comma yields a tuple. The length of the tuple +is the number of expressions in the list. The expressions are +evaluated from left to right. + +An asterisk "*" denotes *iterable unpacking*. Its operand must be an +*iterable*. The iterable is expanded into a sequence of items, which +are included in the new tuple, list, or set, at the site of the +unpacking. + +Added in version 3.5: Iterable unpacking in expression lists, +originally proposed by **PEP 448**. + +Added in version 3.11: Any item in an expression list may be starred. +See **PEP 646**. + +A trailing comma is required only to create a one-item tuple, such as +"1,"; it is optional in all other cases. A single expression without a +trailing comma doesn’t create a tuple, but rather yields the value of +that expression. (To create an empty tuple, use an empty pair of +parentheses: "()".) +''', + 'floating': r'''Floating-point literals +*********************** + +Floating-point literals are described by the following lexical +definitions: + + floatnumber ::= pointfloat | exponentfloat + pointfloat ::= [digitpart] fraction | digitpart "." + exponentfloat ::= (digitpart | pointfloat) exponent + digitpart ::= digit (["_"] digit)* + fraction ::= "." digitpart + exponent ::= ("e" | "E") ["+" | "-"] digitpart + +Note that the integer and exponent parts are always interpreted using +radix 10. For example, "077e010" is legal, and denotes the same number +as "77e10". The allowed range of floating-point literals is +implementation-dependent. As in integer literals, underscores are +supported for digit grouping. + +Some examples of floating-point literals: + + 3.14 10. .001 1e100 3.14e-10 0e0 3.14_15_93 + +Changed in version 3.6: Underscores are now allowed for grouping +purposes in literals. +''', + 'for': r'''The "for" statement +******************* + +The "for" statement is used to iterate over the elements of a sequence +(such as a string, tuple or list) or other iterable object: + + for_stmt ::= "for" target_list "in" starred_list ":" suite + ["else" ":" suite] + +The "starred_list" expression is evaluated once; it should yield an +*iterable* object. An *iterator* is created for that iterable. The +first item provided by the iterator is then assigned to the target +list using the standard rules for assignments (see Assignment +statements), and the suite is executed. This repeats for each item +provided by the iterator. When the iterator is exhausted, the suite +in the "else" clause, if present, is executed, and the loop +terminates. + +A "break" statement executed in the first suite terminates the loop +without executing the "else" clause’s suite. A "continue" statement +executed in the first suite skips the rest of the suite and continues +with the next item, or with the "else" clause if there is no next +item. + +The for-loop makes assignments to the variables in the target list. +This overwrites all previous assignments to those variables including +those made in the suite of the for-loop: + + for i in range(10): + print(i) + i = 5 # this will not affect the for-loop + # because i will be overwritten with the next + # index in the range + +Names in the target list are not deleted when the loop is finished, +but if the sequence is empty, they will not have been assigned to at +all by the loop. Hint: the built-in type "range()" represents +immutable arithmetic sequences of integers. For instance, iterating +"range(3)" successively yields 0, 1, and then 2. + +Changed in version 3.11: Starred elements are now allowed in the +expression list. +''', + 'formatstrings': r'''Format String Syntax +******************** + +The "str.format()" method and the "Formatter" class share the same +syntax for format strings (although in the case of "Formatter", +subclasses can define their own format string syntax). The syntax is +related to that of formatted string literals, but it is less +sophisticated and, in particular, does not support arbitrary +expressions. + +Format strings contain “replacement fields” surrounded by curly braces +"{}". Anything that is not contained in braces is considered literal +text, which is copied unchanged to the output. If you need to include +a brace character in the literal text, it can be escaped by doubling: +"{{" and "}}". + +The grammar for a replacement field is as follows: + + replacement_field ::= "{" [field_name] ["!" conversion] [":" format_spec] "}" + field_name ::= arg_name ("." attribute_name | "[" element_index "]")* + arg_name ::= [identifier | digit+] + attribute_name ::= identifier + element_index ::= digit+ | index_string + index_string ::= <any source character except "]"> + + conversion ::= "r" | "s" | "a" + format_spec ::= format-spec:format_spec + +In less formal terms, the replacement field can start with a +*field_name* that specifies the object whose value is to be formatted +and inserted into the output instead of the replacement field. The +*field_name* is optionally followed by a *conversion* field, which is +preceded by an exclamation point "'!'", and a *format_spec*, which is +preceded by a colon "':'". These specify a non-default format for the +replacement value. + +See also the Format Specification Mini-Language section. + +The *field_name* itself begins with an *arg_name* that is either a +number or a keyword. If it’s a number, it refers to a positional +argument, and if it’s a keyword, it refers to a named keyword +argument. An *arg_name* is treated as a number if a call to +"str.isdecimal()" on the string would return true. If the numerical +arg_names in a format string are 0, 1, 2, … in sequence, they can all +be omitted (not just some) and the numbers 0, 1, 2, … will be +automatically inserted in that order. Because *arg_name* is not quote- +delimited, it is not possible to specify arbitrary dictionary keys +(e.g., the strings "'10'" or "':-]'") within a format string. The +*arg_name* can be followed by any number of index or attribute +expressions. An expression of the form "'.name'" selects the named +attribute using "getattr()", while an expression of the form +"'[index]'" does an index lookup using "__getitem__()". + +Changed in version 3.1: The positional argument specifiers can be +omitted for "str.format()", so "'{} {}'.format(a, b)" is equivalent to +"'{0} {1}'.format(a, b)". + +Changed in version 3.4: The positional argument specifiers can be +omitted for "Formatter". + +Some simple format string examples: + + "First, thou shalt count to {0}" # References first positional argument + "Bring me a {}" # Implicitly references the first positional argument + "From {} to {}" # Same as "From {0} to {1}" + "My quest is {name}" # References keyword argument 'name' + "Weight in tons {0.weight}" # 'weight' attribute of first positional arg + "Units destroyed: {players[0]}" # First element of keyword argument 'players'. + +The *conversion* field causes a type coercion before formatting. +Normally, the job of formatting a value is done by the "__format__()" +method of the value itself. However, in some cases it is desirable to +force a type to be formatted as a string, overriding its own +definition of formatting. By converting the value to a string before +calling "__format__()", the normal formatting logic is bypassed. + +Three conversion flags are currently supported: "'!s'" which calls +"str()" on the value, "'!r'" which calls "repr()" and "'!a'" which +calls "ascii()". + +Some examples: + + "Harold's a clever {0!s}" # Calls str() on the argument first + "Bring out the holy {name!r}" # Calls repr() on the argument first + "More {!a}" # Calls ascii() on the argument first + +The *format_spec* field contains a specification of how the value +should be presented, including such details as field width, alignment, +padding, decimal precision and so on. Each value type can define its +own “formatting mini-language” or interpretation of the *format_spec*. + +Most built-in types support a common formatting mini-language, which +is described in the next section. + +A *format_spec* field can also include nested replacement fields +within it. These nested replacement fields may contain a field name, +conversion flag and format specification, but deeper nesting is not +allowed. The replacement fields within the format_spec are +substituted before the *format_spec* string is interpreted. This +allows the formatting of a value to be dynamically specified. + +See the Format examples section for some examples. + + +Format Specification Mini-Language +================================== + +“Format specifications” are used within replacement fields contained +within a format string to define how individual values are presented +(see Format String Syntax and f-strings). They can also be passed +directly to the built-in "format()" function. Each formattable type +may define how the format specification is to be interpreted. + +Most built-in types implement the following options for format +specifications, although some of the formatting options are only +supported by the numeric types. + +A general convention is that an empty format specification produces +the same result as if you had called "str()" on the value. A non-empty +format specification typically modifies the result. + +The general form of a *standard format specifier* is: + + format_spec ::= [[fill]align][sign]["z"]["#"]["0"][width][grouping_option]["." precision][type] + fill ::= <any character> + align ::= "<" | ">" | "=" | "^" + sign ::= "+" | "-" | " " + width ::= digit+ + grouping_option ::= "_" | "," + precision ::= digit+ + type ::= "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%" + +If a valid *align* value is specified, it can be preceded by a *fill* +character that can be any character and defaults to a space if +omitted. It is not possible to use a literal curly brace (”"{"” or +“"}"”) as the *fill* character in a formatted string literal or when +using the "str.format()" method. However, it is possible to insert a +curly brace with a nested replacement field. This limitation doesn’t +affect the "format()" function. + +The meaning of the various alignment options is as follows: + ++-----------+------------------------------------------------------------+ +| Option | Meaning | +|===========|============================================================| +| "'<'" | Forces the field to be left-aligned within the available | +| | space (this is the default for most objects). | ++-----------+------------------------------------------------------------+ +| "'>'" | Forces the field to be right-aligned within the available | +| | space (this is the default for numbers). | ++-----------+------------------------------------------------------------+ +| "'='" | Forces the padding to be placed after the sign (if any) | +| | but before the digits. This is used for printing fields | +| | in the form ‘+000000120’. This alignment option is only | +| | valid for numeric types, excluding "complex". It becomes | +| | the default for numbers when ‘0’ immediately precedes the | +| | field width. | ++-----------+------------------------------------------------------------+ +| "'^'" | Forces the field to be centered within the available | +| | space. | ++-----------+------------------------------------------------------------+ + +Note that unless a minimum field width is defined, the field width +will always be the same size as the data to fill it, so that the +alignment option has no meaning in this case. + +The *sign* option is only valid for number types, and can be one of +the following: + ++-----------+------------------------------------------------------------+ +| Option | Meaning | +|===========|============================================================| +| "'+'" | indicates that a sign should be used for both positive as | +| | well as negative numbers. | ++-----------+------------------------------------------------------------+ +| "'-'" | indicates that a sign should be used only for negative | +| | numbers (this is the default behavior). | ++-----------+------------------------------------------------------------+ +| space | indicates that a leading space should be used on positive | +| | numbers, and a minus sign on negative numbers. | ++-----------+------------------------------------------------------------+ + +The "'z'" option coerces negative zero floating-point values to +positive zero after rounding to the format precision. This option is +only valid for floating-point presentation types. + +Changed in version 3.11: Added the "'z'" option (see also **PEP +682**). + +The "'#'" option causes the “alternate form” to be used for the +conversion. The alternate form is defined differently for different +types. This option is only valid for integer, float and complex +types. For integers, when binary, octal, or hexadecimal output is +used, this option adds the respective prefix "'0b'", "'0o'", "'0x'", +or "'0X'" to the output value. For float and complex the alternate +form causes the result of the conversion to always contain a decimal- +point character, even if no digits follow it. Normally, a decimal- +point character appears in the result of these conversions only if a +digit follows it. In addition, for "'g'" and "'G'" conversions, +trailing zeros are not removed from the result. + +The "','" option signals the use of a comma for a thousands separator +for floating-point presentation types and for integer presentation +type "'d'". For other presentation types, this option is an error. For +a locale aware separator, use the "'n'" integer presentation type +instead. + +Changed in version 3.1: Added the "','" option (see also **PEP 378**). + +The "'_'" option signals the use of an underscore for a thousands +separator for floating-point presentation types and for integer +presentation type "'d'". For integer presentation types "'b'", "'o'", +"'x'", and "'X'", underscores will be inserted every 4 digits. For +other presentation types, specifying this option is an error. + +Changed in version 3.6: Added the "'_'" option (see also **PEP 515**). + +*width* is a decimal integer defining the minimum total field width, +including any prefixes, separators, and other formatting characters. +If not specified, then the field width will be determined by the +content. + +When no explicit alignment is given, preceding the *width* field by a +zero ("'0'") character enables sign-aware zero-padding for numeric +types, excluding "complex". This is equivalent to a *fill* character +of "'0'" with an *alignment* type of "'='". + +Changed in version 3.10: Preceding the *width* field by "'0'" no +longer affects the default alignment for strings. + +The *precision* is a decimal integer indicating how many digits should +be displayed after the decimal point for presentation types "'f'" and +"'F'", or before and after the decimal point for presentation types +"'g'" or "'G'". For string presentation types the field indicates the +maximum field size - in other words, how many characters will be used +from the field content. The *precision* is not allowed for integer +presentation types. + +Finally, the *type* determines how the data should be presented. + +The available string presentation types are: + + +-----------+------------------------------------------------------------+ + | Type | Meaning | + |===========|============================================================| + | "'s'" | String format. This is the default type for strings and | + | | may be omitted. | + +-----------+------------------------------------------------------------+ + | None | The same as "'s'". | + +-----------+------------------------------------------------------------+ + +The available integer presentation types are: + + +-----------+------------------------------------------------------------+ + | Type | Meaning | + |===========|============================================================| + | "'b'" | Binary format. Outputs the number in base 2. | + +-----------+------------------------------------------------------------+ + | "'c'" | Character. Converts the integer to the corresponding | + | | unicode character before printing. | + +-----------+------------------------------------------------------------+ + | "'d'" | Decimal Integer. Outputs the number in base 10. | + +-----------+------------------------------------------------------------+ + | "'o'" | Octal format. Outputs the number in base 8. | + +-----------+------------------------------------------------------------+ + | "'x'" | Hex format. Outputs the number in base 16, using lower- | + | | case letters for the digits above 9. | + +-----------+------------------------------------------------------------+ + | "'X'" | Hex format. Outputs the number in base 16, using upper- | + | | case letters for the digits above 9. In case "'#'" is | + | | specified, the prefix "'0x'" will be upper-cased to "'0X'" | + | | as well. | + +-----------+------------------------------------------------------------+ + | "'n'" | Number. This is the same as "'d'", except that it uses the | + | | current locale setting to insert the appropriate number | + | | separator characters. | + +-----------+------------------------------------------------------------+ + | None | The same as "'d'". | + +-----------+------------------------------------------------------------+ + +In addition to the above presentation types, integers can be formatted +with the floating-point presentation types listed below (except "'n'" +and "None"). When doing so, "float()" is used to convert the integer +to a floating-point number before formatting. + +The available presentation types for "float" and "Decimal" values are: + + +-----------+------------------------------------------------------------+ + | Type | Meaning | + |===========|============================================================| + | "'e'" | Scientific notation. For a given precision "p", formats | + | | the number in scientific notation with the letter ‘e’ | + | | separating the coefficient from the exponent. The | + | | coefficient has one digit before and "p" digits after the | + | | decimal point, for a total of "p + 1" significant digits. | + | | With no precision given, uses a precision of "6" digits | + | | after the decimal point for "float", and shows all | + | | coefficient digits for "Decimal". If "p=0", the decimal | + | | point is omitted unless the "#" option is used. | + +-----------+------------------------------------------------------------+ + | "'E'" | Scientific notation. Same as "'e'" except it uses an upper | + | | case ‘E’ as the separator character. | + +-----------+------------------------------------------------------------+ + | "'f'" | Fixed-point notation. For a given precision "p", formats | + | | the number as a decimal number with exactly "p" digits | + | | following the decimal point. With no precision given, uses | + | | a precision of "6" digits after the decimal point for | + | | "float", and uses a precision large enough to show all | + | | coefficient digits for "Decimal". If "p=0", the decimal | + | | point is omitted unless the "#" option is used. | + +-----------+------------------------------------------------------------+ + | "'F'" | Fixed-point notation. Same as "'f'", but converts "nan" to | + | | "NAN" and "inf" to "INF". | + +-----------+------------------------------------------------------------+ + | "'g'" | General format. For a given precision "p >= 1", this | + | | rounds the number to "p" significant digits and then | + | | formats the result in either fixed-point format or in | + | | scientific notation, depending on its magnitude. A | + | | precision of "0" is treated as equivalent to a precision | + | | of "1". The precise rules are as follows: suppose that | + | | the result formatted with presentation type "'e'" and | + | | precision "p-1" would have exponent "exp". Then, if "m <= | + | | exp < p", where "m" is -4 for floats and -6 for | + | | "Decimals", the number is formatted with presentation type | + | | "'f'" and precision "p-1-exp". Otherwise, the number is | + | | formatted with presentation type "'e'" and precision | + | | "p-1". In both cases insignificant trailing zeros are | + | | removed from the significand, and the decimal point is | + | | also removed if there are no remaining digits following | + | | it, unless the "'#'" option is used. With no precision | + | | given, uses a precision of "6" significant digits for | + | | "float". For "Decimal", the coefficient of the result is | + | | formed from the coefficient digits of the value; | + | | scientific notation is used for values smaller than "1e-6" | + | | in absolute value and values where the place value of the | + | | least significant digit is larger than 1, and fixed-point | + | | notation is used otherwise. Positive and negative | + | | infinity, positive and negative zero, and nans, are | + | | formatted as "inf", "-inf", "0", "-0" and "nan" | + | | respectively, regardless of the precision. | + +-----------+------------------------------------------------------------+ + | "'G'" | General format. Same as "'g'" except switches to "'E'" if | + | | the number gets too large. The representations of infinity | + | | and NaN are uppercased, too. | + +-----------+------------------------------------------------------------+ + | "'n'" | Number. This is the same as "'g'", except that it uses the | + | | current locale setting to insert the appropriate number | + | | separator characters. | + +-----------+------------------------------------------------------------+ + | "'%'" | Percentage. Multiplies the number by 100 and displays in | + | | fixed ("'f'") format, followed by a percent sign. | + +-----------+------------------------------------------------------------+ + | None | For "float" this is like the "'g'" type, except that when | + | | fixed- point notation is used to format the result, it | + | | always includes at least one digit past the decimal point, | + | | and switches to the scientific notation when "exp >= p - | + | | 1". When the precision is not specified, the latter will | + | | be as large as needed to represent the given value | + | | faithfully. For "Decimal", this is the same as either | + | | "'g'" or "'G'" depending on the value of | + | | "context.capitals" for the current decimal context. The | + | | overall effect is to match the output of "str()" as | + | | altered by the other format modifiers. | + +-----------+------------------------------------------------------------+ + +The result should be correctly rounded to a given precision "p" of +digits after the decimal point. The rounding mode for "float" matches +that of the "round()" builtin. For "Decimal", the rounding mode of +the current context will be used. + +The available presentation types for "complex" are the same as those +for "float" ("'%'" is not allowed). Both the real and imaginary +components of a complex number are formatted as floating-point +numbers, according to the specified presentation type. They are +separated by the mandatory sign of the imaginary part, the latter +being terminated by a "j" suffix. If the presentation type is +missing, the result will match the output of "str()" (complex numbers +with a non-zero real part are also surrounded by parentheses), +possibly altered by other format modifiers. + + +Format examples +=============== + +This section contains examples of the "str.format()" syntax and +comparison with the old "%"-formatting. + +In most of the cases the syntax is similar to the old "%"-formatting, +with the addition of the "{}" and with ":" used instead of "%". For +example, "'%03.2f'" can be translated to "'{:03.2f}'". + +The new format syntax also supports new and different options, shown +in the following examples. + +Accessing arguments by position: + + >>> '{0}, {1}, {2}'.format('a', 'b', 'c') + 'a, b, c' + >>> '{}, {}, {}'.format('a', 'b', 'c') # 3.1+ only + 'a, b, c' + >>> '{2}, {1}, {0}'.format('a', 'b', 'c') + 'c, b, a' + >>> '{2}, {1}, {0}'.format(*'abc') # unpacking argument sequence + 'c, b, a' + >>> '{0}{1}{0}'.format('abra', 'cad') # arguments' indices can be repeated + 'abracadabra' + +Accessing arguments by name: + + >>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W') + 'Coordinates: 37.24N, -115.81W' + >>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'} + >>> 'Coordinates: {latitude}, {longitude}'.format(**coord) + 'Coordinates: 37.24N, -115.81W' + +Accessing arguments’ attributes: + + >>> c = 3-5j + >>> ('The complex number {0} is formed from the real part {0.real} ' + ... 'and the imaginary part {0.imag}.').format(c) + 'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.' + >>> class Point: + ... def __init__(self, x, y): + ... self.x, self.y = x, y + ... def __str__(self): + ... return 'Point({self.x}, {self.y})'.format(self=self) + ... + >>> str(Point(4, 2)) + 'Point(4, 2)' + +Accessing arguments’ items: + + >>> coord = (3, 5) + >>> 'X: {0[0]}; Y: {0[1]}'.format(coord) + 'X: 3; Y: 5' + +Replacing "%s" and "%r": + + >>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2') + "repr() shows quotes: 'test1'; str() doesn't: test2" + +Aligning the text and specifying a width: + + >>> '{:<30}'.format('left aligned') + 'left aligned ' + >>> '{:>30}'.format('right aligned') + ' right aligned' + >>> '{:^30}'.format('centered') + ' centered ' + >>> '{:*^30}'.format('centered') # use '*' as a fill char + '***********centered***********' + +Replacing "%+f", "%-f", and "% f" and specifying a sign: + + >>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it always + '+3.140000; -3.140000' + >>> '{: f}; {: f}'.format(3.14, -3.14) # show a space for positive numbers + ' 3.140000; -3.140000' + >>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the minus -- same as '{:f}; {:f}' + '3.140000; -3.140000' + +Replacing "%x" and "%o" and converting the value to different bases: + + >>> # format also supports binary numbers + >>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}".format(42) + 'int: 42; hex: 2a; oct: 52; bin: 101010' + >>> # with 0x, 0o, or 0b as prefix: + >>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42) + 'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010' + +Using the comma as a thousands separator: + + >>> '{:,}'.format(1234567890) + '1,234,567,890' + +Expressing a percentage: + + >>> points = 19 + >>> total = 22 + >>> 'Correct answers: {:.2%}'.format(points/total) + 'Correct answers: 86.36%' + +Using type-specific formatting: + + >>> import datetime + >>> d = datetime.datetime(2010, 7, 4, 12, 15, 58) + >>> '{:%Y-%m-%d %H:%M:%S}'.format(d) + '2010-07-04 12:15:58' + +Nesting arguments and more complex examples: + + >>> for align, text in zip('<^>', ['left', 'center', 'right']): + ... '{0:{fill}{align}16}'.format(text, fill=align, align=align) + ... + 'left<<<<<<<<<<<<' + '^^^^^center^^^^^' + '>>>>>>>>>>>right' + >>> + >>> octets = [192, 168, 0, 1] + >>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets) + 'C0A80001' + >>> int(_, 16) + 3232235521 + >>> + >>> width = 5 + >>> for num in range(5,12): + ... for base in 'dXob': + ... print('{0:{width}{base}}'.format(num, base=base, width=width), end=' ') + ... print() + ... + 5 5 5 101 + 6 6 6 110 + 7 7 7 111 + 8 8 10 1000 + 9 9 11 1001 + 10 A 12 1010 + 11 B 13 1011 +''', + 'function': r'''Function definitions +******************** + +A function definition defines a user-defined function object (see +section The standard type hierarchy): + + funcdef ::= [decorators] "def" funcname [type_params] "(" [parameter_list] ")" + ["->" expression] ":" suite + decorators ::= decorator+ + decorator ::= "@" assignment_expression NEWLINE + parameter_list ::= defparameter ("," defparameter)* "," "/" ["," [parameter_list_no_posonly]] + | parameter_list_no_posonly + parameter_list_no_posonly ::= defparameter ("," defparameter)* ["," [parameter_list_starargs]] + | parameter_list_starargs + parameter_list_starargs ::= "*" [star_parameter] ("," defparameter)* ["," ["**" parameter [","]]] + | "**" parameter [","] + parameter ::= identifier [":" expression] + star_parameter ::= identifier [":" ["*"] expression] + defparameter ::= parameter ["=" expression] + funcname ::= identifier + +A function definition is an executable statement. Its execution binds +the function name in the current local namespace to a function object +(a wrapper around the executable code for the function). This +function object contains a reference to the current global namespace +as the global namespace to be used when the function is called. + +The function definition does not execute the function body; this gets +executed only when the function is called. [4] + +A function definition may be wrapped by one or more *decorator* +expressions. Decorator expressions are evaluated when the function is +defined, in the scope that contains the function definition. The +result must be a callable, which is invoked with the function object +as the only argument. The returned value is bound to the function name +instead of the function object. Multiple decorators are applied in +nested fashion. For example, the following code + + @f1(arg) + @f2 + def func(): pass + +is roughly equivalent to + + def func(): pass + func = f1(arg)(f2(func)) + +except that the original function is not temporarily bound to the name +"func". + +Changed in version 3.9: Functions may be decorated with any valid +"assignment_expression". Previously, the grammar was much more +restrictive; see **PEP 614** for details. + +A list of type parameters may be given in square brackets between the +function’s name and the opening parenthesis for its parameter list. +This indicates to static type checkers that the function is generic. +At runtime, the type parameters can be retrieved from the function’s +"__type_params__" attribute. See Generic functions for more. + +Changed in version 3.12: Type parameter lists are new in Python 3.12. + +When one or more *parameters* have the form *parameter* "=" +*expression*, the function is said to have “default parameter values.” +For a parameter with a default value, the corresponding *argument* may +be omitted from a call, in which case the parameter’s default value is +substituted. If a parameter has a default value, all following +parameters up until the “"*"” must also have a default value — this is +a syntactic restriction that is not expressed by the grammar. + +**Default parameter values are evaluated from left to right when the +function definition is executed.** This means that the expression is +evaluated once, when the function is defined, and that the same “pre- +computed” value is used for each call. This is especially important +to understand when a default parameter value is a mutable object, such +as a list or a dictionary: if the function modifies the object (e.g. +by appending an item to a list), the default parameter value is in +effect modified. This is generally not what was intended. A way +around this is to use "None" as the default, and explicitly test for +it in the body of the function, e.g.: + + def whats_on_the_telly(penguin=None): + if penguin is None: + penguin = [] + penguin.append("property of the zoo") + return penguin + +Function call semantics are described in more detail in section Calls. +A function call always assigns values to all parameters mentioned in +the parameter list, either from positional arguments, from keyword +arguments, or from default values. If the form “"*identifier"” is +present, it is initialized to a tuple receiving any excess positional +parameters, defaulting to the empty tuple. If the form +“"**identifier"” is present, it is initialized to a new ordered +mapping receiving any excess keyword arguments, defaulting to a new +empty mapping of the same type. Parameters after “"*"” or +“"*identifier"” are keyword-only parameters and may only be passed by +keyword arguments. Parameters before “"/"” are positional-only +parameters and may only be passed by positional arguments. + +Changed in version 3.8: The "/" function parameter syntax may be used +to indicate positional-only parameters. See **PEP 570** for details. + +Parameters may have an *annotation* of the form “": expression"” +following the parameter name. Any parameter may have an annotation, +even those of the form "*identifier" or "**identifier". (As a special +case, parameters of the form "*identifier" may have an annotation “": +*expression"”.) Functions may have “return” annotation of the form +“"-> expression"” after the parameter list. These annotations can be +any valid Python expression. The presence of annotations does not +change the semantics of a function. See Annotations for more +information on annotations. + +Changed in version 3.11: Parameters of the form “"*identifier"” may +have an annotation “": *expression"”. See **PEP 646**. + +It is also possible to create anonymous functions (functions not bound +to a name), for immediate use in expressions. This uses lambda +expressions, described in section Lambdas. Note that the lambda +expression is merely a shorthand for a simplified function definition; +a function defined in a “"def"” statement can be passed around or +assigned to another name just like a function defined by a lambda +expression. The “"def"” form is actually more powerful since it +allows the execution of multiple statements and annotations. + +**Programmer’s note:** Functions are first-class objects. A “"def"” +statement executed inside a function definition defines a local +function that can be returned or passed around. Free variables used +in the nested function can access the local variables of the function +containing the def. See section Naming and binding for details. + +See also: + + **PEP 3107** - Function Annotations + The original specification for function annotations. + + **PEP 484** - Type Hints + Definition of a standard meaning for annotations: type hints. + + **PEP 526** - Syntax for Variable Annotations + Ability to type hint variable declarations, including class + variables and instance variables. + + **PEP 563** - Postponed Evaluation of Annotations + Support for forward references within annotations by preserving + annotations in a string form at runtime instead of eager + evaluation. + + **PEP 318** - Decorators for Functions and Methods + Function and method decorators were introduced. Class decorators + were introduced in **PEP 3129**. +''', + 'global': r'''The "global" statement +********************** + + global_stmt ::= "global" identifier ("," identifier)* + +The "global" statement causes the listed identifiers to be interpreted +as globals. It would be impossible to assign to a global variable +without "global", although free variables may refer to globals without +being declared global. + +The "global" statement applies to the entire scope of a function or +class body. A "SyntaxError" is raised if a variable is used or +assigned to prior to its global declaration in the scope. + +**Programmer’s note:** "global" is a directive to the parser. It +applies only to code parsed at the same time as the "global" +statement. In particular, a "global" statement contained in a string +or code object supplied to the built-in "exec()" function does not +affect the code block *containing* the function call, and code +contained in such a string is unaffected by "global" statements in the +code containing the function call. The same applies to the "eval()" +and "compile()" functions. +''', + 'id-classes': r'''Reserved classes of identifiers +******************************* + +Certain classes of identifiers (besides keywords) have special +meanings. These classes are identified by the patterns of leading and +trailing underscore characters: + +"_*" + Not imported by "from module import *". + +"_" + In a "case" pattern within a "match" statement, "_" is a soft + keyword that denotes a wildcard. + + Separately, the interactive interpreter makes the result of the + last evaluation available in the variable "_". (It is stored in the + "builtins" module, alongside built-in functions like "print".) + + Elsewhere, "_" is a regular identifier. It is often used to name + “special” items, but it is not special to Python itself. + + Note: + + The name "_" is often used in conjunction with + internationalization; refer to the documentation for the + "gettext" module for more information on this convention.It is + also commonly used for unused variables. + +"__*__" + System-defined names, informally known as “dunder” names. These + names are defined by the interpreter and its implementation + (including the standard library). Current system names are + discussed in the Special method names section and elsewhere. More + will likely be defined in future versions of Python. *Any* use of + "__*__" names, in any context, that does not follow explicitly + documented use, is subject to breakage without warning. + +"__*" + Class-private names. Names in this category, when used within the + context of a class definition, are re-written to use a mangled form + to help avoid name clashes between “private” attributes of base and + derived classes. See section Identifiers (Names). +''', + 'identifiers': r'''Identifiers and keywords +************************ + +Identifiers (also referred to as *names*) are described by the +following lexical definitions. + +The syntax of identifiers in Python is based on the Unicode standard +annex UAX-31, with elaboration and changes as defined below; see also +**PEP 3131** for further details. + +Within the ASCII range (U+0001..U+007F), the valid characters for +identifiers include the uppercase and lowercase letters "A" through +"Z", the underscore "_" and, except for the first character, the +digits "0" through "9". Python 3.0 introduced additional characters +from outside the ASCII range (see **PEP 3131**). For these +characters, the classification uses the version of the Unicode +Character Database as included in the "unicodedata" module. + +Identifiers are unlimited in length. Case is significant. + + identifier ::= xid_start xid_continue* + id_start ::= <all characters in general categories Lu, Ll, Lt, Lm, Lo, Nl, the underscore, and characters with the Other_ID_Start property> + id_continue ::= <all characters in id_start, plus characters in the categories Mn, Mc, Nd, Pc and others with the Other_ID_Continue property> + xid_start ::= <all characters in id_start whose NFKC normalization is in "id_start xid_continue*"> + xid_continue ::= <all characters in id_continue whose NFKC normalization is in "id_continue*"> + +The Unicode category codes mentioned above stand for: + +* *Lu* - uppercase letters + +* *Ll* - lowercase letters + +* *Lt* - titlecase letters + +* *Lm* - modifier letters + +* *Lo* - other letters + +* *Nl* - letter numbers + +* *Mn* - nonspacing marks + +* *Mc* - spacing combining marks + +* *Nd* - decimal numbers + +* *Pc* - connector punctuations + +* *Other_ID_Start* - explicit list of characters in PropList.txt to + support backwards compatibility + +* *Other_ID_Continue* - likewise + +All identifiers are converted into the normal form NFKC while parsing; +comparison of identifiers is based on NFKC. + +A non-normative HTML file listing all valid identifier characters for +Unicode 16.0.0 can be found at +https://www.unicode.org/Public/16.0.0/ucd/DerivedCoreProperties.txt + + +Keywords +======== + +The following identifiers are used as reserved words, or *keywords* of +the language, and cannot be used as ordinary identifiers. They must +be spelled exactly as written here: + + False await else import pass + None break except in raise + True class finally is return + and continue for lambda try + as def from nonlocal while + assert del global not with + async elif if or yield + + +Soft Keywords +============= + +Added in version 3.10. + +Some identifiers are only reserved under specific contexts. These are +known as *soft keywords*. The identifiers "match", "case", "type" and +"_" can syntactically act as keywords in certain contexts, but this +distinction is done at the parser level, not when tokenizing. + +As soft keywords, their use in the grammar is possible while still +preserving compatibility with existing code that uses these names as +identifier names. + +"match", "case", and "_" are used in the "match" statement. "type" is +used in the "type" statement. + +Changed in version 3.12: "type" is now a soft keyword. + + +Reserved classes of identifiers +=============================== + +Certain classes of identifiers (besides keywords) have special +meanings. These classes are identified by the patterns of leading and +trailing underscore characters: + +"_*" + Not imported by "from module import *". + +"_" + In a "case" pattern within a "match" statement, "_" is a soft + keyword that denotes a wildcard. + + Separately, the interactive interpreter makes the result of the + last evaluation available in the variable "_". (It is stored in the + "builtins" module, alongside built-in functions like "print".) + + Elsewhere, "_" is a regular identifier. It is often used to name + “special” items, but it is not special to Python itself. + + Note: + + The name "_" is often used in conjunction with + internationalization; refer to the documentation for the + "gettext" module for more information on this convention.It is + also commonly used for unused variables. + +"__*__" + System-defined names, informally known as “dunder” names. These + names are defined by the interpreter and its implementation + (including the standard library). Current system names are + discussed in the Special method names section and elsewhere. More + will likely be defined in future versions of Python. *Any* use of + "__*__" names, in any context, that does not follow explicitly + documented use, is subject to breakage without warning. + +"__*" + Class-private names. Names in this category, when used within the + context of a class definition, are re-written to use a mangled form + to help avoid name clashes between “private” attributes of base and + derived classes. See section Identifiers (Names). +''', + 'if': r'''The "if" statement +****************** + +The "if" statement is used for conditional execution: + + if_stmt ::= "if" assignment_expression ":" suite + ("elif" assignment_expression ":" suite)* + ["else" ":" suite] + +It selects exactly one of the suites by evaluating the expressions one +by one until one is found to be true (see section Boolean operations +for the definition of true and false); then that suite is executed +(and no other part of the "if" statement is executed or evaluated). +If all expressions are false, the suite of the "else" clause, if +present, is executed. +''', + 'imaginary': r'''Imaginary literals +****************** + +Imaginary literals are described by the following lexical definitions: + + imagnumber ::= (floatnumber | digitpart) ("j" | "J") + +An imaginary literal yields a complex number with a real part of 0.0. +Complex numbers are represented as a pair of floating-point numbers +and have the same restrictions on their range. To create a complex +number with a nonzero real part, add a floating-point number to it, +e.g., "(3+4j)". Some examples of imaginary literals: + + 3.14j 10.j 10j .001j 1e100j 3.14e-10j 3.14_15_93j +''', + 'import': r'''The "import" statement +********************** + + import_stmt ::= "import" module ["as" identifier] ("," module ["as" identifier])* + | "from" relative_module "import" identifier ["as" identifier] + ("," identifier ["as" identifier])* + | "from" relative_module "import" "(" identifier ["as" identifier] + ("," identifier ["as" identifier])* [","] ")" + | "from" relative_module "import" "*" + module ::= (identifier ".")* identifier + relative_module ::= "."* module | "."+ + +The basic import statement (no "from" clause) is executed in two +steps: + +1. find a module, loading and initializing it if necessary + +2. define a name or names in the local namespace for the scope where + the "import" statement occurs. + +When the statement contains multiple clauses (separated by commas) the +two steps are carried out separately for each clause, just as though +the clauses had been separated out into individual import statements. + +The details of the first step, finding and loading modules, are +described in greater detail in the section on the import system, which +also describes the various types of packages and modules that can be +imported, as well as all the hooks that can be used to customize the +import system. Note that failures in this step may indicate either +that the module could not be located, *or* that an error occurred +while initializing the module, which includes execution of the +module’s code. + +If the requested module is retrieved successfully, it will be made +available in the local namespace in one of three ways: + +* If the module name is followed by "as", then the name following "as" + is bound directly to the imported module. + +* If no other name is specified, and the module being imported is a + top level module, the module’s name is bound in the local namespace + as a reference to the imported module + +* If the module being imported is *not* a top level module, then the + name of the top level package that contains the module is bound in + the local namespace as a reference to the top level package. The + imported module must be accessed using its full qualified name + rather than directly + +The "from" form uses a slightly more complex process: + +1. find the module specified in the "from" clause, loading and + initializing it if necessary; + +2. for each of the identifiers specified in the "import" clauses: + + 1. check if the imported module has an attribute by that name + + 2. if not, attempt to import a submodule with that name and then + check the imported module again for that attribute + + 3. if the attribute is not found, "ImportError" is raised. + + 4. otherwise, a reference to that value is stored in the local + namespace, using the name in the "as" clause if it is present, + otherwise using the attribute name + +Examples: + + import foo # foo imported and bound locally + import foo.bar.baz # foo, foo.bar, and foo.bar.baz imported, foo bound locally + import foo.bar.baz as fbb # foo, foo.bar, and foo.bar.baz imported, foo.bar.baz bound as fbb + from foo.bar import baz # foo, foo.bar, and foo.bar.baz imported, foo.bar.baz bound as baz + from foo import attr # foo imported and foo.attr bound as attr + +If the list of identifiers is replaced by a star ("'*'"), all public +names defined in the module are bound in the local namespace for the +scope where the "import" statement occurs. + +The *public names* defined by a module are determined by checking the +module’s namespace for a variable named "__all__"; if defined, it must +be a sequence of strings which are names defined or imported by that +module. The names given in "__all__" are all considered public and +are required to exist. If "__all__" is not defined, the set of public +names includes all names found in the module’s namespace which do not +begin with an underscore character ("'_'"). "__all__" should contain +the entire public API. It is intended to avoid accidentally exporting +items that are not part of the API (such as library modules which were +imported and used within the module). + +The wild card form of import — "from module import *" — is only +allowed at the module level. Attempting to use it in class or +function definitions will raise a "SyntaxError". + +When specifying what module to import you do not have to specify the +absolute name of the module. When a module or package is contained +within another package it is possible to make a relative import within +the same top package without having to mention the package name. By +using leading dots in the specified module or package after "from" you +can specify how high to traverse up the current package hierarchy +without specifying exact names. One leading dot means the current +package where the module making the import exists. Two dots means up +one package level. Three dots is up two levels, etc. So if you execute +"from . import mod" from a module in the "pkg" package then you will +end up importing "pkg.mod". If you execute "from ..subpkg2 import mod" +from within "pkg.subpkg1" you will import "pkg.subpkg2.mod". The +specification for relative imports is contained in the Package +Relative Imports section. + +"importlib.import_module()" is provided to support applications that +determine dynamically the modules to be loaded. + +Raises an auditing event "import" with arguments "module", "filename", +"sys.path", "sys.meta_path", "sys.path_hooks". + + +Future statements +================= + +A *future statement* is a directive to the compiler that a particular +module should be compiled using syntax or semantics that will be +available in a specified future release of Python where the feature +becomes standard. + +The future statement is intended to ease migration to future versions +of Python that introduce incompatible changes to the language. It +allows use of the new features on a per-module basis before the +release in which the feature becomes standard. + + future_stmt ::= "from" "__future__" "import" feature ["as" identifier] + ("," feature ["as" identifier])* + | "from" "__future__" "import" "(" feature ["as" identifier] + ("," feature ["as" identifier])* [","] ")" + feature ::= identifier + +A future statement must appear near the top of the module. The only +lines that can appear before a future statement are: + +* the module docstring (if any), + +* comments, + +* blank lines, and + +* other future statements. + +The only feature that requires using the future statement is +"annotations" (see **PEP 563**). + +All historical features enabled by the future statement are still +recognized by Python 3. The list includes "absolute_import", +"division", "generators", "generator_stop", "unicode_literals", +"print_function", "nested_scopes" and "with_statement". They are all +redundant because they are always enabled, and only kept for backwards +compatibility. + +A future statement is recognized and treated specially at compile +time: Changes to the semantics of core constructs are often +implemented by generating different code. It may even be the case +that a new feature introduces new incompatible syntax (such as a new +reserved word), in which case the compiler may need to parse the +module differently. Such decisions cannot be pushed off until +runtime. + +For any given release, the compiler knows which feature names have +been defined, and raises a compile-time error if a future statement +contains a feature not known to it. + +The direct runtime semantics are the same as for any import statement: +there is a standard module "__future__", described later, and it will +be imported in the usual way at the time the future statement is +executed. + +The interesting runtime semantics depend on the specific feature +enabled by the future statement. + +Note that there is nothing special about the statement: + + import __future__ [as name] + +That is not a future statement; it’s an ordinary import statement with +no special semantics or syntax restrictions. + +Code compiled by calls to the built-in functions "exec()" and +"compile()" that occur in a module "M" containing a future statement +will, by default, use the new syntax or semantics associated with the +future statement. This can be controlled by optional arguments to +"compile()" — see the documentation of that function for details. + +A future statement typed at an interactive interpreter prompt will +take effect for the rest of the interpreter session. If an +interpreter is started with the "-i" option, is passed a script name +to execute, and the script includes a future statement, it will be in +effect in the interactive session started after the script is +executed. + +See also: + + **PEP 236** - Back to the __future__ + The original proposal for the __future__ mechanism. +''', + 'in': r'''Membership test operations +************************** + +The operators "in" and "not in" test for membership. "x in s" +evaluates to "True" if *x* is a member of *s*, and "False" otherwise. +"x not in s" returns the negation of "x in s". All built-in sequences +and set types support this as well as dictionary, for which "in" tests +whether the dictionary has a given key. For container types such as +list, tuple, set, frozenset, dict, or collections.deque, the +expression "x in y" is equivalent to "any(x is e or x == e for e in +y)". + +For the string and bytes types, "x in y" is "True" if and only if *x* +is a substring of *y*. An equivalent test is "y.find(x) != -1". +Empty strings are always considered to be a substring of any other +string, so """ in "abc"" will return "True". + +For user-defined classes which define the "__contains__()" method, "x +in y" returns "True" if "y.__contains__(x)" returns a true value, and +"False" otherwise. + +For user-defined classes which do not define "__contains__()" but do +define "__iter__()", "x in y" is "True" if some value "z", for which +the expression "x is z or x == z" is true, is produced while iterating +over "y". If an exception is raised during the iteration, it is as if +"in" raised that exception. + +Lastly, the old-style iteration protocol is tried: if a class defines +"__getitem__()", "x in y" is "True" if and only if there is a non- +negative integer index *i* such that "x is y[i] or x == y[i]", and no +lower integer index raises the "IndexError" exception. (If any other +exception is raised, it is as if "in" raised that exception). + +The operator "not in" is defined to have the inverse truth value of +"in". +''', + 'integers': r'''Integer literals +**************** + +Integer literals are described by the following lexical definitions: + + integer ::= decinteger | bininteger | octinteger | hexinteger + decinteger ::= nonzerodigit (["_"] digit)* | "0"+ (["_"] "0")* + bininteger ::= "0" ("b" | "B") (["_"] bindigit)+ + octinteger ::= "0" ("o" | "O") (["_"] octdigit)+ + hexinteger ::= "0" ("x" | "X") (["_"] hexdigit)+ + nonzerodigit ::= "1"..."9" + digit ::= "0"..."9" + bindigit ::= "0" | "1" + octdigit ::= "0"..."7" + hexdigit ::= digit | "a"..."f" | "A"..."F" + +There is no limit for the length of integer literals apart from what +can be stored in available memory. + +Underscores are ignored for determining the numeric value of the +literal. They can be used to group digits for enhanced readability. +One underscore can occur between digits, and after base specifiers +like "0x". + +Note that leading zeros in a non-zero decimal number are not allowed. +This is for disambiguation with C-style octal literals, which Python +used before version 3.0. + +Some examples of integer literals: + + 7 2147483647 0o177 0b100110111 + 3 79228162514264337593543950336 0o377 0xdeadbeef + 100_000_000_000 0b_1110_0101 + +Changed in version 3.6: Underscores are now allowed for grouping +purposes in literals. +''', + 'lambda': r'''Lambdas +******* + + lambda_expr ::= "lambda" [parameter_list] ":" expression + +Lambda expressions (sometimes called lambda forms) are used to create +anonymous functions. The expression "lambda parameters: expression" +yields a function object. The unnamed object behaves like a function +object defined with: + + def <lambda>(parameters): + return expression + +See section Function definitions for the syntax of parameter lists. +Note that functions created with lambda expressions cannot contain +statements or annotations. +''', + 'lists': r'''List displays +************* + +A list display is a possibly empty series of expressions enclosed in +square brackets: + + list_display ::= "[" [flexible_expression_list | comprehension] "]" + +A list display yields a new list object, the contents being specified +by either a list of expressions or a comprehension. When a comma- +separated list of expressions is supplied, its elements are evaluated +from left to right and placed into the list object in that order. +When a comprehension is supplied, the list is constructed from the +elements resulting from the comprehension. +''', + 'naming': r'''Naming and binding +****************** + + +Binding of names +================ + +*Names* refer to objects. Names are introduced by name binding +operations. + +The following constructs bind names: + +* formal parameters to functions, + +* class definitions, + +* function definitions, + +* assignment expressions, + +* targets that are identifiers if occurring in an assignment: + + * "for" loop header, + + * after "as" in a "with" statement, "except" clause, "except*" + clause, or in the as-pattern in structural pattern matching, + + * in a capture pattern in structural pattern matching + +* "import" statements. + +* "type" statements. + +* type parameter lists. + +The "import" statement of the form "from ... import *" binds all names +defined in the imported module, except those beginning with an +underscore. This form may only be used at the module level. + +A target occurring in a "del" statement is also considered bound for +this purpose (though the actual semantics are to unbind the name). + +Each assignment or import statement occurs within a block defined by a +class or function definition or at the module level (the top-level +code block). + +If a name is bound in a block, it is a local variable of that block, +unless declared as "nonlocal" or "global". If a name is bound at the +module level, it is a global variable. (The variables of the module +code block are local and global.) If a variable is used in a code +block but not defined there, it is a *free variable*. + +Each occurrence of a name in the program text refers to the *binding* +of that name established by the following name resolution rules. + + +Resolution of names +=================== + +A *scope* defines the visibility of a name within a block. If a local +variable is defined in a block, its scope includes that block. If the +definition occurs in a function block, the scope extends to any blocks +contained within the defining one, unless a contained block introduces +a different binding for the name. + +When a name is used in a code block, it is resolved using the nearest +enclosing scope. The set of all such scopes visible to a code block +is called the block’s *environment*. + +When a name is not found at all, a "NameError" exception is raised. If +the current scope is a function scope, and the name refers to a local +variable that has not yet been bound to a value at the point where the +name is used, an "UnboundLocalError" exception is raised. +"UnboundLocalError" is a subclass of "NameError". + +If a name binding operation occurs anywhere within a code block, all +uses of the name within the block are treated as references to the +current block. This can lead to errors when a name is used within a +block before it is bound. This rule is subtle. Python lacks +declarations and allows name binding operations to occur anywhere +within a code block. The local variables of a code block can be +determined by scanning the entire text of the block for name binding +operations. See the FAQ entry on UnboundLocalError for examples. + +If the "global" statement occurs within a block, all uses of the names +specified in the statement refer to the bindings of those names in the +top-level namespace. Names are resolved in the top-level namespace by +searching the global namespace, i.e. the namespace of the module +containing the code block, and the builtins namespace, the namespace +of the module "builtins". The global namespace is searched first. If +the names are not found there, the builtins namespace is searched +next. If the names are also not found in the builtins namespace, new +variables are created in the global namespace. The global statement +must precede all uses of the listed names. + +The "global" statement has the same scope as a name binding operation +in the same block. If the nearest enclosing scope for a free variable +contains a global statement, the free variable is treated as a global. + +The "nonlocal" statement causes corresponding names to refer to +previously bound variables in the nearest enclosing function scope. +"SyntaxError" is raised at compile time if the given name does not +exist in any enclosing function scope. Type parameters cannot be +rebound with the "nonlocal" statement. + +The namespace for a module is automatically created the first time a +module is imported. The main module for a script is always called +"__main__". + +Class definition blocks and arguments to "exec()" and "eval()" are +special in the context of name resolution. A class definition is an +executable statement that may use and define names. These references +follow the normal rules for name resolution with an exception that +unbound local variables are looked up in the global namespace. The +namespace of the class definition becomes the attribute dictionary of +the class. The scope of names defined in a class block is limited to +the class block; it does not extend to the code blocks of methods. +This includes comprehensions and generator expressions, but it does +not include annotation scopes, which have access to their enclosing +class scopes. This means that the following will fail: + + class A: + a = 42 + b = list(a + i for i in range(10)) + +However, the following will succeed: + + class A: + type Alias = Nested + class Nested: pass + + print(A.Alias.__value__) # <type 'A.Nested'> + + +Annotation scopes +================= + +*Annotations*, type parameter lists and "type" statements introduce +*annotation scopes*, which behave mostly like function scopes, but +with some exceptions discussed below. + +Annotation scopes are used in the following contexts: + +* *Function annotations*. + +* *Variable annotations*. + +* Type parameter lists for generic type aliases. + +* Type parameter lists for generic functions. A generic function’s + annotations are executed within the annotation scope, but its + defaults and decorators are not. + +* Type parameter lists for generic classes. A generic class’s base + classes and keyword arguments are executed within the annotation + scope, but its decorators are not. + +* The bounds, constraints, and default values for type parameters + (lazily evaluated). + +* The value of type aliases (lazily evaluated). + +Annotation scopes differ from function scopes in the following ways: + +* Annotation scopes have access to their enclosing class namespace. If + an annotation scope is immediately within a class scope, or within + another annotation scope that is immediately within a class scope, + the code in the annotation scope can use names defined in the class + scope as if it were executed directly within the class body. This + contrasts with regular functions defined within classes, which + cannot access names defined in the class scope. + +* Expressions in annotation scopes cannot contain "yield", "yield + from", "await", or ":=" expressions. (These expressions are allowed + in other scopes contained within the annotation scope.) + +* Names defined in annotation scopes cannot be rebound with "nonlocal" + statements in inner scopes. This includes only type parameters, as + no other syntactic elements that can appear within annotation scopes + can introduce new names. + +* While annotation scopes have an internal name, that name is not + reflected in the *qualified name* of objects defined within the + scope. Instead, the "__qualname__" of such objects is as if the + object were defined in the enclosing scope. + +Added in version 3.12: Annotation scopes were introduced in Python +3.12 as part of **PEP 695**. + +Changed in version 3.13: Annotation scopes are also used for type +parameter defaults, as introduced by **PEP 696**. + +Changed in version 3.14: Annotation scopes are now also used for +annotations, as specified in **PEP 649** and **PEP 749**. + + +Lazy evaluation +=============== + +Most annotation scopes are *lazily evaluated*. This includes +annotations, the values of type aliases created through the "type" +statement, and the bounds, constraints, and default values of type +variables created through the type parameter syntax. This means that +they are not evaluated when the type alias or type variable is +created, or when the object carrying annotations is created. Instead, +they are only evaluated when necessary, for example when the +"__value__" attribute on a type alias is accessed. + +Example: + + >>> type Alias = 1/0 + >>> Alias.__value__ + Traceback (most recent call last): + ... + ZeroDivisionError: division by zero + >>> def func[T: 1/0](): pass + >>> T = func.__type_params__[0] + >>> T.__bound__ + Traceback (most recent call last): + ... + ZeroDivisionError: division by zero + +Here the exception is raised only when the "__value__" attribute of +the type alias or the "__bound__" attribute of the type variable is +accessed. + +This behavior is primarily useful for references to types that have +not yet been defined when the type alias or type variable is created. +For example, lazy evaluation enables creation of mutually recursive +type aliases: + + from typing import Literal + + type SimpleExpr = int | Parenthesized + type Parenthesized = tuple[Literal["("], Expr, Literal[")"]] + type Expr = SimpleExpr | tuple[SimpleExpr, Literal["+", "-"], Expr] + +Lazily evaluated values are evaluated in annotation scope, which means +that names that appear inside the lazily evaluated value are looked up +as if they were used in the immediately enclosing scope. + +Added in version 3.12. + + +Builtins and restricted execution +================================= + +**CPython implementation detail:** Users should not touch +"__builtins__"; it is strictly an implementation detail. Users +wanting to override values in the builtins namespace should "import" +the "builtins" module and modify its attributes appropriately. + +The builtins namespace associated with the execution of a code block +is actually found by looking up the name "__builtins__" in its global +namespace; this should be a dictionary or a module (in the latter case +the module’s dictionary is used). By default, when in the "__main__" +module, "__builtins__" is the built-in module "builtins"; when in any +other module, "__builtins__" is an alias for the dictionary of the +"builtins" module itself. + + +Interaction with dynamic features +================================= + +Name resolution of free variables occurs at runtime, not at compile +time. This means that the following code will print 42: + + i = 10 + def f(): + print(i) + i = 42 + f() + +The "eval()" and "exec()" functions do not have access to the full +environment for resolving names. Names may be resolved in the local +and global namespaces of the caller. Free variables are not resolved +in the nearest enclosing namespace, but in the global namespace. [1] +The "exec()" and "eval()" functions have optional arguments to +override the global and local namespace. If only one namespace is +specified, it is used for both. +''', + 'nonlocal': r'''The "nonlocal" statement +************************ + + nonlocal_stmt ::= "nonlocal" identifier ("," identifier)* + +When the definition of a function or class is nested (enclosed) within +the definitions of other functions, its nonlocal scopes are the local +scopes of the enclosing functions. The "nonlocal" statement causes the +listed identifiers to refer to names previously bound in nonlocal +scopes. It allows encapsulated code to rebind such nonlocal +identifiers. If a name is bound in more than one nonlocal scope, the +nearest binding is used. If a name is not bound in any nonlocal scope, +or if there is no nonlocal scope, a "SyntaxError" is raised. + +The "nonlocal" statement applies to the entire scope of a function or +class body. A "SyntaxError" is raised if a variable is used or +assigned to prior to its nonlocal declaration in the scope. + +See also: + + **PEP 3104** - Access to Names in Outer Scopes + The specification for the "nonlocal" statement. + +**Programmer’s note:** "nonlocal" is a directive to the parser and +applies only to code parsed along with it. See the note for the +"global" statement. +''', + 'numbers': r'''Numeric literals +**************** + +There are three types of numeric literals: integers, floating-point +numbers, and imaginary numbers. There are no complex literals +(complex numbers can be formed by adding a real number and an +imaginary number). + +Note that numeric literals do not include a sign; a phrase like "-1" +is actually an expression composed of the unary operator ‘"-"’ and the +literal "1". +''', + 'numeric-types': r'''Emulating numeric types +*********************** + +The following methods can be defined to emulate numeric objects. +Methods corresponding to operations that are not supported by the +particular kind of number implemented (e.g., bitwise operations for +non-integral numbers) should be left undefined. + +object.__add__(self, other) +object.__sub__(self, other) +object.__mul__(self, other) +object.__matmul__(self, other) +object.__truediv__(self, other) +object.__floordiv__(self, other) +object.__mod__(self, other) +object.__divmod__(self, other) +object.__pow__(self, other[, modulo]) +object.__lshift__(self, other) +object.__rshift__(self, other) +object.__and__(self, other) +object.__xor__(self, other) +object.__or__(self, other) + + These methods are called to implement the binary arithmetic + operations ("+", "-", "*", "@", "/", "//", "%", "divmod()", + "pow()", "**", "<<", ">>", "&", "^", "|"). For instance, to + evaluate the expression "x + y", where *x* is an instance of a + class that has an "__add__()" method, "type(x).__add__(x, y)" is + called. The "__divmod__()" method should be the equivalent to + using "__floordiv__()" and "__mod__()"; it should not be related to + "__truediv__()". Note that "__pow__()" should be defined to accept + an optional third argument if the ternary version of the built-in + "pow()" function is to be supported. + + If one of those methods does not support the operation with the + supplied arguments, it should return "NotImplemented". + +object.__radd__(self, other) +object.__rsub__(self, other) +object.__rmul__(self, other) +object.__rmatmul__(self, other) +object.__rtruediv__(self, other) +object.__rfloordiv__(self, other) +object.__rmod__(self, other) +object.__rdivmod__(self, other) +object.__rpow__(self, other[, modulo]) +object.__rlshift__(self, other) +object.__rrshift__(self, other) +object.__rand__(self, other) +object.__rxor__(self, other) +object.__ror__(self, other) + + These methods are called to implement the binary arithmetic + operations ("+", "-", "*", "@", "/", "//", "%", "divmod()", + "pow()", "**", "<<", ">>", "&", "^", "|") with reflected (swapped) + operands. These functions are only called if the operands are of + different types, when the left operand does not support the + corresponding operation [3], or the right operand’s class is + derived from the left operand’s class. [4] For instance, to + evaluate the expression "x - y", where *y* is an instance of a + class that has an "__rsub__()" method, "type(y).__rsub__(y, x)" is + called if "type(x).__sub__(x, y)" returns "NotImplemented" or + "type(y)" is a subclass of "type(x)". [5] + + Note that ternary "pow()" will not try calling "__rpow__()" (the + coercion rules would become too complicated). + + Note: + + If the right operand’s type is a subclass of the left operand’s + type and that subclass provides a different implementation of the + reflected method for the operation, this method will be called + before the left operand’s non-reflected method. This behavior + allows subclasses to override their ancestors’ operations. + +object.__iadd__(self, other) +object.__isub__(self, other) +object.__imul__(self, other) +object.__imatmul__(self, other) +object.__itruediv__(self, other) +object.__ifloordiv__(self, other) +object.__imod__(self, other) +object.__ipow__(self, other[, modulo]) +object.__ilshift__(self, other) +object.__irshift__(self, other) +object.__iand__(self, other) +object.__ixor__(self, other) +object.__ior__(self, other) + + These methods are called to implement the augmented arithmetic + assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", "**=", + "<<=", ">>=", "&=", "^=", "|="). These methods should attempt to + do the operation in-place (modifying *self*) and return the result + (which could be, but does not have to be, *self*). If a specific + method is not defined, or if that method returns "NotImplemented", + the augmented assignment falls back to the normal methods. For + instance, if *x* is an instance of a class with an "__iadd__()" + method, "x += y" is equivalent to "x = x.__iadd__(y)" . If + "__iadd__()" does not exist, or if "x.__iadd__(y)" returns + "NotImplemented", "x.__add__(y)" and "y.__radd__(x)" are + considered, as with the evaluation of "x + y". In certain + situations, augmented assignment can result in unexpected errors + (see Why does a_tuple[i] += [‘item’] raise an exception when the + addition works?), but this behavior is in fact part of the data + model. + +object.__neg__(self) +object.__pos__(self) +object.__abs__(self) +object.__invert__(self) + + Called to implement the unary arithmetic operations ("-", "+", + "abs()" and "~"). + +object.__complex__(self) +object.__int__(self) +object.__float__(self) + + Called to implement the built-in functions "complex()", "int()" and + "float()". Should return a value of the appropriate type. + +object.__index__(self) + + Called to implement "operator.index()", and whenever Python needs + to losslessly convert the numeric object to an integer object (such + as in slicing, or in the built-in "bin()", "hex()" and "oct()" + functions). Presence of this method indicates that the numeric + object is an integer type. Must return an integer. + + If "__int__()", "__float__()" and "__complex__()" are not defined + then corresponding built-in functions "int()", "float()" and + "complex()" fall back to "__index__()". + +object.__round__(self[, ndigits]) +object.__trunc__(self) +object.__floor__(self) +object.__ceil__(self) + + Called to implement the built-in function "round()" and "math" + functions "trunc()", "floor()" and "ceil()". Unless *ndigits* is + passed to "__round__()" all these methods should return the value + of the object truncated to an "Integral" (typically an "int"). + + Changed in version 3.14: "int()" no longer delegates to the + "__trunc__()" method. +''', + 'objects': r'''Objects, values and types +************************* + +*Objects* are Python’s abstraction for data. All data in a Python +program is represented by objects or by relations between objects. (In +a sense, and in conformance to Von Neumann’s model of a “stored +program computer”, code is also represented by objects.) + +Every object has an identity, a type and a value. An object’s +*identity* never changes once it has been created; you may think of it +as the object’s address in memory. The "is" operator compares the +identity of two objects; the "id()" function returns an integer +representing its identity. + +**CPython implementation detail:** For CPython, "id(x)" is the memory +address where "x" is stored. + +An object’s type determines the operations that the object supports +(e.g., “does it have a length?”) and also defines the possible values +for objects of that type. The "type()" function returns an object’s +type (which is an object itself). Like its identity, an object’s +*type* is also unchangeable. [1] + +The *value* of some objects can change. Objects whose value can +change are said to be *mutable*; objects whose value is unchangeable +once they are created are called *immutable*. (The value of an +immutable container object that contains a reference to a mutable +object can change when the latter’s value is changed; however the +container is still considered immutable, because the collection of +objects it contains cannot be changed. So, immutability is not +strictly the same as having an unchangeable value, it is more subtle.) +An object’s mutability is determined by its type; for instance, +numbers, strings and tuples are immutable, while dictionaries and +lists are mutable. + +Objects are never explicitly destroyed; however, when they become +unreachable they may be garbage-collected. An implementation is +allowed to postpone garbage collection or omit it altogether — it is a +matter of implementation quality how garbage collection is +implemented, as long as no objects are collected that are still +reachable. + +**CPython implementation detail:** CPython currently uses a reference- +counting scheme with (optional) delayed detection of cyclically linked +garbage, which collects most objects as soon as they become +unreachable, but is not guaranteed to collect garbage containing +circular references. See the documentation of the "gc" module for +information on controlling the collection of cyclic garbage. Other +implementations act differently and CPython may change. Do not depend +on immediate finalization of objects when they become unreachable (so +you should always close files explicitly). + +Note that the use of the implementation’s tracing or debugging +facilities may keep objects alive that would normally be collectable. +Also note that catching an exception with a "try"…"except" statement +may keep objects alive. + +Some objects contain references to “external” resources such as open +files or windows. It is understood that these resources are freed +when the object is garbage-collected, but since garbage collection is +not guaranteed to happen, such objects also provide an explicit way to +release the external resource, usually a "close()" method. Programs +are strongly recommended to explicitly close such objects. The +"try"…"finally" statement and the "with" statement provide convenient +ways to do this. + +Some objects contain references to other objects; these are called +*containers*. Examples of containers are tuples, lists and +dictionaries. The references are part of a container’s value. In +most cases, when we talk about the value of a container, we imply the +values, not the identities of the contained objects; however, when we +talk about the mutability of a container, only the identities of the +immediately contained objects are implied. So, if an immutable +container (like a tuple) contains a reference to a mutable object, its +value changes if that mutable object is changed. + +Types affect almost all aspects of object behavior. Even the +importance of object identity is affected in some sense: for immutable +types, operations that compute new values may actually return a +reference to any existing object with the same type and value, while +for mutable objects this is not allowed. For example, after "a = 1; b += 1", *a* and *b* may or may not refer to the same object with the +value one, depending on the implementation. This is because "int" is +an immutable type, so the reference to "1" can be reused. This +behaviour depends on the implementation used, so should not be relied +upon, but is something to be aware of when making use of object +identity tests. However, after "c = []; d = []", *c* and *d* are +guaranteed to refer to two different, unique, newly created empty +lists. (Note that "e = f = []" assigns the *same* object to both *e* +and *f*.) +''', + 'operator-summary': r'''Operator precedence +******************* + +The following table summarizes the operator precedence in Python, from +highest precedence (most binding) to lowest precedence (least +binding). Operators in the same box have the same precedence. Unless +the syntax is explicitly given, operators are binary. Operators in +the same box group left to right (except for exponentiation and +conditional expressions, which group from right to left). + +Note that comparisons, membership tests, and identity tests, all have +the same precedence and have a left-to-right chaining feature as +described in the Comparisons section. + ++-------------------------------------------------+---------------------------------------+ +| Operator | Description | +|=================================================|=======================================| +| "(expressions...)", "[expressions...]", "{key: | Binding or parenthesized expression, | +| value...}", "{expressions...}" | list display, dictionary display, set | +| | display | ++-------------------------------------------------+---------------------------------------+ +| "x[index]", "x[index:index]", | Subscription, slicing, call, | +| "x(arguments...)", "x.attribute" | attribute reference | ++-------------------------------------------------+---------------------------------------+ +| "await x" | Await expression | ++-------------------------------------------------+---------------------------------------+ +| "**" | Exponentiation [5] | ++-------------------------------------------------+---------------------------------------+ +| "+x", "-x", "~x" | Positive, negative, bitwise NOT | ++-------------------------------------------------+---------------------------------------+ +| "*", "@", "/", "//", "%" | Multiplication, matrix | +| | multiplication, division, floor | +| | division, remainder [6] | ++-------------------------------------------------+---------------------------------------+ +| "+", "-" | Addition and subtraction | ++-------------------------------------------------+---------------------------------------+ +| "<<", ">>" | Shifts | ++-------------------------------------------------+---------------------------------------+ +| "&" | Bitwise AND | ++-------------------------------------------------+---------------------------------------+ +| "^" | Bitwise XOR | ++-------------------------------------------------+---------------------------------------+ +| "|" | Bitwise OR | ++-------------------------------------------------+---------------------------------------+ +| "in", "not in", "is", "is not", "<", "<=", ">", | Comparisons, including membership | +| ">=", "!=", "==" | tests and identity tests | ++-------------------------------------------------+---------------------------------------+ +| "not x" | Boolean NOT | ++-------------------------------------------------+---------------------------------------+ +| "and" | Boolean AND | ++-------------------------------------------------+---------------------------------------+ +| "or" | Boolean OR | ++-------------------------------------------------+---------------------------------------+ +| "if" – "else" | Conditional expression | ++-------------------------------------------------+---------------------------------------+ +| "lambda" | Lambda expression | ++-------------------------------------------------+---------------------------------------+ +| ":=" | Assignment expression | ++-------------------------------------------------+---------------------------------------+ + +-[ Footnotes ]- + +[1] While "abs(x%y) < abs(y)" is true mathematically, for floats it + may not be true numerically due to roundoff. For example, and + assuming a platform on which a Python float is an IEEE 754 double- + precision number, in order that "-1e-100 % 1e100" have the same + sign as "1e100", the computed result is "-1e-100 + 1e100", which + is numerically exactly equal to "1e100". The function + "math.fmod()" returns a result whose sign matches the sign of the + first argument instead, and so returns "-1e-100" in this case. + Which approach is more appropriate depends on the application. + +[2] If x is very close to an exact integer multiple of y, it’s + possible for "x//y" to be one larger than "(x-x%y)//y" due to + rounding. In such cases, Python returns the latter result, in + order to preserve that "divmod(x,y)[0] * y + x % y" be very close + to "x". + +[3] The Unicode standard distinguishes between *code points* (e.g. + U+0041) and *abstract characters* (e.g. “LATIN CAPITAL LETTER A”). + While most abstract characters in Unicode are only represented + using one code point, there is a number of abstract characters + that can in addition be represented using a sequence of more than + one code point. For example, the abstract character “LATIN + CAPITAL LETTER C WITH CEDILLA” can be represented as a single + *precomposed character* at code position U+00C7, or as a sequence + of a *base character* at code position U+0043 (LATIN CAPITAL + LETTER C), followed by a *combining character* at code position + U+0327 (COMBINING CEDILLA). + + The comparison operators on strings compare at the level of + Unicode code points. This may be counter-intuitive to humans. For + example, ""\u00C7" == "\u0043\u0327"" is "False", even though both + strings represent the same abstract character “LATIN CAPITAL + LETTER C WITH CEDILLA”. + + To compare strings at the level of abstract characters (that is, + in a way intuitive to humans), use "unicodedata.normalize()". + +[4] Due to automatic garbage-collection, free lists, and the dynamic + nature of descriptors, you may notice seemingly unusual behaviour + in certain uses of the "is" operator, like those involving + comparisons between instance methods, or constants. Check their + documentation for more info. + +[5] The power operator "**" binds less tightly than an arithmetic or + bitwise unary operator on its right, that is, "2**-1" is "0.5". + +[6] The "%" operator is also used for string formatting; the same + precedence applies. +''', + 'pass': r'''The "pass" statement +******************** + + pass_stmt ::= "pass" + +"pass" is a null operation — when it is executed, nothing happens. It +is useful as a placeholder when a statement is required syntactically, +but no code needs to be executed, for example: + + def f(arg): pass # a function that does nothing (yet) + + class C: pass # a class with no methods (yet) +''', + 'power': r'''The power operator +****************** + +The power operator binds more tightly than unary operators on its +left; it binds less tightly than unary operators on its right. The +syntax is: + + power ::= (await_expr | primary) ["**" u_expr] + +Thus, in an unparenthesized sequence of power and unary operators, the +operators are evaluated from right to left (this does not constrain +the evaluation order for the operands): "-1**2" results in "-1". + +The power operator has the same semantics as the built-in "pow()" +function, when called with two arguments: it yields its left argument +raised to the power of its right argument. The numeric arguments are +first converted to a common type, and the result is of that type. + +For int operands, the result has the same type as the operands unless +the second argument is negative; in that case, all arguments are +converted to float and a float result is delivered. For example, +"10**2" returns "100", but "10**-2" returns "0.01". + +Raising "0.0" to a negative power results in a "ZeroDivisionError". +Raising a negative number to a fractional power results in a "complex" +number. (In earlier versions it raised a "ValueError".) + +This operation can be customized using the special "__pow__()" and +"__rpow__()" methods. +''', + 'raise': r'''The "raise" statement +********************* + + raise_stmt ::= "raise" [expression ["from" expression]] + +If no expressions are present, "raise" re-raises the exception that is +currently being handled, which is also known as the *active +exception*. If there isn’t currently an active exception, a +"RuntimeError" exception is raised indicating that this is an error. + +Otherwise, "raise" evaluates the first expression as the exception +object. It must be either a subclass or an instance of +"BaseException". If it is a class, the exception instance will be +obtained when needed by instantiating the class with no arguments. + +The *type* of the exception is the exception instance’s class, the +*value* is the instance itself. + +A traceback object is normally created automatically when an exception +is raised and attached to it as the "__traceback__" attribute. You can +create an exception and set your own traceback in one step using the +"with_traceback()" exception method (which returns the same exception +instance, with its traceback set to its argument), like so: + + raise Exception("foo occurred").with_traceback(tracebackobj) + +The "from" clause is used for exception chaining: if given, the second +*expression* must be another exception class or instance. If the +second expression is an exception instance, it will be attached to the +raised exception as the "__cause__" attribute (which is writable). If +the expression is an exception class, the class will be instantiated +and the resulting exception instance will be attached to the raised +exception as the "__cause__" attribute. If the raised exception is not +handled, both exceptions will be printed: + + >>> try: + ... print(1 / 0) + ... except Exception as exc: + ... raise RuntimeError("Something bad happened") from exc + ... + Traceback (most recent call last): + File "<stdin>", line 2, in <module> + print(1 / 0) + ~~^~~ + ZeroDivisionError: division by zero + + The above exception was the direct cause of the following exception: + + Traceback (most recent call last): + File "<stdin>", line 4, in <module> + raise RuntimeError("Something bad happened") from exc + RuntimeError: Something bad happened + +A similar mechanism works implicitly if a new exception is raised when +an exception is already being handled. An exception may be handled +when an "except" or "finally" clause, or a "with" statement, is used. +The previous exception is then attached as the new exception’s +"__context__" attribute: + + >>> try: + ... print(1 / 0) + ... except: + ... raise RuntimeError("Something bad happened") + ... + Traceback (most recent call last): + File "<stdin>", line 2, in <module> + print(1 / 0) + ~~^~~ + ZeroDivisionError: division by zero + + During handling of the above exception, another exception occurred: + + Traceback (most recent call last): + File "<stdin>", line 4, in <module> + raise RuntimeError("Something bad happened") + RuntimeError: Something bad happened + +Exception chaining can be explicitly suppressed by specifying "None" +in the "from" clause: + + >>> try: + ... print(1 / 0) + ... except: + ... raise RuntimeError("Something bad happened") from None + ... + Traceback (most recent call last): + File "<stdin>", line 4, in <module> + RuntimeError: Something bad happened + +Additional information on exceptions can be found in section +Exceptions, and information about handling exceptions is in section +The try statement. + +Changed in version 3.3: "None" is now permitted as "Y" in "raise X +from Y".Added the "__suppress_context__" attribute to suppress +automatic display of the exception context. + +Changed in version 3.11: If the traceback of the active exception is +modified in an "except" clause, a subsequent "raise" statement re- +raises the exception with the modified traceback. Previously, the +exception was re-raised with the traceback it had when it was caught. +''', + 'return': r'''The "return" statement +********************** + + return_stmt ::= "return" [expression_list] + +"return" may only occur syntactically nested in a function definition, +not within a nested class definition. + +If an expression list is present, it is evaluated, else "None" is +substituted. + +"return" leaves the current function call with the expression list (or +"None") as return value. + +When "return" passes control out of a "try" statement with a "finally" +clause, that "finally" clause is executed before really leaving the +function. + +In a generator function, the "return" statement indicates that the +generator is done and will cause "StopIteration" to be raised. The +returned value (if any) is used as an argument to construct +"StopIteration" and becomes the "StopIteration.value" attribute. + +In an asynchronous generator function, an empty "return" statement +indicates that the asynchronous generator is done and will cause +"StopAsyncIteration" to be raised. A non-empty "return" statement is +a syntax error in an asynchronous generator function. +''', + 'sequence-types': r'''Emulating container types +************************* + +The following methods can be defined to implement container objects. +None of them are provided by the "object" class itself. Containers +usually are *sequences* (such as "lists" or "tuples") or *mappings* +(like *dictionaries*), but can represent other containers as well. +The first set of methods is used either to emulate a sequence or to +emulate a mapping; the difference is that for a sequence, the +allowable keys should be the integers *k* for which "0 <= k < N" where +*N* is the length of the sequence, or "slice" objects, which define a +range of items. It is also recommended that mappings provide the +methods "keys()", "values()", "items()", "get()", "clear()", +"setdefault()", "pop()", "popitem()", "copy()", and "update()" +behaving similar to those for Python’s standard "dictionary" objects. +The "collections.abc" module provides a "MutableMapping" *abstract +base class* to help create those methods from a base set of +"__getitem__()", "__setitem__()", "__delitem__()", and "keys()". +Mutable sequences should provide methods "append()", "count()", +"index()", "extend()", "insert()", "pop()", "remove()", "reverse()" +and "sort()", like Python standard "list" objects. Finally, sequence +types should implement addition (meaning concatenation) and +multiplication (meaning repetition) by defining the methods +"__add__()", "__radd__()", "__iadd__()", "__mul__()", "__rmul__()" and +"__imul__()" described below; they should not define other numerical +operators. It is recommended that both mappings and sequences +implement the "__contains__()" method to allow efficient use of the +"in" operator; for mappings, "in" should search the mapping’s keys; +for sequences, it should search through the values. It is further +recommended that both mappings and sequences implement the +"__iter__()" method to allow efficient iteration through the +container; for mappings, "__iter__()" should iterate through the +object’s keys; for sequences, it should iterate through the values. + +object.__len__(self) + + Called to implement the built-in function "len()". Should return + the length of the object, an integer ">=" 0. Also, an object that + doesn’t define a "__bool__()" method and whose "__len__()" method + returns zero is considered to be false in a Boolean context. + + **CPython implementation detail:** In CPython, the length is + required to be at most "sys.maxsize". If the length is larger than + "sys.maxsize" some features (such as "len()") may raise + "OverflowError". To prevent raising "OverflowError" by truth value + testing, an object must define a "__bool__()" method. + +object.__length_hint__(self) + + Called to implement "operator.length_hint()". Should return an + estimated length for the object (which may be greater or less than + the actual length). The length must be an integer ">=" 0. The + return value may also be "NotImplemented", which is treated the + same as if the "__length_hint__" method didn’t exist at all. This + method is purely an optimization and is never required for + correctness. + + Added in version 3.4. + +Note: + + Slicing is done exclusively with the following three methods. A + call like + + a[1:2] = b + + is translated to + + a[slice(1, 2, None)] = b + + and so forth. Missing slice items are always filled in with "None". + +object.__getitem__(self, key) + + Called to implement evaluation of "self[key]". For *sequence* + types, the accepted keys should be integers. Optionally, they may + support "slice" objects as well. Negative index support is also + optional. If *key* is of an inappropriate type, "TypeError" may be + raised; if *key* is a value outside the set of indexes for the + sequence (after any special interpretation of negative values), + "IndexError" should be raised. For *mapping* types, if *key* is + missing (not in the container), "KeyError" should be raised. + + Note: + + "for" loops expect that an "IndexError" will be raised for + illegal indexes to allow proper detection of the end of the + sequence. + + Note: + + When subscripting a *class*, the special class method + "__class_getitem__()" may be called instead of "__getitem__()". + See __class_getitem__ versus __getitem__ for more details. + +object.__setitem__(self, key, value) + + Called to implement assignment to "self[key]". Same note as for + "__getitem__()". This should only be implemented for mappings if + the objects support changes to the values for keys, or if new keys + can be added, or for sequences if elements can be replaced. The + same exceptions should be raised for improper *key* values as for + the "__getitem__()" method. + +object.__delitem__(self, key) + + Called to implement deletion of "self[key]". Same note as for + "__getitem__()". This should only be implemented for mappings if + the objects support removal of keys, or for sequences if elements + can be removed from the sequence. The same exceptions should be + raised for improper *key* values as for the "__getitem__()" method. + +object.__missing__(self, key) + + Called by "dict"."__getitem__()" to implement "self[key]" for dict + subclasses when key is not in the dictionary. + +object.__iter__(self) + + This method is called when an *iterator* is required for a + container. This method should return a new iterator object that can + iterate over all the objects in the container. For mappings, it + should iterate over the keys of the container. + +object.__reversed__(self) + + Called (if present) by the "reversed()" built-in to implement + reverse iteration. It should return a new iterator object that + iterates over all the objects in the container in reverse order. + + If the "__reversed__()" method is not provided, the "reversed()" + built-in will fall back to using the sequence protocol ("__len__()" + and "__getitem__()"). Objects that support the sequence protocol + should only provide "__reversed__()" if they can provide an + implementation that is more efficient than the one provided by + "reversed()". + +The membership test operators ("in" and "not in") are normally +implemented as an iteration through a container. However, container +objects can supply the following special method with a more efficient +implementation, which also does not require the object be iterable. + +object.__contains__(self, item) + + Called to implement membership test operators. Should return true + if *item* is in *self*, false otherwise. For mapping objects, this + should consider the keys of the mapping rather than the values or + the key-item pairs. + + For objects that don’t define "__contains__()", the membership test + first tries iteration via "__iter__()", then the old sequence + iteration protocol via "__getitem__()", see this section in the + language reference. +''', + 'shifting': r'''Shifting operations +******************* + +The shifting operations have lower priority than the arithmetic +operations: + + shift_expr ::= a_expr | shift_expr ("<<" | ">>") a_expr + +These operators accept integers as arguments. They shift the first +argument to the left or right by the number of bits given by the +second argument. + +The left shift operation can be customized using the special +"__lshift__()" and "__rlshift__()" methods. The right shift operation +can be customized using the special "__rshift__()" and "__rrshift__()" +methods. + +A right shift by *n* bits is defined as floor division by "pow(2,n)". +A left shift by *n* bits is defined as multiplication with "pow(2,n)". +''', + 'slicings': r'''Slicings +******** + +A slicing selects a range of items in a sequence object (e.g., a +string, tuple or list). Slicings may be used as expressions or as +targets in assignment or "del" statements. The syntax for a slicing: + + slicing ::= primary "[" slice_list "]" + slice_list ::= slice_item ("," slice_item)* [","] + slice_item ::= expression | proper_slice + proper_slice ::= [lower_bound] ":" [upper_bound] [ ":" [stride] ] + lower_bound ::= expression + upper_bound ::= expression + stride ::= expression + +There is ambiguity in the formal syntax here: anything that looks like +an expression list also looks like a slice list, so any subscription +can be interpreted as a slicing. Rather than further complicating the +syntax, this is disambiguated by defining that in this case the +interpretation as a subscription takes priority over the +interpretation as a slicing (this is the case if the slice list +contains no proper slice). + +The semantics for a slicing are as follows. The primary is indexed +(using the same "__getitem__()" method as normal subscription) with a +key that is constructed from the slice list, as follows. If the slice +list contains at least one comma, the key is a tuple containing the +conversion of the slice items; otherwise, the conversion of the lone +slice item is the key. The conversion of a slice item that is an +expression is that expression. The conversion of a proper slice is a +slice object (see section The standard type hierarchy) whose "start", +"stop" and "step" attributes are the values of the expressions given +as lower bound, upper bound and stride, respectively, substituting +"None" for missing expressions. +''', + 'specialattrs': r'''Special Attributes +****************** + +The implementation adds a few special read-only attributes to several +object types, where they are relevant. Some of these are not reported +by the "dir()" built-in function. + +definition.__name__ + + The name of the class, function, method, descriptor, or generator + instance. + +definition.__qualname__ + + The *qualified name* of the class, function, method, descriptor, or + generator instance. + + Added in version 3.3. + +definition.__module__ + + The name of the module in which a class or function was defined. + +definition.__doc__ + + The documentation string of a class or function, or "None" if + undefined. + +definition.__type_params__ + + The type parameters of generic classes, functions, and type + aliases. For classes and functions that are not generic, this will + be an empty tuple. + + Added in version 3.12. +''', + 'specialnames': r'''Special method names +******************** + +A class can implement certain operations that are invoked by special +syntax (such as arithmetic operations or subscripting and slicing) by +defining methods with special names. This is Python’s approach to +*operator overloading*, allowing classes to define their own behavior +with respect to language operators. For instance, if a class defines +a method named "__getitem__()", and "x" is an instance of this class, +then "x[i]" is roughly equivalent to "type(x).__getitem__(x, i)". +Except where mentioned, attempts to execute an operation raise an +exception when no appropriate method is defined (typically +"AttributeError" or "TypeError"). + +Setting a special method to "None" indicates that the corresponding +operation is not available. For example, if a class sets "__iter__()" +to "None", the class is not iterable, so calling "iter()" on its +instances will raise a "TypeError" (without falling back to +"__getitem__()"). [2] + +When implementing a class that emulates any built-in type, it is +important that the emulation only be implemented to the degree that it +makes sense for the object being modelled. For example, some +sequences may work well with retrieval of individual elements, but +extracting a slice may not make sense. (One example of this is the +"NodeList" interface in the W3C’s Document Object Model.) + + +Basic customization +=================== + +object.__new__(cls[, ...]) + + Called to create a new instance of class *cls*. "__new__()" is a + static method (special-cased so you need not declare it as such) + that takes the class of which an instance was requested as its + first argument. The remaining arguments are those passed to the + object constructor expression (the call to the class). The return + value of "__new__()" should be the new object instance (usually an + instance of *cls*). + + Typical implementations create a new instance of the class by + invoking the superclass’s "__new__()" method using + "super().__new__(cls[, ...])" with appropriate arguments and then + modifying the newly created instance as necessary before returning + it. + + If "__new__()" is invoked during object construction and it returns + an instance of *cls*, then the new instance’s "__init__()" method + will be invoked like "__init__(self[, ...])", where *self* is the + new instance and the remaining arguments are the same as were + passed to the object constructor. + + If "__new__()" does not return an instance of *cls*, then the new + instance’s "__init__()" method will not be invoked. + + "__new__()" is intended mainly to allow subclasses of immutable + types (like int, str, or tuple) to customize instance creation. It + is also commonly overridden in custom metaclasses in order to + customize class creation. + +object.__init__(self[, ...]) + + Called after the instance has been created (by "__new__()"), but + before it is returned to the caller. The arguments are those + passed to the class constructor expression. If a base class has an + "__init__()" method, the derived class’s "__init__()" method, if + any, must explicitly call it to ensure proper initialization of the + base class part of the instance; for example: + "super().__init__([args...])". + + Because "__new__()" and "__init__()" work together in constructing + objects ("__new__()" to create it, and "__init__()" to customize + it), no non-"None" value may be returned by "__init__()"; doing so + will cause a "TypeError" to be raised at runtime. + +object.__del__(self) + + Called when the instance is about to be destroyed. This is also + called a finalizer or (improperly) a destructor. If a base class + has a "__del__()" method, the derived class’s "__del__()" method, + if any, must explicitly call it to ensure proper deletion of the + base class part of the instance. + + It is possible (though not recommended!) for the "__del__()" method + to postpone destruction of the instance by creating a new reference + to it. This is called object *resurrection*. It is + implementation-dependent whether "__del__()" is called a second + time when a resurrected object is about to be destroyed; the + current *CPython* implementation only calls it once. + + It is not guaranteed that "__del__()" methods are called for + objects that still exist when the interpreter exits. + "weakref.finalize" provides a straightforward way to register a + cleanup function to be called when an object is garbage collected. + + Note: + + "del x" doesn’t directly call "x.__del__()" — the former + decrements the reference count for "x" by one, and the latter is + only called when "x"’s reference count reaches zero. + + **CPython implementation detail:** It is possible for a reference + cycle to prevent the reference count of an object from going to + zero. In this case, the cycle will be later detected and deleted + by the *cyclic garbage collector*. A common cause of reference + cycles is when an exception has been caught in a local variable. + The frame’s locals then reference the exception, which references + its own traceback, which references the locals of all frames caught + in the traceback. + + See also: Documentation for the "gc" module. + + Warning: + + Due to the precarious circumstances under which "__del__()" + methods are invoked, exceptions that occur during their execution + are ignored, and a warning is printed to "sys.stderr" instead. + In particular: + + * "__del__()" can be invoked when arbitrary code is being + executed, including from any arbitrary thread. If "__del__()" + needs to take a lock or invoke any other blocking resource, it + may deadlock as the resource may already be taken by the code + that gets interrupted to execute "__del__()". + + * "__del__()" can be executed during interpreter shutdown. As a + consequence, the global variables it needs to access (including + other modules) may already have been deleted or set to "None". + Python guarantees that globals whose name begins with a single + underscore are deleted from their module before other globals + are deleted; if no other references to such globals exist, this + may help in assuring that imported modules are still available + at the time when the "__del__()" method is called. + +object.__repr__(self) + + Called by the "repr()" built-in function to compute the “official” + string representation of an object. If at all possible, this + should look like a valid Python expression that could be used to + recreate an object with the same value (given an appropriate + environment). If this is not possible, a string of the form + "<...some useful description...>" should be returned. The return + value must be a string object. If a class defines "__repr__()" but + not "__str__()", then "__repr__()" is also used when an “informal” + string representation of instances of that class is required. + + This is typically used for debugging, so it is important that the + representation is information-rich and unambiguous. A default + implementation is provided by the "object" class itself. + +object.__str__(self) + + Called by "str(object)", the default "__format__()" implementation, + and the built-in function "print()", to compute the “informal” or + nicely printable string representation of an object. The return + value must be a str object. + + This method differs from "object.__repr__()" in that there is no + expectation that "__str__()" return a valid Python expression: a + more convenient or concise representation can be used. + + The default implementation defined by the built-in type "object" + calls "object.__repr__()". + +object.__bytes__(self) + + Called by bytes to compute a byte-string representation of an + object. This should return a "bytes" object. The "object" class + itself does not provide this method. + +object.__format__(self, format_spec) + + Called by the "format()" built-in function, and by extension, + evaluation of formatted string literals and the "str.format()" + method, to produce a “formatted” string representation of an + object. The *format_spec* argument is a string that contains a + description of the formatting options desired. The interpretation + of the *format_spec* argument is up to the type implementing + "__format__()", however most classes will either delegate + formatting to one of the built-in types, or use a similar + formatting option syntax. + + See Format Specification Mini-Language for a description of the + standard formatting syntax. + + The return value must be a string object. + + The default implementation by the "object" class should be given an + empty *format_spec* string. It delegates to "__str__()". + + Changed in version 3.4: The __format__ method of "object" itself + raises a "TypeError" if passed any non-empty string. + + Changed in version 3.7: "object.__format__(x, '')" is now + equivalent to "str(x)" rather than "format(str(x), '')". + +object.__lt__(self, other) +object.__le__(self, other) +object.__eq__(self, other) +object.__ne__(self, other) +object.__gt__(self, other) +object.__ge__(self, other) + + These are the so-called “rich comparison” methods. The + correspondence between operator symbols and method names is as + follows: "x<y" calls "x.__lt__(y)", "x<=y" calls "x.__le__(y)", + "x==y" calls "x.__eq__(y)", "x!=y" calls "x.__ne__(y)", "x>y" calls + "x.__gt__(y)", and "x>=y" calls "x.__ge__(y)". + + A rich comparison method may return the singleton "NotImplemented" + if it does not implement the operation for a given pair of + arguments. By convention, "False" and "True" are returned for a + successful comparison. However, these methods can return any value, + so if the comparison operator is used in a Boolean context (e.g., + in the condition of an "if" statement), Python will call "bool()" + on the value to determine if the result is true or false. + + By default, "object" implements "__eq__()" by using "is", returning + "NotImplemented" in the case of a false comparison: "True if x is y + else NotImplemented". For "__ne__()", by default it delegates to + "__eq__()" and inverts the result unless it is "NotImplemented". + There are no other implied relationships among the comparison + operators or default implementations; for example, the truth of + "(x<y or x==y)" does not imply "x<=y". To automatically generate + ordering operations from a single root operation, see + "functools.total_ordering()". + + By default, the "object" class provides implementations consistent + with Value comparisons: equality compares according to object + identity, and order comparisons raise "TypeError". Each default + method may generate these results directly, but may also return + "NotImplemented". + + See the paragraph on "__hash__()" for some important notes on + creating *hashable* objects which support custom comparison + operations and are usable as dictionary keys. + + There are no swapped-argument versions of these methods (to be used + when the left argument does not support the operation but the right + argument does); rather, "__lt__()" and "__gt__()" are each other’s + reflection, "__le__()" and "__ge__()" are each other’s reflection, + and "__eq__()" and "__ne__()" are their own reflection. If the + operands are of different types, and the right operand’s type is a + direct or indirect subclass of the left operand’s type, the + reflected method of the right operand has priority, otherwise the + left operand’s method has priority. Virtual subclassing is not + considered. + + When no appropriate method returns any value other than + "NotImplemented", the "==" and "!=" operators will fall back to + "is" and "is not", respectively. + +object.__hash__(self) + + Called by built-in function "hash()" and for operations on members + of hashed collections including "set", "frozenset", and "dict". + The "__hash__()" method should return an integer. The only required + property is that objects which compare equal have the same hash + value; it is advised to mix together the hash values of the + components of the object that also play a part in comparison of + objects by packing them into a tuple and hashing the tuple. + Example: + + def __hash__(self): + return hash((self.name, self.nick, self.color)) + + Note: + + "hash()" truncates the value returned from an object’s custom + "__hash__()" method to the size of a "Py_ssize_t". This is + typically 8 bytes on 64-bit builds and 4 bytes on 32-bit builds. + If an object’s "__hash__()" must interoperate on builds of + different bit sizes, be sure to check the width on all supported + builds. An easy way to do this is with "python -c "import sys; + print(sys.hash_info.width)"". + + If a class does not define an "__eq__()" method it should not + define a "__hash__()" operation either; if it defines "__eq__()" + but not "__hash__()", its instances will not be usable as items in + hashable collections. If a class defines mutable objects and + implements an "__eq__()" method, it should not implement + "__hash__()", since the implementation of *hashable* collections + requires that a key’s hash value is immutable (if the object’s hash + value changes, it will be in the wrong hash bucket). + + User-defined classes have "__eq__()" and "__hash__()" methods by + default (inherited from the "object" class); with them, all objects + compare unequal (except with themselves) and "x.__hash__()" returns + an appropriate value such that "x == y" implies both that "x is y" + and "hash(x) == hash(y)". + + A class that overrides "__eq__()" and does not define "__hash__()" + will have its "__hash__()" implicitly set to "None". When the + "__hash__()" method of a class is "None", instances of the class + will raise an appropriate "TypeError" when a program attempts to + retrieve their hash value, and will also be correctly identified as + unhashable when checking "isinstance(obj, + collections.abc.Hashable)". + + If a class that overrides "__eq__()" needs to retain the + implementation of "__hash__()" from a parent class, the interpreter + must be told this explicitly by setting "__hash__ = + <ParentClass>.__hash__". + + If a class that does not override "__eq__()" wishes to suppress + hash support, it should include "__hash__ = None" in the class + definition. A class which defines its own "__hash__()" that + explicitly raises a "TypeError" would be incorrectly identified as + hashable by an "isinstance(obj, collections.abc.Hashable)" call. + + Note: + + By default, the "__hash__()" values of str and bytes objects are + “salted” with an unpredictable random value. Although they + remain constant within an individual Python process, they are not + predictable between repeated invocations of Python.This is + intended to provide protection against a denial-of-service caused + by carefully chosen inputs that exploit the worst case + performance of a dict insertion, *O*(*n*^2) complexity. See + http://ocert.org/advisories/ocert-2011-003.html for + details.Changing hash values affects the iteration order of sets. + Python has never made guarantees about this ordering (and it + typically varies between 32-bit and 64-bit builds).See also + "PYTHONHASHSEED". + + Changed in version 3.3: Hash randomization is enabled by default. + +object.__bool__(self) + + Called to implement truth value testing and the built-in operation + "bool()"; should return "False" or "True". When this method is not + defined, "__len__()" is called, if it is defined, and the object is + considered true if its result is nonzero. If a class defines + neither "__len__()" nor "__bool__()" (which is true of the "object" + class itself), all its instances are considered true. + + +Customizing attribute access +============================ + +The following methods can be defined to customize the meaning of +attribute access (use of, assignment to, or deletion of "x.name") for +class instances. + +object.__getattr__(self, name) + + Called when the default attribute access fails with an + "AttributeError" (either "__getattribute__()" raises an + "AttributeError" because *name* is not an instance attribute or an + attribute in the class tree for "self"; or "__get__()" of a *name* + property raises "AttributeError"). This method should either + return the (computed) attribute value or raise an "AttributeError" + exception. The "object" class itself does not provide this method. + + Note that if the attribute is found through the normal mechanism, + "__getattr__()" is not called. (This is an intentional asymmetry + between "__getattr__()" and "__setattr__()".) This is done both for + efficiency reasons and because otherwise "__getattr__()" would have + no way to access other attributes of the instance. Note that at + least for instance variables, you can take total control by not + inserting any values in the instance attribute dictionary (but + instead inserting them in another object). See the + "__getattribute__()" method below for a way to actually get total + control over attribute access. + +object.__getattribute__(self, name) + + Called unconditionally to implement attribute accesses for + instances of the class. If the class also defines "__getattr__()", + the latter will not be called unless "__getattribute__()" either + calls it explicitly or raises an "AttributeError". This method + should return the (computed) attribute value or raise an + "AttributeError" exception. In order to avoid infinite recursion in + this method, its implementation should always call the base class + method with the same name to access any attributes it needs, for + example, "object.__getattribute__(self, name)". + + Note: + + This method may still be bypassed when looking up special methods + as the result of implicit invocation via language syntax or + built-in functions. See Special method lookup. + + For certain sensitive attribute accesses, raises an auditing event + "object.__getattr__" with arguments "obj" and "name". + +object.__setattr__(self, name, value) + + Called when an attribute assignment is attempted. This is called + instead of the normal mechanism (i.e. store the value in the + instance dictionary). *name* is the attribute name, *value* is the + value to be assigned to it. + + If "__setattr__()" wants to assign to an instance attribute, it + should call the base class method with the same name, for example, + "object.__setattr__(self, name, value)". + + For certain sensitive attribute assignments, raises an auditing + event "object.__setattr__" with arguments "obj", "name", "value". + +object.__delattr__(self, name) + + Like "__setattr__()" but for attribute deletion instead of + assignment. This should only be implemented if "del obj.name" is + meaningful for the object. + + For certain sensitive attribute deletions, raises an auditing event + "object.__delattr__" with arguments "obj" and "name". + +object.__dir__(self) + + Called when "dir()" is called on the object. An iterable must be + returned. "dir()" converts the returned iterable to a list and + sorts it. + + +Customizing module attribute access +----------------------------------- + +Special names "__getattr__" and "__dir__" can be also used to +customize access to module attributes. The "__getattr__" function at +the module level should accept one argument which is the name of an +attribute and return the computed value or raise an "AttributeError". +If an attribute is not found on a module object through the normal +lookup, i.e. "object.__getattribute__()", then "__getattr__" is +searched in the module "__dict__" before raising an "AttributeError". +If found, it is called with the attribute name and the result is +returned. + +The "__dir__" function should accept no arguments, and return an +iterable of strings that represents the names accessible on module. If +present, this function overrides the standard "dir()" search on a +module. + +For a more fine grained customization of the module behavior (setting +attributes, properties, etc.), one can set the "__class__" attribute +of a module object to a subclass of "types.ModuleType". For example: + + import sys + from types import ModuleType + + class VerboseModule(ModuleType): + def __repr__(self): + return f'Verbose {self.__name__}' + + def __setattr__(self, attr, value): + print(f'Setting {attr}...') + super().__setattr__(attr, value) + + sys.modules[__name__].__class__ = VerboseModule + +Note: + + Defining module "__getattr__" and setting module "__class__" only + affect lookups made using the attribute access syntax – directly + accessing the module globals (whether by code within the module, or + via a reference to the module’s globals dictionary) is unaffected. + +Changed in version 3.5: "__class__" module attribute is now writable. + +Added in version 3.7: "__getattr__" and "__dir__" module attributes. + +See also: + + **PEP 562** - Module __getattr__ and __dir__ + Describes the "__getattr__" and "__dir__" functions on modules. + + +Implementing Descriptors +------------------------ + +The following methods only apply when an instance of the class +containing the method (a so-called *descriptor* class) appears in an +*owner* class (the descriptor must be in either the owner’s class +dictionary or in the class dictionary for one of its parents). In the +examples below, “the attribute” refers to the attribute whose name is +the key of the property in the owner class’ "__dict__". The "object" +class itself does not implement any of these protocols. + +object.__get__(self, instance, owner=None) + + Called to get the attribute of the owner class (class attribute + access) or of an instance of that class (instance attribute + access). The optional *owner* argument is the owner class, while + *instance* is the instance that the attribute was accessed through, + or "None" when the attribute is accessed through the *owner*. + + This method should return the computed attribute value or raise an + "AttributeError" exception. + + **PEP 252** specifies that "__get__()" is callable with one or two + arguments. Python’s own built-in descriptors support this + specification; however, it is likely that some third-party tools + have descriptors that require both arguments. Python’s own + "__getattribute__()" implementation always passes in both arguments + whether they are required or not. + +object.__set__(self, instance, value) + + Called to set the attribute on an instance *instance* of the owner + class to a new value, *value*. + + Note, adding "__set__()" or "__delete__()" changes the kind of + descriptor to a “data descriptor”. See Invoking Descriptors for + more details. + +object.__delete__(self, instance) + + Called to delete the attribute on an instance *instance* of the + owner class. + +Instances of descriptors may also have the "__objclass__" attribute +present: + +object.__objclass__ + + The attribute "__objclass__" is interpreted by the "inspect" module + as specifying the class where this object was defined (setting this + appropriately can assist in runtime introspection of dynamic class + attributes). For callables, it may indicate that an instance of the + given type (or a subclass) is expected or required as the first + positional argument (for example, CPython sets this attribute for + unbound methods that are implemented in C). + + +Invoking Descriptors +-------------------- + +In general, a descriptor is an object attribute with “binding +behavior”, one whose attribute access has been overridden by methods +in the descriptor protocol: "__get__()", "__set__()", and +"__delete__()". If any of those methods are defined for an object, it +is said to be a descriptor. + +The default behavior for attribute access is to get, set, or delete +the attribute from an object’s dictionary. For instance, "a.x" has a +lookup chain starting with "a.__dict__['x']", then +"type(a).__dict__['x']", and continuing through the base classes of +"type(a)" excluding metaclasses. + +However, if the looked-up value is an object defining one of the +descriptor methods, then Python may override the default behavior and +invoke the descriptor method instead. Where this occurs in the +precedence chain depends on which descriptor methods were defined and +how they were called. + +The starting point for descriptor invocation is a binding, "a.x". How +the arguments are assembled depends on "a": + +Direct Call + The simplest and least common call is when user code directly + invokes a descriptor method: "x.__get__(a)". + +Instance Binding + If binding to an object instance, "a.x" is transformed into the + call: "type(a).__dict__['x'].__get__(a, type(a))". + +Class Binding + If binding to a class, "A.x" is transformed into the call: + "A.__dict__['x'].__get__(None, A)". + +Super Binding + A dotted lookup such as "super(A, a).x" searches + "a.__class__.__mro__" for a base class "B" following "A" and then + returns "B.__dict__['x'].__get__(a, A)". If not a descriptor, "x" + is returned unchanged. + +For instance bindings, the precedence of descriptor invocation depends +on which descriptor methods are defined. A descriptor can define any +combination of "__get__()", "__set__()" and "__delete__()". If it +does not define "__get__()", then accessing the attribute will return +the descriptor object itself unless there is a value in the object’s +instance dictionary. If the descriptor defines "__set__()" and/or +"__delete__()", it is a data descriptor; if it defines neither, it is +a non-data descriptor. Normally, data descriptors define both +"__get__()" and "__set__()", while non-data descriptors have just the +"__get__()" method. Data descriptors with "__get__()" and "__set__()" +(and/or "__delete__()") defined always override a redefinition in an +instance dictionary. In contrast, non-data descriptors can be +overridden by instances. + +Python methods (including those decorated with "@staticmethod" and +"@classmethod") are implemented as non-data descriptors. Accordingly, +instances can redefine and override methods. This allows individual +instances to acquire behaviors that differ from other instances of the +same class. + +The "property()" function is implemented as a data descriptor. +Accordingly, instances cannot override the behavior of a property. + + +__slots__ +--------- + +*__slots__* allow us to explicitly declare data members (like +properties) and deny the creation of "__dict__" and *__weakref__* +(unless explicitly declared in *__slots__* or available in a parent.) + +The space saved over using "__dict__" can be significant. Attribute +lookup speed can be significantly improved as well. + +object.__slots__ + + This class variable can be assigned a string, iterable, or sequence + of strings with variable names used by instances. *__slots__* + reserves space for the declared variables and prevents the + automatic creation of "__dict__" and *__weakref__* for each + instance. + +Notes on using *__slots__*: + +* When inheriting from a class without *__slots__*, the "__dict__" and + *__weakref__* attribute of the instances will always be accessible. + +* Without a "__dict__" variable, instances cannot be assigned new + variables not listed in the *__slots__* definition. Attempts to + assign to an unlisted variable name raises "AttributeError". If + dynamic assignment of new variables is desired, then add + "'__dict__'" to the sequence of strings in the *__slots__* + declaration. + +* Without a *__weakref__* variable for each instance, classes defining + *__slots__* do not support "weak references" to its instances. If + weak reference support is needed, then add "'__weakref__'" to the + sequence of strings in the *__slots__* declaration. + +* *__slots__* are implemented at the class level by creating + descriptors for each variable name. As a result, class attributes + cannot be used to set default values for instance variables defined + by *__slots__*; otherwise, the class attribute would overwrite the + descriptor assignment. + +* The action of a *__slots__* declaration is not limited to the class + where it is defined. *__slots__* declared in parents are available + in child classes. However, instances of a child subclass will get a + "__dict__" and *__weakref__* unless the subclass also defines + *__slots__* (which should only contain names of any *additional* + slots). + +* If a class defines a slot also defined in a base class, the instance + variable defined by the base class slot is inaccessible (except by + retrieving its descriptor directly from the base class). This + renders the meaning of the program undefined. In the future, a + check may be added to prevent this. + +* "TypeError" will be raised if nonempty *__slots__* are defined for a + class derived from a ""variable-length" built-in type" such as + "int", "bytes", and "tuple". + +* Any non-string *iterable* may be assigned to *__slots__*. + +* If a "dictionary" is used to assign *__slots__*, the dictionary keys + will be used as the slot names. The values of the dictionary can be + used to provide per-attribute docstrings that will be recognised by + "inspect.getdoc()" and displayed in the output of "help()". + +* "__class__" assignment works only if both classes have the same + *__slots__*. + +* Multiple inheritance with multiple slotted parent classes can be + used, but only one parent is allowed to have attributes created by + slots (the other bases must have empty slot layouts) - violations + raise "TypeError". + +* If an *iterator* is used for *__slots__* then a *descriptor* is + created for each of the iterator’s values. However, the *__slots__* + attribute will be an empty iterator. + + +Customizing class creation +========================== + +Whenever a class inherits from another class, "__init_subclass__()" is +called on the parent class. This way, it is possible to write classes +which change the behavior of subclasses. This is closely related to +class decorators, but where class decorators only affect the specific +class they’re applied to, "__init_subclass__" solely applies to future +subclasses of the class defining the method. + +classmethod object.__init_subclass__(cls) + + This method is called whenever the containing class is subclassed. + *cls* is then the new subclass. If defined as a normal instance + method, this method is implicitly converted to a class method. + + Keyword arguments which are given to a new class are passed to the + parent class’s "__init_subclass__". For compatibility with other + classes using "__init_subclass__", one should take out the needed + keyword arguments and pass the others over to the base class, as + in: + + class Philosopher: + def __init_subclass__(cls, /, default_name, **kwargs): + super().__init_subclass__(**kwargs) + cls.default_name = default_name + + class AustralianPhilosopher(Philosopher, default_name="Bruce"): + pass + + The default implementation "object.__init_subclass__" does nothing, + but raises an error if it is called with any arguments. + + Note: + + The metaclass hint "metaclass" is consumed by the rest of the + type machinery, and is never passed to "__init_subclass__" + implementations. The actual metaclass (rather than the explicit + hint) can be accessed as "type(cls)". + + Added in version 3.6. + +When a class is created, "type.__new__()" scans the class variables +and makes callbacks to those with a "__set_name__()" hook. + +object.__set_name__(self, owner, name) + + Automatically called at the time the owning class *owner* is + created. The object has been assigned to *name* in that class: + + class A: + x = C() # Automatically calls: x.__set_name__(A, 'x') + + If the class variable is assigned after the class is created, + "__set_name__()" will not be called automatically. If needed, + "__set_name__()" can be called directly: + + class A: + pass + + c = C() + A.x = c # The hook is not called + c.__set_name__(A, 'x') # Manually invoke the hook + + See Creating the class object for more details. + + Added in version 3.6. + + +Metaclasses +----------- + +By default, classes are constructed using "type()". The class body is +executed in a new namespace and the class name is bound locally to the +result of "type(name, bases, namespace)". + +The class creation process can be customized by passing the +"metaclass" keyword argument in the class definition line, or by +inheriting from an existing class that included such an argument. In +the following example, both "MyClass" and "MySubclass" are instances +of "Meta": + + class Meta(type): + pass + + class MyClass(metaclass=Meta): + pass + + class MySubclass(MyClass): + pass + +Any other keyword arguments that are specified in the class definition +are passed through to all metaclass operations described below. + +When a class definition is executed, the following steps occur: + +* MRO entries are resolved; + +* the appropriate metaclass is determined; + +* the class namespace is prepared; + +* the class body is executed; + +* the class object is created. + + +Resolving MRO entries +--------------------- + +object.__mro_entries__(self, bases) + + If a base that appears in a class definition is not an instance of + "type", then an "__mro_entries__()" method is searched on the base. + If an "__mro_entries__()" method is found, the base is substituted + with the result of a call to "__mro_entries__()" when creating the + class. The method is called with the original bases tuple passed to + the *bases* parameter, and must return a tuple of classes that will + be used instead of the base. The returned tuple may be empty: in + these cases, the original base is ignored. + +See also: + + "types.resolve_bases()" + Dynamically resolve bases that are not instances of "type". + + "types.get_original_bases()" + Retrieve a class’s “original bases” prior to modifications by + "__mro_entries__()". + + **PEP 560** + Core support for typing module and generic types. + + +Determining the appropriate metaclass +------------------------------------- + +The appropriate metaclass for a class definition is determined as +follows: + +* if no bases and no explicit metaclass are given, then "type()" is + used; + +* if an explicit metaclass is given and it is *not* an instance of + "type()", then it is used directly as the metaclass; + +* if an instance of "type()" is given as the explicit metaclass, or + bases are defined, then the most derived metaclass is used. + +The most derived metaclass is selected from the explicitly specified +metaclass (if any) and the metaclasses (i.e. "type(cls)") of all +specified base classes. The most derived metaclass is one which is a +subtype of *all* of these candidate metaclasses. If none of the +candidate metaclasses meets that criterion, then the class definition +will fail with "TypeError". + + +Preparing the class namespace +----------------------------- + +Once the appropriate metaclass has been identified, then the class +namespace is prepared. If the metaclass has a "__prepare__" attribute, +it is called as "namespace = metaclass.__prepare__(name, bases, +**kwds)" (where the additional keyword arguments, if any, come from +the class definition). The "__prepare__" method should be implemented +as a "classmethod". The namespace returned by "__prepare__" is passed +in to "__new__", but when the final class object is created the +namespace is copied into a new "dict". + +If the metaclass has no "__prepare__" attribute, then the class +namespace is initialised as an empty ordered mapping. + +See also: + + **PEP 3115** - Metaclasses in Python 3000 + Introduced the "__prepare__" namespace hook + + +Executing the class body +------------------------ + +The class body is executed (approximately) as "exec(body, globals(), +namespace)". The key difference from a normal call to "exec()" is that +lexical scoping allows the class body (including any methods) to +reference names from the current and outer scopes when the class +definition occurs inside a function. + +However, even when the class definition occurs inside the function, +methods defined inside the class still cannot see names defined at the +class scope. Class variables must be accessed through the first +parameter of instance or class methods, or through the implicit +lexically scoped "__class__" reference described in the next section. + + +Creating the class object +------------------------- + +Once the class namespace has been populated by executing the class +body, the class object is created by calling "metaclass(name, bases, +namespace, **kwds)" (the additional keywords passed here are the same +as those passed to "__prepare__"). + +This class object is the one that will be referenced by the zero- +argument form of "super()". "__class__" is an implicit closure +reference created by the compiler if any methods in a class body refer +to either "__class__" or "super". This allows the zero argument form +of "super()" to correctly identify the class being defined based on +lexical scoping, while the class or instance that was used to make the +current call is identified based on the first argument passed to the +method. + +**CPython implementation detail:** In CPython 3.6 and later, the +"__class__" cell is passed to the metaclass as a "__classcell__" entry +in the class namespace. If present, this must be propagated up to the +"type.__new__" call in order for the class to be initialised +correctly. Failing to do so will result in a "RuntimeError" in Python +3.8. + +When using the default metaclass "type", or any metaclass that +ultimately calls "type.__new__", the following additional +customization steps are invoked after creating the class object: + +1. The "type.__new__" method collects all of the attributes in the + class namespace that define a "__set_name__()" method; + +2. Those "__set_name__" methods are called with the class being + defined and the assigned name of that particular attribute; + +3. The "__init_subclass__()" hook is called on the immediate parent of + the new class in its method resolution order. + +After the class object is created, it is passed to the class +decorators included in the class definition (if any) and the resulting +object is bound in the local namespace as the defined class. + +When a new class is created by "type.__new__", the object provided as +the namespace parameter is copied to a new ordered mapping and the +original object is discarded. The new copy is wrapped in a read-only +proxy, which becomes the "__dict__" attribute of the class object. + +See also: + + **PEP 3135** - New super + Describes the implicit "__class__" closure reference + + +Uses for metaclasses +-------------------- + +The potential uses for metaclasses are boundless. Some ideas that have +been explored include enum, logging, interface checking, automatic +delegation, automatic property creation, proxies, frameworks, and +automatic resource locking/synchronization. + + +Customizing instance and subclass checks +======================================== + +The following methods are used to override the default behavior of the +"isinstance()" and "issubclass()" built-in functions. + +In particular, the metaclass "abc.ABCMeta" implements these methods in +order to allow the addition of Abstract Base Classes (ABCs) as +“virtual base classes” to any class or type (including built-in +types), including other ABCs. + +type.__instancecheck__(self, instance) + + Return true if *instance* should be considered a (direct or + indirect) instance of *class*. If defined, called to implement + "isinstance(instance, class)". + +type.__subclasscheck__(self, subclass) + + Return true if *subclass* should be considered a (direct or + indirect) subclass of *class*. If defined, called to implement + "issubclass(subclass, class)". + +Note that these methods are looked up on the type (metaclass) of a +class. They cannot be defined as class methods in the actual class. +This is consistent with the lookup of special methods that are called +on instances, only in this case the instance is itself a class. + +See also: + + **PEP 3119** - Introducing Abstract Base Classes + Includes the specification for customizing "isinstance()" and + "issubclass()" behavior through "__instancecheck__()" and + "__subclasscheck__()", with motivation for this functionality in + the context of adding Abstract Base Classes (see the "abc" + module) to the language. + + +Emulating generic types +======================= + +When using *type annotations*, it is often useful to *parameterize* a +*generic type* using Python’s square-brackets notation. For example, +the annotation "list[int]" might be used to signify a "list" in which +all the elements are of type "int". + +See also: + + **PEP 484** - Type Hints + Introducing Python’s framework for type annotations + + Generic Alias Types + Documentation for objects representing parameterized generic + classes + + Generics, user-defined generics and "typing.Generic" + Documentation on how to implement generic classes that can be + parameterized at runtime and understood by static type-checkers. + +A class can *generally* only be parameterized if it defines the +special class method "__class_getitem__()". + +classmethod object.__class_getitem__(cls, key) + + Return an object representing the specialization of a generic class + by type arguments found in *key*. + + When defined on a class, "__class_getitem__()" is automatically a + class method. As such, there is no need for it to be decorated with + "@classmethod" when it is defined. + + +The purpose of *__class_getitem__* +---------------------------------- + +The purpose of "__class_getitem__()" is to allow runtime +parameterization of standard-library generic classes in order to more +easily apply *type hints* to these classes. + +To implement custom generic classes that can be parameterized at +runtime and understood by static type-checkers, users should either +inherit from a standard library class that already implements +"__class_getitem__()", or inherit from "typing.Generic", which has its +own implementation of "__class_getitem__()". + +Custom implementations of "__class_getitem__()" on classes defined +outside of the standard library may not be understood by third-party +type-checkers such as mypy. Using "__class_getitem__()" on any class +for purposes other than type hinting is discouraged. + + +*__class_getitem__* versus *__getitem__* +---------------------------------------- + +Usually, the subscription of an object using square brackets will call +the "__getitem__()" instance method defined on the object’s class. +However, if the object being subscribed is itself a class, the class +method "__class_getitem__()" may be called instead. +"__class_getitem__()" should return a GenericAlias object if it is +properly defined. + +Presented with the *expression* "obj[x]", the Python interpreter +follows something like the following process to decide whether +"__getitem__()" or "__class_getitem__()" should be called: + + from inspect import isclass + + def subscribe(obj, x): + """Return the result of the expression 'obj[x]'""" + + class_of_obj = type(obj) + + # If the class of obj defines __getitem__, + # call class_of_obj.__getitem__(obj, x) + if hasattr(class_of_obj, '__getitem__'): + return class_of_obj.__getitem__(obj, x) + + # Else, if obj is a class and defines __class_getitem__, + # call obj.__class_getitem__(x) + elif isclass(obj) and hasattr(obj, '__class_getitem__'): + return obj.__class_getitem__(x) + + # Else, raise an exception + else: + raise TypeError( + f"'{class_of_obj.__name__}' object is not subscriptable" + ) + +In Python, all classes are themselves instances of other classes. The +class of a class is known as that class’s *metaclass*, and most +classes have the "type" class as their metaclass. "type" does not +define "__getitem__()", meaning that expressions such as "list[int]", +"dict[str, float]" and "tuple[str, bytes]" all result in +"__class_getitem__()" being called: + + >>> # list has class "type" as its metaclass, like most classes: + >>> type(list) + <class 'type'> + >>> type(dict) == type(list) == type(tuple) == type(str) == type(bytes) + True + >>> # "list[int]" calls "list.__class_getitem__(int)" + >>> list[int] + list[int] + >>> # list.__class_getitem__ returns a GenericAlias object: + >>> type(list[int]) + <class 'types.GenericAlias'> + +However, if a class has a custom metaclass that defines +"__getitem__()", subscribing the class may result in different +behaviour. An example of this can be found in the "enum" module: + + >>> from enum import Enum + >>> class Menu(Enum): + ... """A breakfast menu""" + ... SPAM = 'spam' + ... BACON = 'bacon' + ... + >>> # Enum classes have a custom metaclass: + >>> type(Menu) + <class 'enum.EnumMeta'> + >>> # EnumMeta defines __getitem__, + >>> # so __class_getitem__ is not called, + >>> # and the result is not a GenericAlias object: + >>> Menu['SPAM'] + <Menu.SPAM: 'spam'> + >>> type(Menu['SPAM']) + <enum 'Menu'> + +See also: + + **PEP 560** - Core Support for typing module and generic types + Introducing "__class_getitem__()", and outlining when a + subscription results in "__class_getitem__()" being called + instead of "__getitem__()" + + +Emulating callable objects +========================== + +object.__call__(self[, args...]) + + Called when the instance is “called” as a function; if this method + is defined, "x(arg1, arg2, ...)" roughly translates to + "type(x).__call__(x, arg1, ...)". The "object" class itself does + not provide this method. + + +Emulating container types +========================= + +The following methods can be defined to implement container objects. +None of them are provided by the "object" class itself. Containers +usually are *sequences* (such as "lists" or "tuples") or *mappings* +(like *dictionaries*), but can represent other containers as well. +The first set of methods is used either to emulate a sequence or to +emulate a mapping; the difference is that for a sequence, the +allowable keys should be the integers *k* for which "0 <= k < N" where +*N* is the length of the sequence, or "slice" objects, which define a +range of items. It is also recommended that mappings provide the +methods "keys()", "values()", "items()", "get()", "clear()", +"setdefault()", "pop()", "popitem()", "copy()", and "update()" +behaving similar to those for Python’s standard "dictionary" objects. +The "collections.abc" module provides a "MutableMapping" *abstract +base class* to help create those methods from a base set of +"__getitem__()", "__setitem__()", "__delitem__()", and "keys()". +Mutable sequences should provide methods "append()", "count()", +"index()", "extend()", "insert()", "pop()", "remove()", "reverse()" +and "sort()", like Python standard "list" objects. Finally, sequence +types should implement addition (meaning concatenation) and +multiplication (meaning repetition) by defining the methods +"__add__()", "__radd__()", "__iadd__()", "__mul__()", "__rmul__()" and +"__imul__()" described below; they should not define other numerical +operators. It is recommended that both mappings and sequences +implement the "__contains__()" method to allow efficient use of the +"in" operator; for mappings, "in" should search the mapping’s keys; +for sequences, it should search through the values. It is further +recommended that both mappings and sequences implement the +"__iter__()" method to allow efficient iteration through the +container; for mappings, "__iter__()" should iterate through the +object’s keys; for sequences, it should iterate through the values. + +object.__len__(self) + + Called to implement the built-in function "len()". Should return + the length of the object, an integer ">=" 0. Also, an object that + doesn’t define a "__bool__()" method and whose "__len__()" method + returns zero is considered to be false in a Boolean context. + + **CPython implementation detail:** In CPython, the length is + required to be at most "sys.maxsize". If the length is larger than + "sys.maxsize" some features (such as "len()") may raise + "OverflowError". To prevent raising "OverflowError" by truth value + testing, an object must define a "__bool__()" method. + +object.__length_hint__(self) + + Called to implement "operator.length_hint()". Should return an + estimated length for the object (which may be greater or less than + the actual length). The length must be an integer ">=" 0. The + return value may also be "NotImplemented", which is treated the + same as if the "__length_hint__" method didn’t exist at all. This + method is purely an optimization and is never required for + correctness. + + Added in version 3.4. + +Note: + + Slicing is done exclusively with the following three methods. A + call like + + a[1:2] = b + + is translated to + + a[slice(1, 2, None)] = b + + and so forth. Missing slice items are always filled in with "None". + +object.__getitem__(self, key) + + Called to implement evaluation of "self[key]". For *sequence* + types, the accepted keys should be integers. Optionally, they may + support "slice" objects as well. Negative index support is also + optional. If *key* is of an inappropriate type, "TypeError" may be + raised; if *key* is a value outside the set of indexes for the + sequence (after any special interpretation of negative values), + "IndexError" should be raised. For *mapping* types, if *key* is + missing (not in the container), "KeyError" should be raised. + + Note: + + "for" loops expect that an "IndexError" will be raised for + illegal indexes to allow proper detection of the end of the + sequence. + + Note: + + When subscripting a *class*, the special class method + "__class_getitem__()" may be called instead of "__getitem__()". + See __class_getitem__ versus __getitem__ for more details. + +object.__setitem__(self, key, value) + + Called to implement assignment to "self[key]". Same note as for + "__getitem__()". This should only be implemented for mappings if + the objects support changes to the values for keys, or if new keys + can be added, or for sequences if elements can be replaced. The + same exceptions should be raised for improper *key* values as for + the "__getitem__()" method. + +object.__delitem__(self, key) + + Called to implement deletion of "self[key]". Same note as for + "__getitem__()". This should only be implemented for mappings if + the objects support removal of keys, or for sequences if elements + can be removed from the sequence. The same exceptions should be + raised for improper *key* values as for the "__getitem__()" method. + +object.__missing__(self, key) + + Called by "dict"."__getitem__()" to implement "self[key]" for dict + subclasses when key is not in the dictionary. + +object.__iter__(self) + + This method is called when an *iterator* is required for a + container. This method should return a new iterator object that can + iterate over all the objects in the container. For mappings, it + should iterate over the keys of the container. + +object.__reversed__(self) + + Called (if present) by the "reversed()" built-in to implement + reverse iteration. It should return a new iterator object that + iterates over all the objects in the container in reverse order. + + If the "__reversed__()" method is not provided, the "reversed()" + built-in will fall back to using the sequence protocol ("__len__()" + and "__getitem__()"). Objects that support the sequence protocol + should only provide "__reversed__()" if they can provide an + implementation that is more efficient than the one provided by + "reversed()". + +The membership test operators ("in" and "not in") are normally +implemented as an iteration through a container. However, container +objects can supply the following special method with a more efficient +implementation, which also does not require the object be iterable. + +object.__contains__(self, item) + + Called to implement membership test operators. Should return true + if *item* is in *self*, false otherwise. For mapping objects, this + should consider the keys of the mapping rather than the values or + the key-item pairs. + + For objects that don’t define "__contains__()", the membership test + first tries iteration via "__iter__()", then the old sequence + iteration protocol via "__getitem__()", see this section in the + language reference. + + +Emulating numeric types +======================= + +The following methods can be defined to emulate numeric objects. +Methods corresponding to operations that are not supported by the +particular kind of number implemented (e.g., bitwise operations for +non-integral numbers) should be left undefined. + +object.__add__(self, other) +object.__sub__(self, other) +object.__mul__(self, other) +object.__matmul__(self, other) +object.__truediv__(self, other) +object.__floordiv__(self, other) +object.__mod__(self, other) +object.__divmod__(self, other) +object.__pow__(self, other[, modulo]) +object.__lshift__(self, other) +object.__rshift__(self, other) +object.__and__(self, other) +object.__xor__(self, other) +object.__or__(self, other) + + These methods are called to implement the binary arithmetic + operations ("+", "-", "*", "@", "/", "//", "%", "divmod()", + "pow()", "**", "<<", ">>", "&", "^", "|"). For instance, to + evaluate the expression "x + y", where *x* is an instance of a + class that has an "__add__()" method, "type(x).__add__(x, y)" is + called. The "__divmod__()" method should be the equivalent to + using "__floordiv__()" and "__mod__()"; it should not be related to + "__truediv__()". Note that "__pow__()" should be defined to accept + an optional third argument if the ternary version of the built-in + "pow()" function is to be supported. + + If one of those methods does not support the operation with the + supplied arguments, it should return "NotImplemented". + +object.__radd__(self, other) +object.__rsub__(self, other) +object.__rmul__(self, other) +object.__rmatmul__(self, other) +object.__rtruediv__(self, other) +object.__rfloordiv__(self, other) +object.__rmod__(self, other) +object.__rdivmod__(self, other) +object.__rpow__(self, other[, modulo]) +object.__rlshift__(self, other) +object.__rrshift__(self, other) +object.__rand__(self, other) +object.__rxor__(self, other) +object.__ror__(self, other) + + These methods are called to implement the binary arithmetic + operations ("+", "-", "*", "@", "/", "//", "%", "divmod()", + "pow()", "**", "<<", ">>", "&", "^", "|") with reflected (swapped) + operands. These functions are only called if the operands are of + different types, when the left operand does not support the + corresponding operation [3], or the right operand’s class is + derived from the left operand’s class. [4] For instance, to + evaluate the expression "x - y", where *y* is an instance of a + class that has an "__rsub__()" method, "type(y).__rsub__(y, x)" is + called if "type(x).__sub__(x, y)" returns "NotImplemented" or + "type(y)" is a subclass of "type(x)". [5] + + Note that ternary "pow()" will not try calling "__rpow__()" (the + coercion rules would become too complicated). + + Note: + + If the right operand’s type is a subclass of the left operand’s + type and that subclass provides a different implementation of the + reflected method for the operation, this method will be called + before the left operand’s non-reflected method. This behavior + allows subclasses to override their ancestors’ operations. + +object.__iadd__(self, other) +object.__isub__(self, other) +object.__imul__(self, other) +object.__imatmul__(self, other) +object.__itruediv__(self, other) +object.__ifloordiv__(self, other) +object.__imod__(self, other) +object.__ipow__(self, other[, modulo]) +object.__ilshift__(self, other) +object.__irshift__(self, other) +object.__iand__(self, other) +object.__ixor__(self, other) +object.__ior__(self, other) + + These methods are called to implement the augmented arithmetic + assignments ("+=", "-=", "*=", "@=", "/=", "//=", "%=", "**=", + "<<=", ">>=", "&=", "^=", "|="). These methods should attempt to + do the operation in-place (modifying *self*) and return the result + (which could be, but does not have to be, *self*). If a specific + method is not defined, or if that method returns "NotImplemented", + the augmented assignment falls back to the normal methods. For + instance, if *x* is an instance of a class with an "__iadd__()" + method, "x += y" is equivalent to "x = x.__iadd__(y)" . If + "__iadd__()" does not exist, or if "x.__iadd__(y)" returns + "NotImplemented", "x.__add__(y)" and "y.__radd__(x)" are + considered, as with the evaluation of "x + y". In certain + situations, augmented assignment can result in unexpected errors + (see Why does a_tuple[i] += [‘item’] raise an exception when the + addition works?), but this behavior is in fact part of the data + model. + +object.__neg__(self) +object.__pos__(self) +object.__abs__(self) +object.__invert__(self) + + Called to implement the unary arithmetic operations ("-", "+", + "abs()" and "~"). + +object.__complex__(self) +object.__int__(self) +object.__float__(self) + + Called to implement the built-in functions "complex()", "int()" and + "float()". Should return a value of the appropriate type. + +object.__index__(self) + + Called to implement "operator.index()", and whenever Python needs + to losslessly convert the numeric object to an integer object (such + as in slicing, or in the built-in "bin()", "hex()" and "oct()" + functions). Presence of this method indicates that the numeric + object is an integer type. Must return an integer. + + If "__int__()", "__float__()" and "__complex__()" are not defined + then corresponding built-in functions "int()", "float()" and + "complex()" fall back to "__index__()". + +object.__round__(self[, ndigits]) +object.__trunc__(self) +object.__floor__(self) +object.__ceil__(self) + + Called to implement the built-in function "round()" and "math" + functions "trunc()", "floor()" and "ceil()". Unless *ndigits* is + passed to "__round__()" all these methods should return the value + of the object truncated to an "Integral" (typically an "int"). + + Changed in version 3.14: "int()" no longer delegates to the + "__trunc__()" method. + + +With Statement Context Managers +=============================== + +A *context manager* is an object that defines the runtime context to +be established when executing a "with" statement. The context manager +handles the entry into, and the exit from, the desired runtime context +for the execution of the block of code. Context managers are normally +invoked using the "with" statement (described in section The with +statement), but can also be used by directly invoking their methods. + +Typical uses of context managers include saving and restoring various +kinds of global state, locking and unlocking resources, closing opened +files, etc. + +For more information on context managers, see Context Manager Types. +The "object" class itself does not provide the context manager +methods. + +object.__enter__(self) + + Enter the runtime context related to this object. The "with" + statement will bind this method’s return value to the target(s) + specified in the "as" clause of the statement, if any. + +object.__exit__(self, exc_type, exc_value, traceback) + + Exit the runtime context related to this object. The parameters + describe the exception that caused the context to be exited. If the + context was exited without an exception, all three arguments will + be "None". + + If an exception is supplied, and the method wishes to suppress the + exception (i.e., prevent it from being propagated), it should + return a true value. Otherwise, the exception will be processed + normally upon exit from this method. + + Note that "__exit__()" methods should not reraise the passed-in + exception; this is the caller’s responsibility. + +See also: + + **PEP 343** - The “with” statement + The specification, background, and examples for the Python "with" + statement. + + +Customizing positional arguments in class pattern matching +========================================================== + +When using a class name in a pattern, positional arguments in the +pattern are not allowed by default, i.e. "case MyClass(x, y)" is +typically invalid without special support in "MyClass". To be able to +use that kind of pattern, the class needs to define a *__match_args__* +attribute. + +object.__match_args__ + + This class variable can be assigned a tuple of strings. When this + class is used in a class pattern with positional arguments, each + positional argument will be converted into a keyword argument, + using the corresponding value in *__match_args__* as the keyword. + The absence of this attribute is equivalent to setting it to "()". + +For example, if "MyClass.__match_args__" is "("left", "center", +"right")" that means that "case MyClass(x, y)" is equivalent to "case +MyClass(left=x, center=y)". Note that the number of arguments in the +pattern must be smaller than or equal to the number of elements in +*__match_args__*; if it is larger, the pattern match attempt will +raise a "TypeError". + +Added in version 3.10. + +See also: + + **PEP 634** - Structural Pattern Matching + The specification for the Python "match" statement. + + +Emulating buffer types +====================== + +The buffer protocol provides a way for Python objects to expose +efficient access to a low-level memory array. This protocol is +implemented by builtin types such as "bytes" and "memoryview", and +third-party libraries may define additional buffer types. + +While buffer types are usually implemented in C, it is also possible +to implement the protocol in Python. + +object.__buffer__(self, flags) + + Called when a buffer is requested from *self* (for example, by the + "memoryview" constructor). The *flags* argument is an integer + representing the kind of buffer requested, affecting for example + whether the returned buffer is read-only or writable. + "inspect.BufferFlags" provides a convenient way to interpret the + flags. The method must return a "memoryview" object. + +object.__release_buffer__(self, buffer) + + Called when a buffer is no longer needed. The *buffer* argument is + a "memoryview" object that was previously returned by + "__buffer__()". The method must release any resources associated + with the buffer. This method should return "None". Buffer objects + that do not need to perform any cleanup are not required to + implement this method. + +Added in version 3.12. + +See also: + + **PEP 688** - Making the buffer protocol accessible in Python + Introduces the Python "__buffer__" and "__release_buffer__" + methods. + + "collections.abc.Buffer" + ABC for buffer types. + + +Annotations +=========== + +Functions, classes, and modules may contain *annotations*, which are a +way to associate information (usually *type hints*) with a symbol. + +object.__annotations__ + + This attribute contains the annotations for an object. It is lazily + evaluated, so accessing the attribute may execute arbitrary code + and raise exceptions. If evaluation is successful, the attribute is + set to a dictionary mapping from variable names to annotations. + + Changed in version 3.14: Annotations are now lazily evaluated. + +object.__annotate__(format) + + An *annotate function*. Returns a new dictionary object mapping + attribute/parameter names to their annotation values. + + Takes a format parameter specifying the format in which annotations + values should be provided. It must be a member of the + "annotationlib.Format" enum, or an integer with a value + corresponding to a member of the enum. + + If an annotate function doesn’t support the requested format, it + must raise "NotImplementedError". Annotate functions must always + support "VALUE" format; they must not raise "NotImplementedError()" + when called with this format. + + When called with "VALUE" format, an annotate function may raise + "NameError"; it must not raise "NameError" when called requesting + any other format. + + If an object does not have any annotations, "__annotate__" should + preferably be set to "None" (it can’t be deleted), rather than set + to a function that returns an empty dict. + + Added in version 3.14. + +See also: + + **PEP 649** — Deferred evaluation of annotation using descriptors + Introduces lazy evaluation of annotations and the "__annotate__" + function. + + +Special method lookup +===================== + +For custom classes, implicit invocations of special methods are only +guaranteed to work correctly if defined on an object’s type, not in +the object’s instance dictionary. That behaviour is the reason why +the following code raises an exception: + + >>> class C: + ... pass + ... + >>> c = C() + >>> c.__len__ = lambda: 5 + >>> len(c) + Traceback (most recent call last): + File "<stdin>", line 1, in <module> + TypeError: object of type 'C' has no len() + +The rationale behind this behaviour lies with a number of special +methods such as "__hash__()" and "__repr__()" that are implemented by +all objects, including type objects. If the implicit lookup of these +methods used the conventional lookup process, they would fail when +invoked on the type object itself: + + >>> 1 .__hash__() == hash(1) + True + >>> int.__hash__() == hash(int) + Traceback (most recent call last): + File "<stdin>", line 1, in <module> + TypeError: descriptor '__hash__' of 'int' object needs an argument + +Incorrectly attempting to invoke an unbound method of a class in this +way is sometimes referred to as ‘metaclass confusion’, and is avoided +by bypassing the instance when looking up special methods: + + >>> type(1).__hash__(1) == hash(1) + True + >>> type(int).__hash__(int) == hash(int) + True + +In addition to bypassing any instance attributes in the interest of +correctness, implicit special method lookup generally also bypasses +the "__getattribute__()" method even of the object’s metaclass: + + >>> class Meta(type): + ... def __getattribute__(*args): + ... print("Metaclass getattribute invoked") + ... return type.__getattribute__(*args) + ... + >>> class C(object, metaclass=Meta): + ... def __len__(self): + ... return 10 + ... def __getattribute__(*args): + ... print("Class getattribute invoked") + ... return object.__getattribute__(*args) + ... + >>> c = C() + >>> c.__len__() # Explicit lookup via instance + Class getattribute invoked + 10 + >>> type(c).__len__(c) # Explicit lookup via type + Metaclass getattribute invoked + 10 + >>> len(c) # Implicit lookup + 10 + +Bypassing the "__getattribute__()" machinery in this fashion provides +significant scope for speed optimisations within the interpreter, at +the cost of some flexibility in the handling of special methods (the +special method *must* be set on the class object itself in order to be +consistently invoked by the interpreter). +''', + 'string-methods': r'''String Methods +************** + +Strings implement all of the common sequence operations, along with +the additional methods described below. + +Strings also support two styles of string formatting, one providing a +large degree of flexibility and customization (see "str.format()", +Format String Syntax and Custom String Formatting) and the other based +on C "printf" style formatting that handles a narrower range of types +and is slightly harder to use correctly, but is often faster for the +cases it can handle (printf-style String Formatting). + +The Text Processing Services section of the standard library covers a +number of other modules that provide various text related utilities +(including regular expression support in the "re" module). + +str.capitalize() + + Return a copy of the string with its first character capitalized + and the rest lowercased. + + Changed in version 3.8: The first character is now put into + titlecase rather than uppercase. This means that characters like + digraphs will only have their first letter capitalized, instead of + the full character. + +str.casefold() + + Return a casefolded copy of the string. Casefolded strings may be + used for caseless matching. + + Casefolding is similar to lowercasing but more aggressive because + it is intended to remove all case distinctions in a string. For + example, the German lowercase letter "'ß'" is equivalent to ""ss"". + Since it is already lowercase, "lower()" would do nothing to "'ß'"; + "casefold()" converts it to ""ss"". + + The casefolding algorithm is described in section 3.13 ‘Default + Case Folding’ of the Unicode Standard. + + Added in version 3.3. + +str.center(width[, fillchar]) + + Return centered in a string of length *width*. Padding is done + using the specified *fillchar* (default is an ASCII space). The + original string is returned if *width* is less than or equal to + "len(s)". + +str.count(sub[, start[, end]]) + + Return the number of non-overlapping occurrences of substring *sub* + in the range [*start*, *end*]. Optional arguments *start* and + *end* are interpreted as in slice notation. + + If *sub* is empty, returns the number of empty strings between + characters which is the length of the string plus one. + +str.encode(encoding='utf-8', errors='strict') + + Return the string encoded to "bytes". + + *encoding* defaults to "'utf-8'"; see Standard Encodings for + possible values. + + *errors* controls how encoding errors are handled. If "'strict'" + (the default), a "UnicodeError" exception is raised. Other possible + values are "'ignore'", "'replace'", "'xmlcharrefreplace'", + "'backslashreplace'" and any other name registered via + "codecs.register_error()". See Error Handlers for details. + + For performance reasons, the value of *errors* is not checked for + validity unless an encoding error actually occurs, Python + Development Mode is enabled or a debug build is used. + + Changed in version 3.1: Added support for keyword arguments. + + Changed in version 3.9: The value of the *errors* argument is now + checked in Python Development Mode and in debug mode. + +str.endswith(suffix[, start[, end]]) + + Return "True" if the string ends with the specified *suffix*, + otherwise return "False". *suffix* can also be a tuple of suffixes + to look for. With optional *start*, test beginning at that + position. With optional *end*, stop comparing at that position. + +str.expandtabs(tabsize=8) + + Return a copy of the string where all tab characters are replaced + by one or more spaces, depending on the current column and the + given tab size. Tab positions occur every *tabsize* characters + (default is 8, giving tab positions at columns 0, 8, 16 and so on). + To expand the string, the current column is set to zero and the + string is examined character by character. If the character is a + tab ("\t"), one or more space characters are inserted in the result + until the current column is equal to the next tab position. (The + tab character itself is not copied.) If the character is a newline + ("\n") or return ("\r"), it is copied and the current column is + reset to zero. Any other character is copied unchanged and the + current column is incremented by one regardless of how the + character is represented when printed. + + >>> '01\t012\t0123\t01234'.expandtabs() + '01 012 0123 01234' + >>> '01\t012\t0123\t01234'.expandtabs(4) + '01 012 0123 01234' + +str.find(sub[, start[, end]]) + + Return the lowest index in the string where substring *sub* is + found within the slice "s[start:end]". Optional arguments *start* + and *end* are interpreted as in slice notation. Return "-1" if + *sub* is not found. + + Note: + + The "find()" method should be used only if you need to know the + position of *sub*. To check if *sub* is a substring or not, use + the "in" operator: + + >>> 'Py' in 'Python' + True + +str.format(*args, **kwargs) + + Perform a string formatting operation. The string on which this + method is called can contain literal text or replacement fields + delimited by braces "{}". Each replacement field contains either + the numeric index of a positional argument, or the name of a + keyword argument. Returns a copy of the string where each + replacement field is replaced with the string value of the + corresponding argument. + + >>> "The sum of 1 + 2 is {0}".format(1+2) + 'The sum of 1 + 2 is 3' + + See Format String Syntax for a description of the various + formatting options that can be specified in format strings. + + Note: + + When formatting a number ("int", "float", "complex", + "decimal.Decimal" and subclasses) with the "n" type (ex: + "'{:n}'.format(1234)"), the function temporarily sets the + "LC_CTYPE" locale to the "LC_NUMERIC" locale to decode + "decimal_point" and "thousands_sep" fields of "localeconv()" if + they are non-ASCII or longer than 1 byte, and the "LC_NUMERIC" + locale is different than the "LC_CTYPE" locale. This temporary + change affects other threads. + + Changed in version 3.7: When formatting a number with the "n" type, + the function sets temporarily the "LC_CTYPE" locale to the + "LC_NUMERIC" locale in some cases. + +str.format_map(mapping, /) + + Similar to "str.format(**mapping)", except that "mapping" is used + directly and not copied to a "dict". This is useful if for example + "mapping" is a dict subclass: + + >>> class Default(dict): + ... def __missing__(self, key): + ... return key + ... + >>> '{name} was born in {country}'.format_map(Default(name='Guido')) + 'Guido was born in country' + + Added in version 3.2. + +str.index(sub[, start[, end]]) + + Like "find()", but raise "ValueError" when the substring is not + found. + +str.isalnum() + + Return "True" if all characters in the string are alphanumeric and + there is at least one character, "False" otherwise. A character + "c" is alphanumeric if one of the following returns "True": + "c.isalpha()", "c.isdecimal()", "c.isdigit()", or "c.isnumeric()". + +str.isalpha() + + Return "True" if all characters in the string are alphabetic and + there is at least one character, "False" otherwise. Alphabetic + characters are those characters defined in the Unicode character + database as “Letter”, i.e., those with general category property + being one of “Lm”, “Lt”, “Lu”, “Ll”, or “Lo”. Note that this is + different from the Alphabetic property defined in the section 4.10 + ‘Letters, Alphabetic, and Ideographic’ of the Unicode Standard. + +str.isascii() + + Return "True" if the string is empty or all characters in the + string are ASCII, "False" otherwise. ASCII characters have code + points in the range U+0000-U+007F. + + Added in version 3.7. + +str.isdecimal() + + Return "True" if all characters in the string are decimal + characters and there is at least one character, "False" otherwise. + Decimal characters are those that can be used to form numbers in + base 10, e.g. U+0660, ARABIC-INDIC DIGIT ZERO. Formally a decimal + character is a character in the Unicode General Category “Nd”. + +str.isdigit() + + Return "True" if all characters in the string are digits and there + is at least one character, "False" otherwise. Digits include + decimal characters and digits that need special handling, such as + the compatibility superscript digits. This covers digits which + cannot be used to form numbers in base 10, like the Kharosthi + numbers. Formally, a digit is a character that has the property + value Numeric_Type=Digit or Numeric_Type=Decimal. + +str.isidentifier() + + Return "True" if the string is a valid identifier according to the + language definition, section Identifiers and keywords. + + "keyword.iskeyword()" can be used to test whether string "s" is a + reserved identifier, such as "def" and "class". + + Example: + + >>> from keyword import iskeyword + + >>> 'hello'.isidentifier(), iskeyword('hello') + (True, False) + >>> 'def'.isidentifier(), iskeyword('def') + (True, True) + +str.islower() + + Return "True" if all cased characters [4] in the string are + lowercase and there is at least one cased character, "False" + otherwise. + +str.isnumeric() + + Return "True" if all characters in the string are numeric + characters, and there is at least one character, "False" otherwise. + Numeric characters include digit characters, and all characters + that have the Unicode numeric value property, e.g. U+2155, VULGAR + FRACTION ONE FIFTH. Formally, numeric characters are those with + the property value Numeric_Type=Digit, Numeric_Type=Decimal or + Numeric_Type=Numeric. + +str.isprintable() + + Return "True" if all characters in the string are printable or the + string is empty, "False" otherwise. Nonprintable characters are + those characters defined in the Unicode character database as + “Other” or “Separator”, excepting the ASCII space (0x20) which is + considered printable. (Note that printable characters in this + context are those which should not be escaped when "repr()" is + invoked on a string. It has no bearing on the handling of strings + written to "sys.stdout" or "sys.stderr".) + +str.isspace() + + Return "True" if there are only whitespace characters in the string + and there is at least one character, "False" otherwise. + + A character is *whitespace* if in the Unicode character database + (see "unicodedata"), either its general category is "Zs" + (“Separator, space”), or its bidirectional class is one of "WS", + "B", or "S". + +str.istitle() + + Return "True" if the string is a titlecased string and there is at + least one character, for example uppercase characters may only + follow uncased characters and lowercase characters only cased ones. + Return "False" otherwise. + +str.isupper() + + Return "True" if all cased characters [4] in the string are + uppercase and there is at least one cased character, "False" + otherwise. + + >>> 'BANANA'.isupper() + True + >>> 'banana'.isupper() + False + >>> 'baNana'.isupper() + False + >>> ' '.isupper() + False + +str.join(iterable) + + Return a string which is the concatenation of the strings in + *iterable*. A "TypeError" will be raised if there are any non- + string values in *iterable*, including "bytes" objects. The + separator between elements is the string providing this method. + +str.ljust(width[, fillchar]) + + Return the string left justified in a string of length *width*. + Padding is done using the specified *fillchar* (default is an ASCII + space). The original string is returned if *width* is less than or + equal to "len(s)". + +str.lower() + + Return a copy of the string with all the cased characters [4] + converted to lowercase. + + The lowercasing algorithm used is described in section 3.13 + ‘Default Case Folding’ of the Unicode Standard. + +str.lstrip([chars]) + + Return a copy of the string with leading characters removed. The + *chars* argument is a string specifying the set of characters to be + removed. If omitted or "None", the *chars* argument defaults to + removing whitespace. The *chars* argument is not a prefix; rather, + all combinations of its values are stripped: + + >>> ' spacious '.lstrip() + 'spacious ' + >>> 'www.example.com'.lstrip('cmowz.') + 'example.com' + + See "str.removeprefix()" for a method that will remove a single + prefix string rather than all of a set of characters. For example: + + >>> 'Arthur: three!'.lstrip('Arthur: ') + 'ee!' + >>> 'Arthur: three!'.removeprefix('Arthur: ') + 'three!' + +static str.maketrans(x[, y[, z]]) + + This static method returns a translation table usable for + "str.translate()". + + If there is only one argument, it must be a dictionary mapping + Unicode ordinals (integers) or characters (strings of length 1) to + Unicode ordinals, strings (of arbitrary lengths) or "None". + Character keys will then be converted to ordinals. + + If there are two arguments, they must be strings of equal length, + and in the resulting dictionary, each character in x will be mapped + to the character at the same position in y. If there is a third + argument, it must be a string, whose characters will be mapped to + "None" in the result. + +str.partition(sep) + + Split the string at the first occurrence of *sep*, and return a + 3-tuple containing the part before the separator, the separator + itself, and the part after the separator. If the separator is not + found, return a 3-tuple containing the string itself, followed by + two empty strings. + +str.removeprefix(prefix, /) + + If the string starts with the *prefix* string, return + "string[len(prefix):]". Otherwise, return a copy of the original + string: + + >>> 'TestHook'.removeprefix('Test') + 'Hook' + >>> 'BaseTestCase'.removeprefix('Test') + 'BaseTestCase' + + Added in version 3.9. + +str.removesuffix(suffix, /) + + If the string ends with the *suffix* string and that *suffix* is + not empty, return "string[:-len(suffix)]". Otherwise, return a copy + of the original string: + + >>> 'MiscTests'.removesuffix('Tests') + 'Misc' + >>> 'TmpDirMixin'.removesuffix('Tests') + 'TmpDirMixin' + + Added in version 3.9. + +str.replace(old, new, count=-1) + + Return a copy of the string with all occurrences of substring *old* + replaced by *new*. If *count* is given, only the first *count* + occurrences are replaced. If *count* is not specified or "-1", then + all occurrences are replaced. + + Changed in version 3.13: *count* is now supported as a keyword + argument. + +str.rfind(sub[, start[, end]]) + + Return the highest index in the string where substring *sub* is + found, such that *sub* is contained within "s[start:end]". + Optional arguments *start* and *end* are interpreted as in slice + notation. Return "-1" on failure. + +str.rindex(sub[, start[, end]]) + + Like "rfind()" but raises "ValueError" when the substring *sub* is + not found. + +str.rjust(width[, fillchar]) + + Return the string right justified in a string of length *width*. + Padding is done using the specified *fillchar* (default is an ASCII + space). The original string is returned if *width* is less than or + equal to "len(s)". + +str.rpartition(sep) + + Split the string at the last occurrence of *sep*, and return a + 3-tuple containing the part before the separator, the separator + itself, and the part after the separator. If the separator is not + found, return a 3-tuple containing two empty strings, followed by + the string itself. + +str.rsplit(sep=None, maxsplit=-1) + + Return a list of the words in the string, using *sep* as the + delimiter string. If *maxsplit* is given, at most *maxsplit* splits + are done, the *rightmost* ones. If *sep* is not specified or + "None", any whitespace string is a separator. Except for splitting + from the right, "rsplit()" behaves like "split()" which is + described in detail below. + +str.rstrip([chars]) + + Return a copy of the string with trailing characters removed. The + *chars* argument is a string specifying the set of characters to be + removed. If omitted or "None", the *chars* argument defaults to + removing whitespace. The *chars* argument is not a suffix; rather, + all combinations of its values are stripped: + + >>> ' spacious '.rstrip() + ' spacious' + >>> 'mississippi'.rstrip('ipz') + 'mississ' + + See "str.removesuffix()" for a method that will remove a single + suffix string rather than all of a set of characters. For example: + + >>> 'Monty Python'.rstrip(' Python') + 'M' + >>> 'Monty Python'.removesuffix(' Python') + 'Monty' + +str.split(sep=None, maxsplit=-1) + + Return a list of the words in the string, using *sep* as the + delimiter string. If *maxsplit* is given, at most *maxsplit* + splits are done (thus, the list will have at most "maxsplit+1" + elements). If *maxsplit* is not specified or "-1", then there is + no limit on the number of splits (all possible splits are made). + + If *sep* is given, consecutive delimiters are not grouped together + and are deemed to delimit empty strings (for example, + "'1,,2'.split(',')" returns "['1', '', '2']"). The *sep* argument + may consist of multiple characters as a single delimiter (to split + with multiple delimiters, use "re.split()"). Splitting an empty + string with a specified separator returns "['']". + + For example: + + >>> '1,2,3'.split(',') + ['1', '2', '3'] + >>> '1,2,3'.split(',', maxsplit=1) + ['1', '2,3'] + >>> '1,2,,3,'.split(',') + ['1', '2', '', '3', ''] + >>> '1<>2<>3<4'.split('<>') + ['1', '2', '3<4'] + + If *sep* is not specified or is "None", a different splitting + algorithm is applied: runs of consecutive whitespace are regarded + as a single separator, and the result will contain no empty strings + at the start or end if the string has leading or trailing + whitespace. Consequently, splitting an empty string or a string + consisting of just whitespace with a "None" separator returns "[]". + + For example: + + >>> '1 2 3'.split() + ['1', '2', '3'] + >>> '1 2 3'.split(maxsplit=1) + ['1', '2 3'] + >>> ' 1 2 3 '.split() + ['1', '2', '3'] + +str.splitlines(keepends=False) + + Return a list of the lines in the string, breaking at line + boundaries. Line breaks are not included in the resulting list + unless *keepends* is given and true. + + This method splits on the following line boundaries. In + particular, the boundaries are a superset of *universal newlines*. + + +-------------------------+-------------------------------+ + | Representation | Description | + |=========================|===============================| + | "\n" | Line Feed | + +-------------------------+-------------------------------+ + | "\r" | Carriage Return | + +-------------------------+-------------------------------+ + | "\r\n" | Carriage Return + Line Feed | + +-------------------------+-------------------------------+ + | "\v" or "\x0b" | Line Tabulation | + +-------------------------+-------------------------------+ + | "\f" or "\x0c" | Form Feed | + +-------------------------+-------------------------------+ + | "\x1c" | File Separator | + +-------------------------+-------------------------------+ + | "\x1d" | Group Separator | + +-------------------------+-------------------------------+ + | "\x1e" | Record Separator | + +-------------------------+-------------------------------+ + | "\x85" | Next Line (C1 Control Code) | + +-------------------------+-------------------------------+ + | "\u2028" | Line Separator | + +-------------------------+-------------------------------+ + | "\u2029" | Paragraph Separator | + +-------------------------+-------------------------------+ + + Changed in version 3.2: "\v" and "\f" added to list of line + boundaries. + + For example: + + >>> 'ab c\n\nde fg\rkl\r\n'.splitlines() + ['ab c', '', 'de fg', 'kl'] + >>> 'ab c\n\nde fg\rkl\r\n'.splitlines(keepends=True) + ['ab c\n', '\n', 'de fg\r', 'kl\r\n'] + + Unlike "split()" when a delimiter string *sep* is given, this + method returns an empty list for the empty string, and a terminal + line break does not result in an extra line: + + >>> "".splitlines() + [] + >>> "One line\n".splitlines() + ['One line'] + + For comparison, "split('\n')" gives: + + >>> ''.split('\n') + [''] + >>> 'Two lines\n'.split('\n') + ['Two lines', ''] + +str.startswith(prefix[, start[, end]]) + + Return "True" if string starts with the *prefix*, otherwise return + "False". *prefix* can also be a tuple of prefixes to look for. + With optional *start*, test string beginning at that position. + With optional *end*, stop comparing string at that position. + +str.strip([chars]) + + Return a copy of the string with the leading and trailing + characters removed. The *chars* argument is a string specifying the + set of characters to be removed. If omitted or "None", the *chars* + argument defaults to removing whitespace. The *chars* argument is + not a prefix or suffix; rather, all combinations of its values are + stripped: + + >>> ' spacious '.strip() + 'spacious' + >>> 'www.example.com'.strip('cmowz.') + 'example' + + The outermost leading and trailing *chars* argument values are + stripped from the string. Characters are removed from the leading + end until reaching a string character that is not contained in the + set of characters in *chars*. A similar action takes place on the + trailing end. For example: + + >>> comment_string = '#....... Section 3.2.1 Issue #32 .......' + >>> comment_string.strip('.#! ') + 'Section 3.2.1 Issue #32' + +str.swapcase() + + Return a copy of the string with uppercase characters converted to + lowercase and vice versa. Note that it is not necessarily true that + "s.swapcase().swapcase() == s". + +str.title() + + Return a titlecased version of the string where words start with an + uppercase character and the remaining characters are lowercase. + + For example: + + >>> 'Hello world'.title() + 'Hello World' + + The algorithm uses a simple language-independent definition of a + word as groups of consecutive letters. The definition works in + many contexts but it means that apostrophes in contractions and + possessives form word boundaries, which may not be the desired + result: + + >>> "they're bill's friends from the UK".title() + "They'Re Bill'S Friends From The Uk" + + The "string.capwords()" function does not have this problem, as it + splits words on spaces only. + + Alternatively, a workaround for apostrophes can be constructed + using regular expressions: + + >>> import re + >>> def titlecase(s): + ... return re.sub(r"[A-Za-z]+('[A-Za-z]+)?", + ... lambda mo: mo.group(0).capitalize(), + ... s) + ... + >>> titlecase("they're bill's friends.") + "They're Bill's Friends." + +str.translate(table) + + Return a copy of the string in which each character has been mapped + through the given translation table. The table must be an object + that implements indexing via "__getitem__()", typically a *mapping* + or *sequence*. When indexed by a Unicode ordinal (an integer), the + table object can do any of the following: return a Unicode ordinal + or a string, to map the character to one or more other characters; + return "None", to delete the character from the return string; or + raise a "LookupError" exception, to map the character to itself. + + You can use "str.maketrans()" to create a translation map from + character-to-character mappings in different formats. + + See also the "codecs" module for a more flexible approach to custom + character mappings. + +str.upper() + + Return a copy of the string with all the cased characters [4] + converted to uppercase. Note that "s.upper().isupper()" might be + "False" if "s" contains uncased characters or if the Unicode + category of the resulting character(s) is not “Lu” (Letter, + uppercase), but e.g. “Lt” (Letter, titlecase). + + The uppercasing algorithm used is described in section 3.13 + ‘Default Case Folding’ of the Unicode Standard. + +str.zfill(width) + + Return a copy of the string left filled with ASCII "'0'" digits to + make a string of length *width*. A leading sign prefix + ("'+'"/"'-'") is handled by inserting the padding *after* the sign + character rather than before. The original string is returned if + *width* is less than or equal to "len(s)". + + For example: + + >>> "42".zfill(5) + '00042' + >>> "-42".zfill(5) + '-0042' +''', + 'strings': '''String and Bytes literals +************************* + +String literals are described by the following lexical definitions: + + stringliteral ::= [stringprefix](shortstring | longstring) + stringprefix ::= "r" | "u" | "R" | "U" | "f" | "F" + | "fr" | "Fr" | "fR" | "FR" | "rf" | "rF" | "Rf" | "RF" + shortstring ::= "'" shortstringitem* "'" | '"' shortstringitem* '"' + longstring ::= "\'\'\'" longstringitem* "\'\'\'" | '"""' longstringitem* '"""' + shortstringitem ::= shortstringchar | stringescapeseq + longstringitem ::= longstringchar | stringescapeseq + shortstringchar ::= <any source character except "\\" or newline or the quote> + longstringchar ::= <any source character except "\\"> + stringescapeseq ::= "\\" <any source character> + + bytesliteral ::= bytesprefix(shortbytes | longbytes) + bytesprefix ::= "b" | "B" | "br" | "Br" | "bR" | "BR" | "rb" | "rB" | "Rb" | "RB" + shortbytes ::= "'" shortbytesitem* "'" | '"' shortbytesitem* '"' + longbytes ::= "\'\'\'" longbytesitem* "\'\'\'" | '"""' longbytesitem* '"""' + shortbytesitem ::= shortbyteschar | bytesescapeseq + longbytesitem ::= longbyteschar | bytesescapeseq + shortbyteschar ::= <any ASCII character except "\\" or newline or the quote> + longbyteschar ::= <any ASCII character except "\\"> + bytesescapeseq ::= "\\" <any ASCII character> + +One syntactic restriction not indicated by these productions is that +whitespace is not allowed between the "stringprefix" or "bytesprefix" +and the rest of the literal. The source character set is defined by +the encoding declaration; it is UTF-8 if no encoding declaration is +given in the source file; see section Encoding declarations. + +In plain English: Both types of literals can be enclosed in matching +single quotes ("'") or double quotes ("""). They can also be enclosed +in matching groups of three single or double quotes (these are +generally referred to as *triple-quoted strings*). The backslash ("\\") +character is used to give special meaning to otherwise ordinary +characters like "n", which means ‘newline’ when escaped ("\\n"). It can +also be used to escape characters that otherwise have a special +meaning, such as newline, backslash itself, or the quote character. +See escape sequences below for examples. + +Bytes literals are always prefixed with "'b'" or "'B'"; they produce +an instance of the "bytes" type instead of the "str" type. They may +only contain ASCII characters; bytes with a numeric value of 128 or +greater must be expressed with escapes. + +Both string and bytes literals may optionally be prefixed with a +letter "'r'" or "'R'"; such constructs are called *raw string +literals* and *raw bytes literals* respectively and treat backslashes +as literal characters. As a result, in raw string literals, "'\\U'" +and "'\\u'" escapes are not treated specially. + +Added in version 3.3: The "'rb'" prefix of raw bytes literals has been +added as a synonym of "'br'".Support for the unicode legacy literal +("u'value'") was reintroduced to simplify the maintenance of dual +Python 2.x and 3.x codebases. See **PEP 414** for more information. + +A string literal with "'f'" or "'F'" in its prefix is a *formatted +string literal*; see f-strings. The "'f'" may be combined with "'r'", +but not with "'b'" or "'u'", therefore raw formatted strings are +possible, but formatted bytes literals are not. + +In triple-quoted literals, unescaped newlines and quotes are allowed +(and are retained), except that three unescaped quotes in a row +terminate the literal. (A “quote” is the character used to open the +literal, i.e. either "'" or """.) + + +Escape sequences +================ + +Unless an "'r'" or "'R'" prefix is present, escape sequences in string +and bytes literals are interpreted according to rules similar to those +used by Standard C. The recognized escape sequences are: + ++---------------------------+-----------------------------------+---------+ +| Escape Sequence | Meaning | Notes | +|===========================|===================================|=========| +| "\\"<newline> | Backslash and newline ignored | (1) | ++---------------------------+-----------------------------------+---------+ +| "\\\\" | Backslash ("\\") | | ++---------------------------+-----------------------------------+---------+ +| "\\'" | Single quote ("'") | | ++---------------------------+-----------------------------------+---------+ +| "\\"" | Double quote (""") | | ++---------------------------+-----------------------------------+---------+ +| "\\a" | ASCII Bell (BEL) | | ++---------------------------+-----------------------------------+---------+ +| "\\b" | ASCII Backspace (BS) | | ++---------------------------+-----------------------------------+---------+ +| "\\f" | ASCII Formfeed (FF) | | ++---------------------------+-----------------------------------+---------+ +| "\\n" | ASCII Linefeed (LF) | | ++---------------------------+-----------------------------------+---------+ +| "\\r" | ASCII Carriage Return (CR) | | ++---------------------------+-----------------------------------+---------+ +| "\\t" | ASCII Horizontal Tab (TAB) | | ++---------------------------+-----------------------------------+---------+ +| "\\v" | ASCII Vertical Tab (VT) | | ++---------------------------+-----------------------------------+---------+ +| "\\*ooo*" | Character with octal value *ooo* | (2,4) | ++---------------------------+-----------------------------------+---------+ +| "\\x*hh*" | Character with hex value *hh* | (3,4) | ++---------------------------+-----------------------------------+---------+ + +Escape sequences only recognized in string literals are: + ++---------------------------+-----------------------------------+---------+ +| Escape Sequence | Meaning | Notes | +|===========================|===================================|=========| +| "\\N{*name*}" | Character named *name* in the | (5) | +| | Unicode database | | ++---------------------------+-----------------------------------+---------+ +| "\\u*xxxx*" | Character with 16-bit hex value | (6) | +| | *xxxx* | | ++---------------------------+-----------------------------------+---------+ +| "\\U*xxxxxxxx*" | Character with 32-bit hex value | (7) | +| | *xxxxxxxx* | | ++---------------------------+-----------------------------------+---------+ + +Notes: + +1. A backslash can be added at the end of a line to ignore the + newline: + + >>> 'This string will not include \\ + ... backslashes or newline characters.' + 'This string will not include backslashes or newline characters.' + + The same result can be achieved using triple-quoted strings, or + parentheses and string literal concatenation. + +2. As in Standard C, up to three octal digits are accepted. + + Changed in version 3.11: Octal escapes with value larger than + "0o377" produce a "DeprecationWarning". + + Changed in version 3.12: Octal escapes with value larger than + "0o377" produce a "SyntaxWarning". In a future Python version they + will be eventually a "SyntaxError". + +3. Unlike in Standard C, exactly two hex digits are required. + +4. In a bytes literal, hexadecimal and octal escapes denote the byte + with the given value. In a string literal, these escapes denote a + Unicode character with the given value. + +5. Changed in version 3.3: Support for name aliases [1] has been + added. + +6. Exactly four hex digits are required. + +7. Any Unicode character can be encoded this way. Exactly eight hex + digits are required. + +Unlike Standard C, all unrecognized escape sequences are left in the +string unchanged, i.e., *the backslash is left in the result*. (This +behavior is useful when debugging: if an escape sequence is mistyped, +the resulting output is more easily recognized as broken.) It is also +important to note that the escape sequences only recognized in string +literals fall into the category of unrecognized escapes for bytes +literals. + +Changed in version 3.6: Unrecognized escape sequences produce a +"DeprecationWarning". + +Changed in version 3.12: Unrecognized escape sequences produce a +"SyntaxWarning". In a future Python version they will be eventually a +"SyntaxError". + +Even in a raw literal, quotes can be escaped with a backslash, but the +backslash remains in the result; for example, "r"\\""" is a valid +string literal consisting of two characters: a backslash and a double +quote; "r"\\"" is not a valid string literal (even a raw string cannot +end in an odd number of backslashes). Specifically, *a raw literal +cannot end in a single backslash* (since the backslash would escape +the following quote character). Note also that a single backslash +followed by a newline is interpreted as those two characters as part +of the literal, *not* as a line continuation. +''', + 'subscriptions': r'''Subscriptions +************* + +The subscription of an instance of a container class will generally +select an element from the container. The subscription of a *generic +class* will generally return a GenericAlias object. + + subscription ::= primary "[" flexible_expression_list "]" + +When an object is subscripted, the interpreter will evaluate the +primary and the expression list. + +The primary must evaluate to an object that supports subscription. An +object may support subscription through defining one or both of +"__getitem__()" and "__class_getitem__()". When the primary is +subscripted, the evaluated result of the expression list will be +passed to one of these methods. For more details on when +"__class_getitem__" is called instead of "__getitem__", see +__class_getitem__ versus __getitem__. + +If the expression list contains at least one comma, or if any of the +expressions are starred, the expression list will evaluate to a +"tuple" containing the items of the expression list. Otherwise, the +expression list will evaluate to the value of the list’s sole member. + +Changed in version 3.11: Expressions in an expression list may be +starred. See **PEP 646**. + +For built-in objects, there are two types of objects that support +subscription via "__getitem__()": + +1. Mappings. If the primary is a *mapping*, the expression list must + evaluate to an object whose value is one of the keys of the + mapping, and the subscription selects the value in the mapping that + corresponds to that key. An example of a builtin mapping class is + the "dict" class. + +2. Sequences. If the primary is a *sequence*, the expression list must + evaluate to an "int" or a "slice" (as discussed in the following + section). Examples of builtin sequence classes include the "str", + "list" and "tuple" classes. + +The formal syntax makes no special provision for negative indices in +*sequences*. However, built-in sequences all provide a "__getitem__()" +method that interprets negative indices by adding the length of the +sequence to the index so that, for example, "x[-1]" selects the last +item of "x". The resulting value must be a nonnegative integer less +than the number of items in the sequence, and the subscription selects +the item whose index is that value (counting from zero). Since the +support for negative indices and slicing occurs in the object’s +"__getitem__()" method, subclasses overriding this method will need to +explicitly add that support. + +A "string" is a special kind of sequence whose items are *characters*. +A character is not a separate data type but a string of exactly one +character. +''', + 'truth': r'''Truth Value Testing +******************* + +Any object can be tested for truth value, for use in an "if" or +"while" condition or as operand of the Boolean operations below. + +By default, an object is considered true unless its class defines +either a "__bool__()" method that returns "False" or a "__len__()" +method that returns zero, when called with the object. [1] Here are +most of the built-in objects considered false: + +* constants defined to be false: "None" and "False" + +* zero of any numeric type: "0", "0.0", "0j", "Decimal(0)", + "Fraction(0, 1)" + +* empty sequences and collections: "''", "()", "[]", "{}", "set()", + "range(0)" + +Operations and built-in functions that have a Boolean result always +return "0" or "False" for false and "1" or "True" for true, unless +otherwise stated. (Important exception: the Boolean operations "or" +and "and" always return one of their operands.) +''', + 'try': r'''The "try" statement +******************* + +The "try" statement specifies exception handlers and/or cleanup code +for a group of statements: + + try_stmt ::= try1_stmt | try2_stmt | try3_stmt + try1_stmt ::= "try" ":" suite + ("except" [expression ["as" identifier]] ":" suite)+ + ["else" ":" suite] + ["finally" ":" suite] + try2_stmt ::= "try" ":" suite + ("except" "*" expression ["as" identifier] ":" suite)+ + ["else" ":" suite] + ["finally" ":" suite] + try3_stmt ::= "try" ":" suite + "finally" ":" suite + +Additional information on exceptions can be found in section +Exceptions, and information on using the "raise" statement to generate +exceptions may be found in section The raise statement. + + +"except" clause +=============== + +The "except" clause(s) specify one or more exception handlers. When no +exception occurs in the "try" clause, no exception handler is +executed. When an exception occurs in the "try" suite, a search for an +exception handler is started. This search inspects the "except" +clauses in turn until one is found that matches the exception. An +expression-less "except" clause, if present, must be last; it matches +any exception. + +For an "except" clause with an expression, the expression must +evaluate to an exception type or a tuple of exception types. The +raised exception matches an "except" clause whose expression evaluates +to the class or a *non-virtual base class* of the exception object, or +to a tuple that contains such a class. + +If no "except" clause matches the exception, the search for an +exception handler continues in the surrounding code and on the +invocation stack. [1] + +If the evaluation of an expression in the header of an "except" clause +raises an exception, the original search for a handler is canceled and +a search starts for the new exception in the surrounding code and on +the call stack (it is treated as if the entire "try" statement raised +the exception). + +When a matching "except" clause is found, the exception is assigned to +the target specified after the "as" keyword in that "except" clause, +if present, and the "except" clause’s suite is executed. All "except" +clauses must have an executable block. When the end of this block is +reached, execution continues normally after the entire "try" +statement. (This means that if two nested handlers exist for the same +exception, and the exception occurs in the "try" clause of the inner +handler, the outer handler will not handle the exception.) + +When an exception has been assigned using "as target", it is cleared +at the end of the "except" clause. This is as if + + except E as N: + foo + +was translated to + + except E as N: + try: + foo + finally: + del N + +This means the exception must be assigned to a different name to be +able to refer to it after the "except" clause. Exceptions are cleared +because with the traceback attached to them, they form a reference +cycle with the stack frame, keeping all locals in that frame alive +until the next garbage collection occurs. + +Before an "except" clause’s suite is executed, the exception is stored +in the "sys" module, where it can be accessed from within the body of +the "except" clause by calling "sys.exception()". When leaving an +exception handler, the exception stored in the "sys" module is reset +to its previous value: + + >>> print(sys.exception()) + None + >>> try: + ... raise TypeError + ... except: + ... print(repr(sys.exception())) + ... try: + ... raise ValueError + ... except: + ... print(repr(sys.exception())) + ... print(repr(sys.exception())) + ... + TypeError() + ValueError() + TypeError() + >>> print(sys.exception()) + None + + +"except*" clause +================ + +The "except*" clause(s) are used for handling "ExceptionGroup"s. The +exception type for matching is interpreted as in the case of "except", +but in the case of exception groups we can have partial matches when +the type matches some of the exceptions in the group. This means that +multiple "except*" clauses can execute, each handling part of the +exception group. Each clause executes at most once and handles an +exception group of all matching exceptions. Each exception in the +group is handled by at most one "except*" clause, the first that +matches it. + + >>> try: + ... raise ExceptionGroup("eg", + ... [ValueError(1), TypeError(2), OSError(3), OSError(4)]) + ... except* TypeError as e: + ... print(f'caught {type(e)} with nested {e.exceptions}') + ... except* OSError as e: + ... print(f'caught {type(e)} with nested {e.exceptions}') + ... + caught <class 'ExceptionGroup'> with nested (TypeError(2),) + caught <class 'ExceptionGroup'> with nested (OSError(3), OSError(4)) + + Exception Group Traceback (most recent call last): + | File "<stdin>", line 2, in <module> + | ExceptionGroup: eg + +-+---------------- 1 ---------------- + | ValueError: 1 + +------------------------------------ + +Any remaining exceptions that were not handled by any "except*" clause +are re-raised at the end, along with all exceptions that were raised +from within the "except*" clauses. If this list contains more than one +exception to reraise, they are combined into an exception group. + +If the raised exception is not an exception group and its type matches +one of the "except*" clauses, it is caught and wrapped by an exception +group with an empty message string. + + >>> try: + ... raise BlockingIOError + ... except* BlockingIOError as e: + ... print(repr(e)) + ... + ExceptionGroup('', (BlockingIOError())) + +An "except*" clause must have a matching expression; it cannot be +"except*:". Furthermore, this expression cannot contain exception +group types, because that would have ambiguous semantics. + +It is not possible to mix "except" and "except*" in the same "try". +"break", "continue" and "return" cannot appear in an "except*" clause. + + +"else" clause +============= + +The optional "else" clause is executed if the control flow leaves the +"try" suite, no exception was raised, and no "return", "continue", or +"break" statement was executed. Exceptions in the "else" clause are +not handled by the preceding "except" clauses. + + +"finally" clause +================ + +If "finally" is present, it specifies a ‘cleanup’ handler. The "try" +clause is executed, including any "except" and "else" clauses. If an +exception occurs in any of the clauses and is not handled, the +exception is temporarily saved. The "finally" clause is executed. If +there is a saved exception it is re-raised at the end of the "finally" +clause. If the "finally" clause raises another exception, the saved +exception is set as the context of the new exception. If the "finally" +clause executes a "return", "break" or "continue" statement, the saved +exception is discarded: + + >>> def f(): + ... try: + ... 1/0 + ... finally: + ... return 42 + ... + >>> f() + 42 + +The exception information is not available to the program during +execution of the "finally" clause. + +When a "return", "break" or "continue" statement is executed in the +"try" suite of a "try"…"finally" statement, the "finally" clause is +also executed ‘on the way out.’ + +The return value of a function is determined by the last "return" +statement executed. Since the "finally" clause always executes, a +"return" statement executed in the "finally" clause will always be the +last one executed: + + >>> def foo(): + ... try: + ... return 'try' + ... finally: + ... return 'finally' + ... + >>> foo() + 'finally' + +Changed in version 3.8: Prior to Python 3.8, a "continue" statement +was illegal in the "finally" clause due to a problem with the +implementation. +''', + 'types': r'''The standard type hierarchy +*************************** + +Below is a list of the types that are built into Python. Extension +modules (written in C, Java, or other languages, depending on the +implementation) can define additional types. Future versions of +Python may add types to the type hierarchy (e.g., rational numbers, +efficiently stored arrays of integers, etc.), although such additions +will often be provided via the standard library instead. + +Some of the type descriptions below contain a paragraph listing +‘special attributes.’ These are attributes that provide access to the +implementation and are not intended for general use. Their definition +may change in the future. + + +None +==== + +This type has a single value. There is a single object with this +value. This object is accessed through the built-in name "None". It is +used to signify the absence of a value in many situations, e.g., it is +returned from functions that don’t explicitly return anything. Its +truth value is false. + + +NotImplemented +============== + +This type has a single value. There is a single object with this +value. This object is accessed through the built-in name +"NotImplemented". Numeric methods and rich comparison methods should +return this value if they do not implement the operation for the +operands provided. (The interpreter will then try the reflected +operation, or some other fallback, depending on the operator.) It +should not be evaluated in a boolean context. + +See Implementing the arithmetic operations for more details. + +Changed in version 3.9: Evaluating "NotImplemented" in a boolean +context was deprecated. + +Changed in version 3.14: Evaluating "NotImplemented" in a boolean +context now raises a "TypeError". It previously evaluated to "True" +and emitted a "DeprecationWarning" since Python 3.9. + + +Ellipsis +======== + +This type has a single value. There is a single object with this +value. This object is accessed through the literal "..." or the built- +in name "Ellipsis". Its truth value is true. + + +"numbers.Number" +================ + +These are created by numeric literals and returned as results by +arithmetic operators and arithmetic built-in functions. Numeric +objects are immutable; once created their value never changes. Python +numbers are of course strongly related to mathematical numbers, but +subject to the limitations of numerical representation in computers. + +The string representations of the numeric classes, computed by +"__repr__()" and "__str__()", have the following properties: + +* They are valid numeric literals which, when passed to their class + constructor, produce an object having the value of the original + numeric. + +* The representation is in base 10, when possible. + +* Leading zeros, possibly excepting a single zero before a decimal + point, are not shown. + +* Trailing zeros, possibly excepting a single zero after a decimal + point, are not shown. + +* A sign is shown only when the number is negative. + +Python distinguishes between integers, floating-point numbers, and +complex numbers: + + +"numbers.Integral" +------------------ + +These represent elements from the mathematical set of integers +(positive and negative). + +Note: + + The rules for integer representation are intended to give the most + meaningful interpretation of shift and mask operations involving + negative integers. + +There are two types of integers: + +Integers ("int") + These represent numbers in an unlimited range, subject to available + (virtual) memory only. For the purpose of shift and mask + operations, a binary representation is assumed, and negative + numbers are represented in a variant of 2’s complement which gives + the illusion of an infinite string of sign bits extending to the + left. + +Booleans ("bool") + These represent the truth values False and True. The two objects + representing the values "False" and "True" are the only Boolean + objects. The Boolean type is a subtype of the integer type, and + Boolean values behave like the values 0 and 1, respectively, in + almost all contexts, the exception being that when converted to a + string, the strings ""False"" or ""True"" are returned, + respectively. + + +"numbers.Real" ("float") +------------------------ + +These represent machine-level double precision floating-point numbers. +You are at the mercy of the underlying machine architecture (and C or +Java implementation) for the accepted range and handling of overflow. +Python does not support single-precision floating-point numbers; the +savings in processor and memory usage that are usually the reason for +using these are dwarfed by the overhead of using objects in Python, so +there is no reason to complicate the language with two kinds of +floating-point numbers. + + +"numbers.Complex" ("complex") +----------------------------- + +These represent complex numbers as a pair of machine-level double +precision floating-point numbers. The same caveats apply as for +floating-point numbers. The real and imaginary parts of a complex +number "z" can be retrieved through the read-only attributes "z.real" +and "z.imag". + + +Sequences +========= + +These represent finite ordered sets indexed by non-negative numbers. +The built-in function "len()" returns the number of items of a +sequence. When the length of a sequence is *n*, the index set contains +the numbers 0, 1, …, *n*-1. Item *i* of sequence *a* is selected by +"a[i]". Some sequences, including built-in sequences, interpret +negative subscripts by adding the sequence length. For example, +"a[-2]" equals "a[n-2]", the second to last item of sequence a with +length "n". + +Sequences also support slicing: "a[i:j]" selects all items with index +*k* such that *i* "<=" *k* "<" *j*. When used as an expression, a +slice is a sequence of the same type. The comment above about negative +indexes also applies to negative slice positions. + +Some sequences also support “extended slicing” with a third “step” +parameter: "a[i:j:k]" selects all items of *a* with index *x* where "x += i + n*k", *n* ">=" "0" and *i* "<=" *x* "<" *j*. + +Sequences are distinguished according to their mutability: + + +Immutable sequences +------------------- + +An object of an immutable sequence type cannot change once it is +created. (If the object contains references to other objects, these +other objects may be mutable and may be changed; however, the +collection of objects directly referenced by an immutable object +cannot change.) + +The following types are immutable sequences: + +Strings + A string is a sequence of values that represent Unicode code + points. All the code points in the range "U+0000 - U+10FFFF" can be + represented in a string. Python doesn’t have a char type; instead, + every code point in the string is represented as a string object + with length "1". The built-in function "ord()" converts a code + point from its string form to an integer in the range "0 - 10FFFF"; + "chr()" converts an integer in the range "0 - 10FFFF" to the + corresponding length "1" string object. "str.encode()" can be used + to convert a "str" to "bytes" using the given text encoding, and + "bytes.decode()" can be used to achieve the opposite. + +Tuples + The items of a tuple are arbitrary Python objects. Tuples of two or + more items are formed by comma-separated lists of expressions. A + tuple of one item (a ‘singleton’) can be formed by affixing a comma + to an expression (an expression by itself does not create a tuple, + since parentheses must be usable for grouping of expressions). An + empty tuple can be formed by an empty pair of parentheses. + +Bytes + A bytes object is an immutable array. The items are 8-bit bytes, + represented by integers in the range 0 <= x < 256. Bytes literals + (like "b'abc'") and the built-in "bytes()" constructor can be used + to create bytes objects. Also, bytes objects can be decoded to + strings via the "decode()" method. + + +Mutable sequences +----------------- + +Mutable sequences can be changed after they are created. The +subscription and slicing notations can be used as the target of +assignment and "del" (delete) statements. + +Note: + + The "collections" and "array" module provide additional examples of + mutable sequence types. + +There are currently two intrinsic mutable sequence types: + +Lists + The items of a list are arbitrary Python objects. Lists are formed + by placing a comma-separated list of expressions in square + brackets. (Note that there are no special cases needed to form + lists of length 0 or 1.) + +Byte Arrays + A bytearray object is a mutable array. They are created by the + built-in "bytearray()" constructor. Aside from being mutable (and + hence unhashable), byte arrays otherwise provide the same interface + and functionality as immutable "bytes" objects. + + +Set types +========= + +These represent unordered, finite sets of unique, immutable objects. +As such, they cannot be indexed by any subscript. However, they can be +iterated over, and the built-in function "len()" returns the number of +items in a set. Common uses for sets are fast membership testing, +removing duplicates from a sequence, and computing mathematical +operations such as intersection, union, difference, and symmetric +difference. + +For set elements, the same immutability rules apply as for dictionary +keys. Note that numeric types obey the normal rules for numeric +comparison: if two numbers compare equal (e.g., "1" and "1.0"), only +one of them can be contained in a set. + +There are currently two intrinsic set types: + +Sets + These represent a mutable set. They are created by the built-in + "set()" constructor and can be modified afterwards by several + methods, such as "add()". + +Frozen sets + These represent an immutable set. They are created by the built-in + "frozenset()" constructor. As a frozenset is immutable and + *hashable*, it can be used again as an element of another set, or + as a dictionary key. + + +Mappings +======== + +These represent finite sets of objects indexed by arbitrary index +sets. The subscript notation "a[k]" selects the item indexed by "k" +from the mapping "a"; this can be used in expressions and as the +target of assignments or "del" statements. The built-in function +"len()" returns the number of items in a mapping. + +There is currently a single intrinsic mapping type: + + +Dictionaries +------------ + +These represent finite sets of objects indexed by nearly arbitrary +values. The only types of values not acceptable as keys are values +containing lists or dictionaries or other mutable types that are +compared by value rather than by object identity, the reason being +that the efficient implementation of dictionaries requires a key’s +hash value to remain constant. Numeric types used for keys obey the +normal rules for numeric comparison: if two numbers compare equal +(e.g., "1" and "1.0") then they can be used interchangeably to index +the same dictionary entry. + +Dictionaries preserve insertion order, meaning that keys will be +produced in the same order they were added sequentially over the +dictionary. Replacing an existing key does not change the order, +however removing a key and re-inserting it will add it to the end +instead of keeping its old place. + +Dictionaries are mutable; they can be created by the "{}" notation +(see section Dictionary displays). + +The extension modules "dbm.ndbm" and "dbm.gnu" provide additional +examples of mapping types, as does the "collections" module. + +Changed in version 3.7: Dictionaries did not preserve insertion order +in versions of Python before 3.6. In CPython 3.6, insertion order was +preserved, but it was considered an implementation detail at that time +rather than a language guarantee. + + +Callable types +============== + +These are the types to which the function call operation (see section +Calls) can be applied: + + +User-defined functions +---------------------- + +A user-defined function object is created by a function definition +(see section Function definitions). It should be called with an +argument list containing the same number of items as the function’s +formal parameter list. + + +Special read-only attributes +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + ++----------------------------------------------------+----------------------------------------------------+ +| Attribute | Meaning | +|====================================================|====================================================| +| function.__globals__ | A reference to the "dictionary" that holds the | +| | function’s global variables – the global namespace | +| | of the module in which the function was defined. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__closure__ | "None" or a "tuple" of cells that contain bindings | +| | for the names specified in the "co_freevars" | +| | attribute of the function’s "code object". A cell | +| | object has the attribute "cell_contents". This can | +| | be used to get the value of the cell, as well as | +| | set the value. | ++----------------------------------------------------+----------------------------------------------------+ + + +Special writable attributes +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Most of these attributes check the type of the assigned value: + ++----------------------------------------------------+----------------------------------------------------+ +| Attribute | Meaning | +|====================================================|====================================================| +| function.__doc__ | The function’s documentation string, or "None" if | +| | unavailable. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__name__ | The function’s name. See also: "__name__ | +| | attributes". | ++----------------------------------------------------+----------------------------------------------------+ +| function.__qualname__ | The function’s *qualified name*. See also: | +| | "__qualname__ attributes". Added in version 3.3. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__module__ | The name of the module the function was defined | +| | in, or "None" if unavailable. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__defaults__ | A "tuple" containing default *parameter* values | +| | for those parameters that have defaults, or "None" | +| | if no parameters have a default value. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__code__ | The code object representing the compiled function | +| | body. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__dict__ | The namespace supporting arbitrary function | +| | attributes. See also: "__dict__ attributes". | ++----------------------------------------------------+----------------------------------------------------+ +| function.__annotations__ | A "dictionary" containing annotations of | +| | *parameters*. The keys of the dictionary are the | +| | parameter names, and "'return'" for the return | +| | annotation, if provided. See also: | +| | "object.__annotations__". Changed in version | +| | 3.14: Annotations are now lazily evaluated. See | +| | **PEP 649**. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__annotate__ | The *annotate function* for this function, or | +| | "None" if the function has no annotations. See | +| | "object.__annotate__". Added in version 3.14. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__kwdefaults__ | A "dictionary" containing defaults for keyword- | +| | only *parameters*. | ++----------------------------------------------------+----------------------------------------------------+ +| function.__type_params__ | A "tuple" containing the type parameters of a | +| | generic function. Added in version 3.12. | ++----------------------------------------------------+----------------------------------------------------+ + +Function objects also support getting and setting arbitrary +attributes, which can be used, for example, to attach metadata to +functions. Regular attribute dot-notation is used to get and set such +attributes. + +**CPython implementation detail:** CPython’s current implementation +only supports function attributes on user-defined functions. Function +attributes on built-in functions may be supported in the future. + +Additional information about a function’s definition can be retrieved +from its code object (accessible via the "__code__" attribute). + + +Instance methods +---------------- + +An instance method object combines a class, a class instance and any +callable object (normally a user-defined function). + +Special read-only attributes: + ++----------------------------------------------------+----------------------------------------------------+ +| method.__self__ | Refers to the class instance object to which the | +| | method is bound | ++----------------------------------------------------+----------------------------------------------------+ +| method.__func__ | Refers to the original function object | ++----------------------------------------------------+----------------------------------------------------+ +| method.__doc__ | The method’s documentation (same as | +| | "method.__func__.__doc__"). A "string" if the | +| | original function had a docstring, else "None". | ++----------------------------------------------------+----------------------------------------------------+ +| method.__name__ | The name of the method (same as | +| | "method.__func__.__name__") | ++----------------------------------------------------+----------------------------------------------------+ +| method.__module__ | The name of the module the method was defined in, | +| | or "None" if unavailable. | ++----------------------------------------------------+----------------------------------------------------+ + +Methods also support accessing (but not setting) the arbitrary +function attributes on the underlying function object. + +User-defined method objects may be created when getting an attribute +of a class (perhaps via an instance of that class), if that attribute +is a user-defined function object or a "classmethod" object. + +When an instance method object is created by retrieving a user-defined +function object from a class via one of its instances, its "__self__" +attribute is the instance, and the method object is said to be +*bound*. The new method’s "__func__" attribute is the original +function object. + +When an instance method object is created by retrieving a +"classmethod" object from a class or instance, its "__self__" +attribute is the class itself, and its "__func__" attribute is the +function object underlying the class method. + +When an instance method object is called, the underlying function +("__func__") is called, inserting the class instance ("__self__") in +front of the argument list. For instance, when "C" is a class which +contains a definition for a function "f()", and "x" is an instance of +"C", calling "x.f(1)" is equivalent to calling "C.f(x, 1)". + +When an instance method object is derived from a "classmethod" object, +the “class instance” stored in "__self__" will actually be the class +itself, so that calling either "x.f(1)" or "C.f(1)" is equivalent to +calling "f(C,1)" where "f" is the underlying function. + +It is important to note that user-defined functions which are +attributes of a class instance are not converted to bound methods; +this *only* happens when the function is an attribute of the class. + + +Generator functions +------------------- + +A function or method which uses the "yield" statement (see section The +yield statement) is called a *generator function*. Such a function, +when called, always returns an *iterator* object which can be used to +execute the body of the function: calling the iterator’s +"iterator.__next__()" method will cause the function to execute until +it provides a value using the "yield" statement. When the function +executes a "return" statement or falls off the end, a "StopIteration" +exception is raised and the iterator will have reached the end of the +set of values to be returned. + + +Coroutine functions +------------------- + +A function or method which is defined using "async def" is called a +*coroutine function*. Such a function, when called, returns a +*coroutine* object. It may contain "await" expressions, as well as +"async with" and "async for" statements. See also the Coroutine +Objects section. + + +Asynchronous generator functions +-------------------------------- + +A function or method which is defined using "async def" and which uses +the "yield" statement is called a *asynchronous generator function*. +Such a function, when called, returns an *asynchronous iterator* +object which can be used in an "async for" statement to execute the +body of the function. + +Calling the asynchronous iterator’s "aiterator.__anext__" method will +return an *awaitable* which when awaited will execute until it +provides a value using the "yield" expression. When the function +executes an empty "return" statement or falls off the end, a +"StopAsyncIteration" exception is raised and the asynchronous iterator +will have reached the end of the set of values to be yielded. + + +Built-in functions +------------------ + +A built-in function object is a wrapper around a C function. Examples +of built-in functions are "len()" and "math.sin()" ("math" is a +standard built-in module). The number and type of the arguments are +determined by the C function. Special read-only attributes: + +* "__doc__" is the function’s documentation string, or "None" if + unavailable. See "function.__doc__". + +* "__name__" is the function’s name. See "function.__name__". + +* "__self__" is set to "None" (but see the next item). + +* "__module__" is the name of the module the function was defined in + or "None" if unavailable. See "function.__module__". + + +Built-in methods +---------------- + +This is really a different disguise of a built-in function, this time +containing an object passed to the C function as an implicit extra +argument. An example of a built-in method is "alist.append()", +assuming *alist* is a list object. In this case, the special read-only +attribute "__self__" is set to the object denoted by *alist*. (The +attribute has the same semantics as it does with "other instance +methods".) + + +Classes +------- + +Classes are callable. These objects normally act as factories for new +instances of themselves, but variations are possible for class types +that override "__new__()". The arguments of the call are passed to +"__new__()" and, in the typical case, to "__init__()" to initialize +the new instance. + + +Class Instances +--------------- + +Instances of arbitrary classes can be made callable by defining a +"__call__()" method in their class. + + +Modules +======= + +Modules are a basic organizational unit of Python code, and are +created by the import system as invoked either by the "import" +statement, or by calling functions such as "importlib.import_module()" +and built-in "__import__()". A module object has a namespace +implemented by a "dictionary" object (this is the dictionary +referenced by the "__globals__" attribute of functions defined in the +module). Attribute references are translated to lookups in this +dictionary, e.g., "m.x" is equivalent to "m.__dict__["x"]". A module +object does not contain the code object used to initialize the module +(since it isn’t needed once the initialization is done). + +Attribute assignment updates the module’s namespace dictionary, e.g., +"m.x = 1" is equivalent to "m.__dict__["x"] = 1". + + +Import-related attributes on module objects +------------------------------------------- + +Module objects have the following attributes that relate to the import +system. When a module is created using the machinery associated with +the import system, these attributes are filled in based on the +module’s *spec*, before the *loader* executes and loads the module. + +To create a module dynamically rather than using the import system, +it’s recommended to use "importlib.util.module_from_spec()", which +will set the various import-controlled attributes to appropriate +values. It’s also possible to use the "types.ModuleType" constructor +to create modules directly, but this technique is more error-prone, as +most attributes must be manually set on the module object after it has +been created when using this approach. + +Caution: + + With the exception of "__name__", it is **strongly** recommended + that you rely on "__spec__" and its attributes instead of any of the + other individual attributes listed in this subsection. Note that + updating an attribute on "__spec__" will not update the + corresponding attribute on the module itself: + + >>> import typing + >>> typing.__name__, typing.__spec__.name + ('typing', 'typing') + >>> typing.__spec__.name = 'spelling' + >>> typing.__name__, typing.__spec__.name + ('typing', 'spelling') + >>> typing.__name__ = 'keyboard_smashing' + >>> typing.__name__, typing.__spec__.name + ('keyboard_smashing', 'spelling') + +module.__name__ + + The name used to uniquely identify the module in the import system. + For a directly executed module, this will be set to ""__main__"". + + This attribute must be set to the fully qualified name of the + module. It is expected to match the value of + "module.__spec__.name". + +module.__spec__ + + A record of the module’s import-system-related state. + + Set to the "module spec" that was used when importing the module. + See Module specs for more details. + + Added in version 3.4. + +module.__package__ + + The *package* a module belongs to. + + If the module is top-level (that is, not a part of any specific + package) then the attribute should be set to "''" (the empty + string). Otherwise, it should be set to the name of the module’s + package (which can be equal to "module.__name__" if the module + itself is a package). See **PEP 366** for further details. + + This attribute is used instead of "__name__" to calculate explicit + relative imports for main modules. It defaults to "None" for + modules created dynamically using the "types.ModuleType" + constructor; use "importlib.util.module_from_spec()" instead to + ensure the attribute is set to a "str". + + It is **strongly** recommended that you use + "module.__spec__.parent" instead of "module.__package__". + "__package__" is now only used as a fallback if "__spec__.parent" + is not set, and this fallback path is deprecated. + + Changed in version 3.4: This attribute now defaults to "None" for + modules created dynamically using the "types.ModuleType" + constructor. Previously the attribute was optional. + + Changed in version 3.6: The value of "__package__" is expected to + be the same as "__spec__.parent". "__package__" is now only used as + a fallback during import resolution if "__spec__.parent" is not + defined. + + Changed in version 3.10: "ImportWarning" is raised if an import + resolution falls back to "__package__" instead of + "__spec__.parent". + + Changed in version 3.12: Raise "DeprecationWarning" instead of + "ImportWarning" when falling back to "__package__" during import + resolution. + + Deprecated since version 3.13, will be removed in version 3.15: + "__package__" will cease to be set or taken into consideration by + the import system or standard library. + +module.__loader__ + + The *loader* object that the import machinery used to load the + module. + + This attribute is mostly useful for introspection, but can be used + for additional loader-specific functionality, for example getting + data associated with a loader. + + "__loader__" defaults to "None" for modules created dynamically + using the "types.ModuleType" constructor; use + "importlib.util.module_from_spec()" instead to ensure the attribute + is set to a *loader* object. + + It is **strongly** recommended that you use + "module.__spec__.loader" instead of "module.__loader__". + + Changed in version 3.4: This attribute now defaults to "None" for + modules created dynamically using the "types.ModuleType" + constructor. Previously the attribute was optional. + + Deprecated since version 3.12, will be removed in version 3.16: + Setting "__loader__" on a module while failing to set + "__spec__.loader" is deprecated. In Python 3.16, "__loader__" will + cease to be set or taken into consideration by the import system or + the standard library. + +module.__path__ + + A (possibly empty) *sequence* of strings enumerating the locations + where the package’s submodules will be found. Non-package modules + should not have a "__path__" attribute. See __path__ attributes on + modules for more details. + + It is **strongly** recommended that you use + "module.__spec__.submodule_search_locations" instead of + "module.__path__". + +module.__file__ + +module.__cached__ + + "__file__" and "__cached__" are both optional attributes that may + or may not be set. Both attributes should be a "str" when they are + available. + + "__file__" indicates the pathname of the file from which the module + was loaded (if loaded from a file), or the pathname of the shared + library file for extension modules loaded dynamically from a shared + library. It might be missing for certain types of modules, such as + C modules that are statically linked into the interpreter, and the + import system may opt to leave it unset if it has no semantic + meaning (for example, a module loaded from a database). + + If "__file__" is set then the "__cached__" attribute might also be + set, which is the path to any compiled version of the code (for + example, a byte-compiled file). The file does not need to exist to + set this attribute; the path can simply point to where the compiled + file *would* exist (see **PEP 3147**). + + Note that "__cached__" may be set even if "__file__" is not set. + However, that scenario is quite atypical. Ultimately, the *loader* + is what makes use of the module spec provided by the *finder* (from + which "__file__" and "__cached__" are derived). So if a loader can + load from a cached module but otherwise does not load from a file, + that atypical scenario may be appropriate. + + It is **strongly** recommended that you use + "module.__spec__.cached" instead of "module.__cached__". + + Deprecated since version 3.13, will be removed in version 3.15: + Setting "__cached__" on a module while failing to set + "__spec__.cached" is deprecated. In Python 3.15, "__cached__" will + cease to be set or taken into consideration by the import system or + standard library. + + +Other writable attributes on module objects +------------------------------------------- + +As well as the import-related attributes listed above, module objects +also have the following writable attributes: + +module.__doc__ + + The module’s documentation string, or "None" if unavailable. See + also: "__doc__ attributes". + +module.__annotations__ + + A dictionary containing *variable annotations* collected during + module body execution. For best practices on working with + "__annotations__", see "annotationlib". + + Changed in version 3.14: Annotations are now lazily evaluated. See + **PEP 649**. + +module.__annotate__ + + The *annotate function* for this module, or "None" if the module + has no annotations. See also: "__annotate__" attributes. + + Added in version 3.14. + + +Module dictionaries +------------------- + +Module objects also have the following special read-only attribute: + +module.__dict__ + + The module’s namespace as a dictionary object. Uniquely among the + attributes listed here, "__dict__" cannot be accessed as a global + variable from within a module; it can only be accessed as an + attribute on module objects. + + **CPython implementation detail:** Because of the way CPython + clears module dictionaries, the module dictionary will be cleared + when the module falls out of scope even if the dictionary still has + live references. To avoid this, copy the dictionary or keep the + module around while using its dictionary directly. + + +Custom classes +============== + +Custom class types are typically created by class definitions (see +section Class definitions). A class has a namespace implemented by a +dictionary object. Class attribute references are translated to +lookups in this dictionary, e.g., "C.x" is translated to +"C.__dict__["x"]" (although there are a number of hooks which allow +for other means of locating attributes). When the attribute name is +not found there, the attribute search continues in the base classes. +This search of the base classes uses the C3 method resolution order +which behaves correctly even in the presence of ‘diamond’ inheritance +structures where there are multiple inheritance paths leading back to +a common ancestor. Additional details on the C3 MRO used by Python can +be found at The Python 2.3 Method Resolution Order. + +When a class attribute reference (for class "C", say) would yield a +class method object, it is transformed into an instance method object +whose "__self__" attribute is "C". When it would yield a +"staticmethod" object, it is transformed into the object wrapped by +the static method object. See section Implementing Descriptors for +another way in which attributes retrieved from a class may differ from +those actually contained in its "__dict__". + +Class attribute assignments update the class’s dictionary, never the +dictionary of a base class. + +A class object can be called (see above) to yield a class instance +(see below). + + +Special attributes +------------------ + ++----------------------------------------------------+----------------------------------------------------+ +| Attribute | Meaning | +|====================================================|====================================================| +| type.__name__ | The class’s name. See also: "__name__ attributes". | ++----------------------------------------------------+----------------------------------------------------+ +| type.__qualname__ | The class’s *qualified name*. See also: | +| | "__qualname__ attributes". | ++----------------------------------------------------+----------------------------------------------------+ +| type.__module__ | The name of the module in which the class was | +| | defined. | ++----------------------------------------------------+----------------------------------------------------+ +| type.__dict__ | A "mapping proxy" providing a read-only view of | +| | the class’s namespace. See also: "__dict__ | +| | attributes". | ++----------------------------------------------------+----------------------------------------------------+ +| type.__bases__ | A "tuple" containing the class’s bases. In most | +| | cases, for a class defined as "class X(A, B, C)", | +| | "X.__bases__" will be exactly equal to "(A, B, | +| | C)". | ++----------------------------------------------------+----------------------------------------------------+ +| type.__doc__ | The class’s documentation string, or "None" if | +| | undefined. Not inherited by subclasses. | ++----------------------------------------------------+----------------------------------------------------+ +| type.__annotations__ | A dictionary containing *variable annotations* | +| | collected during class body execution. See also: | +| | "__annotations__ attributes". For best practices | +| | on working with "__annotations__", please see | +| | "annotationlib". Caution: Accessing the | +| | "__annotations__" attribute of a class object | +| | directly may yield incorrect results in the | +| | presence of metaclasses. In addition, the | +| | attribute may not exist for some classes. Use | +| | "annotationlib.get_annotations()" to retrieve | +| | class annotations safely. Changed in version | +| | 3.14: Annotations are now lazily evaluated. See | +| | **PEP 649**. | ++----------------------------------------------------+----------------------------------------------------+ +| type.__annotate__() | The *annotate function* for this class, or "None" | +| | if the class has no annotations. See also: | +| | "__annotate__ attributes". Caution: Accessing | +| | the "__annotate__" attribute of a class object | +| | directly may yield incorrect results in the | +| | presence of metaclasses. Use | +| | "annotationlib.get_annotate_function()" to | +| | retrieve the annotate function safely. Added in | +| | version 3.14. | ++----------------------------------------------------+----------------------------------------------------+ +| type.__type_params__ | A "tuple" containing the type parameters of a | +| | generic class. Added in version 3.12. | ++----------------------------------------------------+----------------------------------------------------+ +| type.__static_attributes__ | A "tuple" containing names of attributes of this | +| | class which are assigned through "self.X" from any | +| | function in its body. Added in version 3.13. | ++----------------------------------------------------+----------------------------------------------------+ +| type.__firstlineno__ | The line number of the first line of the class | +| | definition, including decorators. Setting the | +| | "__module__" attribute removes the | +| | "__firstlineno__" item from the type’s dictionary. | +| | Added in version 3.13. | ++----------------------------------------------------+----------------------------------------------------+ +| type.__mro__ | The "tuple" of classes that are considered when | +| | looking for base classes during method resolution. | ++----------------------------------------------------+----------------------------------------------------+ + + +Special methods +--------------- + +In addition to the special attributes described above, all Python +classes also have the following two methods available: + +type.mro() + + This method can be overridden by a metaclass to customize the + method resolution order for its instances. It is called at class + instantiation, and its result is stored in "__mro__". + +type.__subclasses__() + + Each class keeps a list of weak references to its immediate + subclasses. This method returns a list of all those references + still alive. The list is in definition order. Example: + + >>> class A: pass + >>> class B(A): pass + >>> A.__subclasses__() + [<class 'B'>] + + +Class instances +=============== + +A class instance is created by calling a class object (see above). A +class instance has a namespace implemented as a dictionary which is +the first place in which attribute references are searched. When an +attribute is not found there, and the instance’s class has an +attribute by that name, the search continues with the class +attributes. If a class attribute is found that is a user-defined +function object, it is transformed into an instance method object +whose "__self__" attribute is the instance. Static method and class +method objects are also transformed; see above under “Classes”. See +section Implementing Descriptors for another way in which attributes +of a class retrieved via its instances may differ from the objects +actually stored in the class’s "__dict__". If no class attribute is +found, and the object’s class has a "__getattr__()" method, that is +called to satisfy the lookup. + +Attribute assignments and deletions update the instance’s dictionary, +never a class’s dictionary. If the class has a "__setattr__()" or +"__delattr__()" method, this is called instead of updating the +instance dictionary directly. + +Class instances can pretend to be numbers, sequences, or mappings if +they have methods with certain special names. See section Special +method names. + + +Special attributes +------------------ + +object.__class__ + + The class to which a class instance belongs. + +object.__dict__ + + A dictionary or other mapping object used to store an object’s + (writable) attributes. Not all instances have a "__dict__" + attribute; see the section on __slots__ for more details. + + +I/O objects (also known as file objects) +======================================== + +A *file object* represents an open file. Various shortcuts are +available to create file objects: the "open()" built-in function, and +also "os.popen()", "os.fdopen()", and the "makefile()" method of +socket objects (and perhaps by other functions or methods provided by +extension modules). + +The objects "sys.stdin", "sys.stdout" and "sys.stderr" are initialized +to file objects corresponding to the interpreter’s standard input, +output and error streams; they are all open in text mode and therefore +follow the interface defined by the "io.TextIOBase" abstract class. + + +Internal types +============== + +A few types used internally by the interpreter are exposed to the +user. Their definitions may change with future versions of the +interpreter, but they are mentioned here for completeness. + + +Code objects +------------ + +Code objects represent *byte-compiled* executable Python code, or +*bytecode*. The difference between a code object and a function object +is that the function object contains an explicit reference to the +function’s globals (the module in which it was defined), while a code +object contains no context; also the default argument values are +stored in the function object, not in the code object (because they +represent values calculated at run-time). Unlike function objects, +code objects are immutable and contain no references (directly or +indirectly) to mutable objects. + + +Special read-only attributes +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_name | The function name | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_qualname | The fully qualified function name Added in | +| | version 3.11. | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_argcount | The total number of positional *parameters* | +| | (including positional-only parameters and | +| | parameters with default values) that the function | +| | has | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_posonlyargcount | The number of positional-only *parameters* | +| | (including arguments with default values) that the | +| | function has | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_kwonlyargcount | The number of keyword-only *parameters* (including | +| | arguments with default values) that the function | +| | has | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_nlocals | The number of local variables used by the function | +| | (including parameters) | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_varnames | A "tuple" containing the names of the local | +| | variables in the function (starting with the | +| | parameter names) | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_cellvars | A "tuple" containing the names of local variables | +| | that are referenced from at least one *nested | +| | scope* inside the function | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_freevars | A "tuple" containing the names of *free (closure) | +| | variables* that a *nested scope* references in an | +| | outer scope. See also "function.__closure__". | +| | Note: references to global and builtin names are | +| | *not* included. | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_code | A string representing the sequence of *bytecode* | +| | instructions in the function | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_consts | A "tuple" containing the literals used by the | +| | *bytecode* in the function | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_names | A "tuple" containing the names used by the | +| | *bytecode* in the function | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_filename | The name of the file from which the code was | +| | compiled | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_firstlineno | The line number of the first line of the function | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_lnotab | A string encoding the mapping from *bytecode* | +| | offsets to line numbers. For details, see the | +| | source code of the interpreter. Deprecated since | +| | version 3.12: This attribute of code objects is | +| | deprecated, and may be removed in Python 3.15. | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_stacksize | The required stack size of the code object | ++----------------------------------------------------+----------------------------------------------------+ +| codeobject.co_flags | An "integer" encoding a number of flags for the | +| | interpreter. | ++----------------------------------------------------+----------------------------------------------------+ + +The following flag bits are defined for "co_flags": bit "0x04" is set +if the function uses the "*arguments" syntax to accept an arbitrary +number of positional arguments; bit "0x08" is set if the function uses +the "**keywords" syntax to accept arbitrary keyword arguments; bit +"0x20" is set if the function is a generator. See Code Objects Bit +Flags for details on the semantics of each flags that might be +present. + +Future feature declarations ("from __future__ import division") also +use bits in "co_flags" to indicate whether a code object was compiled +with a particular feature enabled: bit "0x2000" is set if the function +was compiled with future division enabled; bits "0x10" and "0x1000" +were used in earlier versions of Python. + +Other bits in "co_flags" are reserved for internal use. + +If a code object represents a function and has a docstring, the first +item in "co_consts" is the docstring of the function. + + +Methods on code objects +~~~~~~~~~~~~~~~~~~~~~~~ + +codeobject.co_positions() + + Returns an iterable over the source code positions of each + *bytecode* instruction in the code object. + + The iterator returns "tuple"s containing the "(start_line, + end_line, start_column, end_column)". The *i-th* tuple corresponds + to the position of the source code that compiled to the *i-th* code + unit. Column information is 0-indexed utf-8 byte offsets on the + given source line. + + This positional information can be missing. A non-exhaustive lists + of cases where this may happen: + + * Running the interpreter with "-X" "no_debug_ranges". + + * Loading a pyc file compiled while using "-X" "no_debug_ranges". + + * Position tuples corresponding to artificial instructions. + + * Line and column numbers that can’t be represented due to + implementation specific limitations. + + When this occurs, some or all of the tuple elements can be "None". + + Added in version 3.11. + + Note: + + This feature requires storing column positions in code objects + which may result in a small increase of disk usage of compiled + Python files or interpreter memory usage. To avoid storing the + extra information and/or deactivate printing the extra traceback + information, the "-X" "no_debug_ranges" command line flag or the + "PYTHONNODEBUGRANGES" environment variable can be used. + +codeobject.co_lines() + + Returns an iterator that yields information about successive ranges + of *bytecode*s. Each item yielded is a "(start, end, lineno)" + "tuple": + + * "start" (an "int") represents the offset (inclusive) of the start + of the *bytecode* range + + * "end" (an "int") represents the offset (exclusive) of the end of + the *bytecode* range + + * "lineno" is an "int" representing the line number of the + *bytecode* range, or "None" if the bytecodes in the given range + have no line number + + The items yielded will have the following properties: + + * The first range yielded will have a "start" of 0. + + * The "(start, end)" ranges will be non-decreasing and consecutive. + That is, for any pair of "tuple"s, the "start" of the second will + be equal to the "end" of the first. + + * No range will be backwards: "end >= start" for all triples. + + * The last "tuple" yielded will have "end" equal to the size of the + *bytecode*. + + Zero-width ranges, where "start == end", are allowed. Zero-width + ranges are used for lines that are present in the source code, but + have been eliminated by the *bytecode* compiler. + + Added in version 3.10. + + See also: + + **PEP 626** - Precise line numbers for debugging and other tools. + The PEP that introduced the "co_lines()" method. + +codeobject.replace(**kwargs) + + Return a copy of the code object with new values for the specified + fields. + + Code objects are also supported by the generic function + "copy.replace()". + + Added in version 3.8. + + +Frame objects +------------- + +Frame objects represent execution frames. They may occur in traceback +objects, and are also passed to registered trace functions. + + +Special read-only attributes +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_back | Points to the previous stack frame (towards the | +| | caller), or "None" if this is the bottom stack | +| | frame | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_code | The code object being executed in this frame. | +| | Accessing this attribute raises an auditing event | +| | "object.__getattr__" with arguments "obj" and | +| | ""f_code"". | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_locals | The mapping used by the frame to look up local | +| | variables. If the frame refers to an *optimized | +| | scope*, this may return a write-through proxy | +| | object. Changed in version 3.13: Return a proxy | +| | for optimized scopes. | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_globals | The dictionary used by the frame to look up global | +| | variables | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_builtins | The dictionary used by the frame to look up built- | +| | in (intrinsic) names | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_lasti | The “precise instruction” of the frame object | +| | (this is an index into the *bytecode* string of | +| | the code object) | ++----------------------------------------------------+----------------------------------------------------+ + + +Special writable attributes +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_trace | If not "None", this is a function called for | +| | various events during code execution (this is used | +| | by debuggers). Normally an event is triggered for | +| | each new source line (see "f_trace_lines"). | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_trace_lines | Set this attribute to "False" to disable | +| | triggering a tracing event for each source line. | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_trace_opcodes | Set this attribute to "True" to allow per-opcode | +| | events to be requested. Note that this may lead to | +| | undefined interpreter behaviour if exceptions | +| | raised by the trace function escape to the | +| | function being traced. | ++----------------------------------------------------+----------------------------------------------------+ +| frame.f_lineno | The current line number of the frame – writing to | +| | this from within a trace function jumps to the | +| | given line (only for the bottom-most frame). A | +| | debugger can implement a Jump command (aka Set | +| | Next Statement) by writing to this attribute. | ++----------------------------------------------------+----------------------------------------------------+ + + +Frame object methods +~~~~~~~~~~~~~~~~~~~~ + +Frame objects support one method: + +frame.clear() + + This method clears all references to local variables held by the + frame. Also, if the frame belonged to a *generator*, the generator + is finalized. This helps break reference cycles involving frame + objects (for example when catching an exception and storing its + traceback for later use). + + "RuntimeError" is raised if the frame is currently executing or + suspended. + + Added in version 3.4. + + Changed in version 3.13: Attempting to clear a suspended frame + raises "RuntimeError" (as has always been the case for executing + frames). + + +Traceback objects +----------------- + +Traceback objects represent the stack trace of an exception. A +traceback object is implicitly created when an exception occurs, and +may also be explicitly created by calling "types.TracebackType". + +Changed in version 3.7: Traceback objects can now be explicitly +instantiated from Python code. + +For implicitly created tracebacks, when the search for an exception +handler unwinds the execution stack, at each unwound level a traceback +object is inserted in front of the current traceback. When an +exception handler is entered, the stack trace is made available to the +program. (See section The try statement.) It is accessible as the +third item of the tuple returned by "sys.exc_info()", and as the +"__traceback__" attribute of the caught exception. + +When the program contains no suitable handler, the stack trace is +written (nicely formatted) to the standard error stream; if the +interpreter is interactive, it is also made available to the user as +"sys.last_traceback". + +For explicitly created tracebacks, it is up to the creator of the +traceback to determine how the "tb_next" attributes should be linked +to form a full stack trace. + +Special read-only attributes: + ++----------------------------------------------------+----------------------------------------------------+ +| traceback.tb_frame | Points to the execution frame of the current | +| | level. Accessing this attribute raises an | +| | auditing event "object.__getattr__" with arguments | +| | "obj" and ""tb_frame"". | ++----------------------------------------------------+----------------------------------------------------+ +| traceback.tb_lineno | Gives the line number where the exception occurred | ++----------------------------------------------------+----------------------------------------------------+ +| traceback.tb_lasti | Indicates the “precise instruction”. | ++----------------------------------------------------+----------------------------------------------------+ + +The line number and last instruction in the traceback may differ from +the line number of its frame object if the exception occurred in a +"try" statement with no matching except clause or with a "finally" +clause. + +traceback.tb_next + + The special writable attribute "tb_next" is the next level in the + stack trace (towards the frame where the exception occurred), or + "None" if there is no next level. + + Changed in version 3.7: This attribute is now writable + + +Slice objects +------------- + +Slice objects are used to represent slices for "__getitem__()" +methods. They are also created by the built-in "slice()" function. + +Special read-only attributes: "start" is the lower bound; "stop" is +the upper bound; "step" is the step value; each is "None" if omitted. +These attributes can have any type. + +Slice objects support one method: + +slice.indices(self, length) + + This method takes a single integer argument *length* and computes + information about the slice that the slice object would describe if + applied to a sequence of *length* items. It returns a tuple of + three integers; respectively these are the *start* and *stop* + indices and the *step* or stride length of the slice. Missing or + out-of-bounds indices are handled in a manner consistent with + regular slices. + + +Static method objects +--------------------- + +Static method objects provide a way of defeating the transformation of +function objects to method objects described above. A static method +object is a wrapper around any other object, usually a user-defined +method object. When a static method object is retrieved from a class +or a class instance, the object actually returned is the wrapped +object, which is not subject to any further transformation. Static +method objects are also callable. Static method objects are created by +the built-in "staticmethod()" constructor. + + +Class method objects +-------------------- + +A class method object, like a static method object, is a wrapper +around another object that alters the way in which that object is +retrieved from classes and class instances. The behaviour of class +method objects upon such retrieval is described above, under “instance +methods”. Class method objects are created by the built-in +"classmethod()" constructor. +''', + 'typesfunctions': r'''Functions +********* + +Function objects are created by function definitions. The only +operation on a function object is to call it: "func(argument-list)". + +There are really two flavors of function objects: built-in functions +and user-defined functions. Both support the same operation (to call +the function), but the implementation is different, hence the +different object types. + +See Function definitions for more information. +''', + 'typesmapping': r'''Mapping Types — "dict" +********************** + +A *mapping* object maps *hashable* values to arbitrary objects. +Mappings are mutable objects. There is currently only one standard +mapping type, the *dictionary*. (For other containers see the built- +in "list", "set", and "tuple" classes, and the "collections" module.) + +A dictionary’s keys are *almost* arbitrary values. Values that are +not *hashable*, that is, values containing lists, dictionaries or +other mutable types (that are compared by value rather than by object +identity) may not be used as keys. Values that compare equal (such as +"1", "1.0", and "True") can be used interchangeably to index the same +dictionary entry. + +class dict(**kwargs) +class dict(mapping, **kwargs) +class dict(iterable, **kwargs) + + Return a new dictionary initialized from an optional positional + argument and a possibly empty set of keyword arguments. + + Dictionaries can be created by several means: + + * Use a comma-separated list of "key: value" pairs within braces: + "{'jack': 4098, 'sjoerd': 4127}" or "{4098: 'jack', 4127: + 'sjoerd'}" + + * Use a dict comprehension: "{}", "{x: x ** 2 for x in range(10)}" + + * Use the type constructor: "dict()", "dict([('foo', 100), ('bar', + 200)])", "dict(foo=100, bar=200)" + + If no positional argument is given, an empty dictionary is created. + If a positional argument is given and it defines a "keys()" method, + a dictionary is created by calling "__getitem__()" on the argument + with each returned key from the method. Otherwise, the positional + argument must be an *iterable* object. Each item in the iterable + must itself be an iterable with exactly two elements. The first + element of each item becomes a key in the new dictionary, and the + second element the corresponding value. If a key occurs more than + once, the last value for that key becomes the corresponding value + in the new dictionary. + + If keyword arguments are given, the keyword arguments and their + values are added to the dictionary created from the positional + argument. If a key being added is already present, the value from + the keyword argument replaces the value from the positional + argument. + + To illustrate, the following examples all return a dictionary equal + to "{"one": 1, "two": 2, "three": 3}": + + >>> a = dict(one=1, two=2, three=3) + >>> b = {'one': 1, 'two': 2, 'three': 3} + >>> c = dict(zip(['one', 'two', 'three'], [1, 2, 3])) + >>> d = dict([('two', 2), ('one', 1), ('three', 3)]) + >>> e = dict({'three': 3, 'one': 1, 'two': 2}) + >>> f = dict({'one': 1, 'three': 3}, two=2) + >>> a == b == c == d == e == f + True + + Providing keyword arguments as in the first example only works for + keys that are valid Python identifiers. Otherwise, any valid keys + can be used. + + These are the operations that dictionaries support (and therefore, + custom mapping types should support too): + + list(d) + + Return a list of all the keys used in the dictionary *d*. + + len(d) + + Return the number of items in the dictionary *d*. + + d[key] + + Return the item of *d* with key *key*. Raises a "KeyError" if + *key* is not in the map. + + If a subclass of dict defines a method "__missing__()" and *key* + is not present, the "d[key]" operation calls that method with + the key *key* as argument. The "d[key]" operation then returns + or raises whatever is returned or raised by the + "__missing__(key)" call. No other operations or methods invoke + "__missing__()". If "__missing__()" is not defined, "KeyError" + is raised. "__missing__()" must be a method; it cannot be an + instance variable: + + >>> class Counter(dict): + ... def __missing__(self, key): + ... return 0 + ... + >>> c = Counter() + >>> c['red'] + 0 + >>> c['red'] += 1 + >>> c['red'] + 1 + + The example above shows part of the implementation of + "collections.Counter". A different "__missing__" method is used + by "collections.defaultdict". + + d[key] = value + + Set "d[key]" to *value*. + + del d[key] + + Remove "d[key]" from *d*. Raises a "KeyError" if *key* is not + in the map. + + key in d + + Return "True" if *d* has a key *key*, else "False". + + key not in d + + Equivalent to "not key in d". + + iter(d) + + Return an iterator over the keys of the dictionary. This is a + shortcut for "iter(d.keys())". + + clear() + + Remove all items from the dictionary. + + copy() + + Return a shallow copy of the dictionary. + + classmethod fromkeys(iterable, value=None, /) + + Create a new dictionary with keys from *iterable* and values set + to *value*. + + "fromkeys()" is a class method that returns a new dictionary. + *value* defaults to "None". All of the values refer to just a + single instance, so it generally doesn’t make sense for *value* + to be a mutable object such as an empty list. To get distinct + values, use a dict comprehension instead. + + get(key, default=None) + + Return the value for *key* if *key* is in the dictionary, else + *default*. If *default* is not given, it defaults to "None", so + that this method never raises a "KeyError". + + items() + + Return a new view of the dictionary’s items ("(key, value)" + pairs). See the documentation of view objects. + + keys() + + Return a new view of the dictionary’s keys. See the + documentation of view objects. + + pop(key[, default]) + + If *key* is in the dictionary, remove it and return its value, + else return *default*. If *default* is not given and *key* is + not in the dictionary, a "KeyError" is raised. + + popitem() + + Remove and return a "(key, value)" pair from the dictionary. + Pairs are returned in LIFO (last-in, first-out) order. + + "popitem()" is useful to destructively iterate over a + dictionary, as often used in set algorithms. If the dictionary + is empty, calling "popitem()" raises a "KeyError". + + Changed in version 3.7: LIFO order is now guaranteed. In prior + versions, "popitem()" would return an arbitrary key/value pair. + + reversed(d) + + Return a reverse iterator over the keys of the dictionary. This + is a shortcut for "reversed(d.keys())". + + Added in version 3.8. + + setdefault(key, default=None) + + If *key* is in the dictionary, return its value. If not, insert + *key* with a value of *default* and return *default*. *default* + defaults to "None". + + update([other]) + + Update the dictionary with the key/value pairs from *other*, + overwriting existing keys. Return "None". + + "update()" accepts either another object with a "keys()" method + (in which case "__getitem__()" is called with every key returned + from the method) or an iterable of key/value pairs (as tuples or + other iterables of length two). If keyword arguments are + specified, the dictionary is then updated with those key/value + pairs: "d.update(red=1, blue=2)". + + values() + + Return a new view of the dictionary’s values. See the + documentation of view objects. + + An equality comparison between one "dict.values()" view and + another will always return "False". This also applies when + comparing "dict.values()" to itself: + + >>> d = {'a': 1} + >>> d.values() == d.values() + False + + d | other + + Create a new dictionary with the merged keys and values of *d* + and *other*, which must both be dictionaries. The values of + *other* take priority when *d* and *other* share keys. + + Added in version 3.9. + + d |= other + + Update the dictionary *d* with keys and values from *other*, + which may be either a *mapping* or an *iterable* of key/value + pairs. The values of *other* take priority when *d* and *other* + share keys. + + Added in version 3.9. + + Dictionaries compare equal if and only if they have the same "(key, + value)" pairs (regardless of ordering). Order comparisons (‘<’, + ‘<=’, ‘>=’, ‘>’) raise "TypeError". + + Dictionaries preserve insertion order. Note that updating a key + does not affect the order. Keys added after deletion are inserted + at the end. + + >>> d = {"one": 1, "two": 2, "three": 3, "four": 4} + >>> d + {'one': 1, 'two': 2, 'three': 3, 'four': 4} + >>> list(d) + ['one', 'two', 'three', 'four'] + >>> list(d.values()) + [1, 2, 3, 4] + >>> d["one"] = 42 + >>> d + {'one': 42, 'two': 2, 'three': 3, 'four': 4} + >>> del d["two"] + >>> d["two"] = None + >>> d + {'one': 42, 'three': 3, 'four': 4, 'two': None} + + Changed in version 3.7: Dictionary order is guaranteed to be + insertion order. This behavior was an implementation detail of + CPython from 3.6. + + Dictionaries and dictionary views are reversible. + + >>> d = {"one": 1, "two": 2, "three": 3, "four": 4} + >>> d + {'one': 1, 'two': 2, 'three': 3, 'four': 4} + >>> list(reversed(d)) + ['four', 'three', 'two', 'one'] + >>> list(reversed(d.values())) + [4, 3, 2, 1] + >>> list(reversed(d.items())) + [('four', 4), ('three', 3), ('two', 2), ('one', 1)] + + Changed in version 3.8: Dictionaries are now reversible. + +See also: + + "types.MappingProxyType" can be used to create a read-only view of a + "dict". + + +Dictionary view objects +======================= + +The objects returned by "dict.keys()", "dict.values()" and +"dict.items()" are *view objects*. They provide a dynamic view on the +dictionary’s entries, which means that when the dictionary changes, +the view reflects these changes. + +Dictionary views can be iterated over to yield their respective data, +and support membership tests: + +len(dictview) + + Return the number of entries in the dictionary. + +iter(dictview) + + Return an iterator over the keys, values or items (represented as + tuples of "(key, value)") in the dictionary. + + Keys and values are iterated over in insertion order. This allows + the creation of "(value, key)" pairs using "zip()": "pairs = + zip(d.values(), d.keys())". Another way to create the same list is + "pairs = [(v, k) for (k, v) in d.items()]". + + Iterating views while adding or deleting entries in the dictionary + may raise a "RuntimeError" or fail to iterate over all entries. + + Changed in version 3.7: Dictionary order is guaranteed to be + insertion order. + +x in dictview + + Return "True" if *x* is in the underlying dictionary’s keys, values + or items (in the latter case, *x* should be a "(key, value)" + tuple). + +reversed(dictview) + + Return a reverse iterator over the keys, values or items of the + dictionary. The view will be iterated in reverse order of the + insertion. + + Changed in version 3.8: Dictionary views are now reversible. + +dictview.mapping + + Return a "types.MappingProxyType" that wraps the original + dictionary to which the view refers. + + Added in version 3.10. + +Keys views are set-like since their entries are unique and *hashable*. +Items views also have set-like operations since the (key, value) pairs +are unique and the keys are hashable. If all values in an items view +are hashable as well, then the items view can interoperate with other +sets. (Values views are not treated as set-like since the entries are +generally not unique.) For set-like views, all of the operations +defined for the abstract base class "collections.abc.Set" are +available (for example, "==", "<", or "^"). While using set +operators, set-like views accept any iterable as the other operand, +unlike sets which only accept sets as the input. + +An example of dictionary view usage: + + >>> dishes = {'eggs': 2, 'sausage': 1, 'bacon': 1, 'spam': 500} + >>> keys = dishes.keys() + >>> values = dishes.values() + + >>> # iteration + >>> n = 0 + >>> for val in values: + ... n += val + ... + >>> print(n) + 504 + + >>> # keys and values are iterated over in the same order (insertion order) + >>> list(keys) + ['eggs', 'sausage', 'bacon', 'spam'] + >>> list(values) + [2, 1, 1, 500] + + >>> # view objects are dynamic and reflect dict changes + >>> del dishes['eggs'] + >>> del dishes['sausage'] + >>> list(keys) + ['bacon', 'spam'] + + >>> # set operations + >>> keys & {'eggs', 'bacon', 'salad'} + {'bacon'} + >>> keys ^ {'sausage', 'juice'} == {'juice', 'sausage', 'bacon', 'spam'} + True + >>> keys | ['juice', 'juice', 'juice'] == {'bacon', 'spam', 'juice'} + True + + >>> # get back a read-only proxy for the original dictionary + >>> values.mapping + mappingproxy({'bacon': 1, 'spam': 500}) + >>> values.mapping['spam'] + 500 +''', + 'typesmethods': r'''Methods +******* + +Methods are functions that are called using the attribute notation. +There are two flavors: built-in methods (such as "append()" on lists) +and class instance method. Built-in methods are described with the +types that support them. + +If you access a method (a function defined in a class namespace) +through an instance, you get a special object: a *bound method* (also +called instance method) object. When called, it will add the "self" +argument to the argument list. Bound methods have two special read- +only attributes: "m.__self__" is the object on which the method +operates, and "m.__func__" is the function implementing the method. +Calling "m(arg-1, arg-2, ..., arg-n)" is completely equivalent to +calling "m.__func__(m.__self__, arg-1, arg-2, ..., arg-n)". + +Like function objects, bound method objects support getting arbitrary +attributes. However, since method attributes are actually stored on +the underlying function object ("method.__func__"), setting method +attributes on bound methods is disallowed. Attempting to set an +attribute on a method results in an "AttributeError" being raised. In +order to set a method attribute, you need to explicitly set it on the +underlying function object: + + >>> class C: + ... def method(self): + ... pass + ... + >>> c = C() + >>> c.method.whoami = 'my name is method' # can't set on the method + Traceback (most recent call last): + File "<stdin>", line 1, in <module> + AttributeError: 'method' object has no attribute 'whoami' + >>> c.method.__func__.whoami = 'my name is method' + >>> c.method.whoami + 'my name is method' + +See Instance methods for more information. +''', + 'typesmodules': r'''Modules +******* + +The only special operation on a module is attribute access: "m.name", +where *m* is a module and *name* accesses a name defined in *m*’s +symbol table. Module attributes can be assigned to. (Note that the +"import" statement is not, strictly speaking, an operation on a module +object; "import foo" does not require a module object named *foo* to +exist, rather it requires an (external) *definition* for a module +named *foo* somewhere.) + +A special attribute of every module is "__dict__". This is the +dictionary containing the module’s symbol table. Modifying this +dictionary will actually change the module’s symbol table, but direct +assignment to the "__dict__" attribute is not possible (you can write +"m.__dict__['a'] = 1", which defines "m.a" to be "1", but you can’t +write "m.__dict__ = {}"). Modifying "__dict__" directly is not +recommended. + +Modules built into the interpreter are written like this: "<module +'sys' (built-in)>". If loaded from a file, they are written as +"<module 'os' from '/usr/local/lib/pythonX.Y/os.pyc'>". +''', + 'typesseq': r'''Sequence Types — "list", "tuple", "range" +***************************************** + +There are three basic sequence types: lists, tuples, and range +objects. Additional sequence types tailored for processing of binary +data and text strings are described in dedicated sections. + + +Common Sequence Operations +========================== + +The operations in the following table are supported by most sequence +types, both mutable and immutable. The "collections.abc.Sequence" ABC +is provided to make it easier to correctly implement these operations +on custom sequence types. + +This table lists the sequence operations sorted in ascending priority. +In the table, *s* and *t* are sequences of the same type, *n*, *i*, +*j* and *k* are integers and *x* is an arbitrary object that meets any +type and value restrictions imposed by *s*. + +The "in" and "not in" operations have the same priorities as the +comparison operations. The "+" (concatenation) and "*" (repetition) +operations have the same priority as the corresponding numeric +operations. [3] + ++----------------------------+----------------------------------+------------+ +| Operation | Result | Notes | +|============================|==================================|============| +| "x in s" | "True" if an item of *s* is | (1) | +| | equal to *x*, else "False" | | ++----------------------------+----------------------------------+------------+ +| "x not in s" | "False" if an item of *s* is | (1) | +| | equal to *x*, else "True" | | ++----------------------------+----------------------------------+------------+ +| "s + t" | the concatenation of *s* and *t* | (6)(7) | ++----------------------------+----------------------------------+------------+ +| "s * n" or "n * s" | equivalent to adding *s* to | (2)(7) | +| | itself *n* times | | ++----------------------------+----------------------------------+------------+ +| "s[i]" | *i*th item of *s*, origin 0 | (3) | ++----------------------------+----------------------------------+------------+ +| "s[i:j]" | slice of *s* from *i* to *j* | (3)(4) | ++----------------------------+----------------------------------+------------+ +| "s[i:j:k]" | slice of *s* from *i* to *j* | (3)(5) | +| | with step *k* | | ++----------------------------+----------------------------------+------------+ +| "len(s)" | length of *s* | | ++----------------------------+----------------------------------+------------+ +| "min(s)" | smallest item of *s* | | ++----------------------------+----------------------------------+------------+ +| "max(s)" | largest item of *s* | | ++----------------------------+----------------------------------+------------+ +| "s.index(x[, i[, j]])" | index of the first occurrence of | (8) | +| | *x* in *s* (at or after index | | +| | *i* and before index *j*) | | ++----------------------------+----------------------------------+------------+ +| "s.count(x)" | total number of occurrences of | | +| | *x* in *s* | | ++----------------------------+----------------------------------+------------+ + +Sequences of the same type also support comparisons. In particular, +tuples and lists are compared lexicographically by comparing +corresponding elements. This means that to compare equal, every +element must compare equal and the two sequences must be of the same +type and have the same length. (For full details see Comparisons in +the language reference.) + +Forward and reversed iterators over mutable sequences access values +using an index. That index will continue to march forward (or +backward) even if the underlying sequence is mutated. The iterator +terminates only when an "IndexError" or a "StopIteration" is +encountered (or when the index drops below zero). + +Notes: + +1. While the "in" and "not in" operations are used only for simple + containment testing in the general case, some specialised sequences + (such as "str", "bytes" and "bytearray") also use them for + subsequence testing: + + >>> "gg" in "eggs" + True + +2. Values of *n* less than "0" are treated as "0" (which yields an + empty sequence of the same type as *s*). Note that items in the + sequence *s* are not copied; they are referenced multiple times. + This often haunts new Python programmers; consider: + + >>> lists = [[]] * 3 + >>> lists + [[], [], []] + >>> lists[0].append(3) + >>> lists + [[3], [3], [3]] + + What has happened is that "[[]]" is a one-element list containing + an empty list, so all three elements of "[[]] * 3" are references + to this single empty list. Modifying any of the elements of + "lists" modifies this single list. You can create a list of + different lists this way: + + >>> lists = [[] for i in range(3)] + >>> lists[0].append(3) + >>> lists[1].append(5) + >>> lists[2].append(7) + >>> lists + [[3], [5], [7]] + + Further explanation is available in the FAQ entry How do I create a + multidimensional list?. + +3. If *i* or *j* is negative, the index is relative to the end of + sequence *s*: "len(s) + i" or "len(s) + j" is substituted. But + note that "-0" is still "0". + +4. The slice of *s* from *i* to *j* is defined as the sequence of + items with index *k* such that "i <= k < j". If *i* or *j* is + greater than "len(s)", use "len(s)". If *i* is omitted or "None", + use "0". If *j* is omitted or "None", use "len(s)". If *i* is + greater than or equal to *j*, the slice is empty. + +5. The slice of *s* from *i* to *j* with step *k* is defined as the + sequence of items with index "x = i + n*k" such that "0 <= n < + (j-i)/k". In other words, the indices are "i", "i+k", "i+2*k", + "i+3*k" and so on, stopping when *j* is reached (but never + including *j*). When *k* is positive, *i* and *j* are reduced to + "len(s)" if they are greater. When *k* is negative, *i* and *j* are + reduced to "len(s) - 1" if they are greater. If *i* or *j* are + omitted or "None", they become “end” values (which end depends on + the sign of *k*). Note, *k* cannot be zero. If *k* is "None", it + is treated like "1". + +6. Concatenating immutable sequences always results in a new object. + This means that building up a sequence by repeated concatenation + will have a quadratic runtime cost in the total sequence length. + To get a linear runtime cost, you must switch to one of the + alternatives below: + + * if concatenating "str" objects, you can build a list and use + "str.join()" at the end or else write to an "io.StringIO" + instance and retrieve its value when complete + + * if concatenating "bytes" objects, you can similarly use + "bytes.join()" or "io.BytesIO", or you can do in-place + concatenation with a "bytearray" object. "bytearray" objects are + mutable and have an efficient overallocation mechanism + + * if concatenating "tuple" objects, extend a "list" instead + + * for other types, investigate the relevant class documentation + +7. Some sequence types (such as "range") only support item sequences + that follow specific patterns, and hence don’t support sequence + concatenation or repetition. + +8. "index" raises "ValueError" when *x* is not found in *s*. Not all + implementations support passing the additional arguments *i* and + *j*. These arguments allow efficient searching of subsections of + the sequence. Passing the extra arguments is roughly equivalent to + using "s[i:j].index(x)", only without copying any data and with the + returned index being relative to the start of the sequence rather + than the start of the slice. + + +Immutable Sequence Types +======================== + +The only operation that immutable sequence types generally implement +that is not also implemented by mutable sequence types is support for +the "hash()" built-in. + +This support allows immutable sequences, such as "tuple" instances, to +be used as "dict" keys and stored in "set" and "frozenset" instances. + +Attempting to hash an immutable sequence that contains unhashable +values will result in "TypeError". + + +Mutable Sequence Types +====================== + +The operations in the following table are defined on mutable sequence +types. The "collections.abc.MutableSequence" ABC is provided to make +it easier to correctly implement these operations on custom sequence +types. + +In the table *s* is an instance of a mutable sequence type, *t* is any +iterable object and *x* is an arbitrary object that meets any type and +value restrictions imposed by *s* (for example, "bytearray" only +accepts integers that meet the value restriction "0 <= x <= 255"). + ++--------------------------------+----------------------------------+-----------------------+ +| Operation | Result | Notes | +|================================|==================================|=======================| +| "s[i] = x" | item *i* of *s* is replaced by | | +| | *x* | | ++--------------------------------+----------------------------------+-----------------------+ +| "s[i:j] = t" | slice of *s* from *i* to *j* is | | +| | replaced by the contents of the | | +| | iterable *t* | | ++--------------------------------+----------------------------------+-----------------------+ +| "del s[i:j]" | same as "s[i:j] = []" | | ++--------------------------------+----------------------------------+-----------------------+ +| "s[i:j:k] = t" | the elements of "s[i:j:k]" are | (1) | +| | replaced by those of *t* | | ++--------------------------------+----------------------------------+-----------------------+ +| "del s[i:j:k]" | removes the elements of | | +| | "s[i:j:k]" from the list | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.append(x)" | appends *x* to the end of the | | +| | sequence (same as | | +| | "s[len(s):len(s)] = [x]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.clear()" | removes all items from *s* (same | (5) | +| | as "del s[:]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.copy()" | creates a shallow copy of *s* | (5) | +| | (same as "s[:]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.extend(t)" or "s += t" | extends *s* with the contents of | | +| | *t* (for the most part the same | | +| | as "s[len(s):len(s)] = t") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s *= n" | updates *s* with its contents | (6) | +| | repeated *n* times | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.insert(i, x)" | inserts *x* into *s* at the | | +| | index given by *i* (same as | | +| | "s[i:i] = [x]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.pop()" or "s.pop(i)" | retrieves the item at *i* and | (2) | +| | also removes it from *s* | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.remove(x)" | removes the first item from *s* | (3) | +| | where "s[i]" is equal to *x* | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.reverse()" | reverses the items of *s* in | (4) | +| | place | | ++--------------------------------+----------------------------------+-----------------------+ + +Notes: + +1. If *k* is not equal to "1", *t* must have the same length as the + slice it is replacing. + +2. The optional argument *i* defaults to "-1", so that by default the + last item is removed and returned. + +3. "remove()" raises "ValueError" when *x* is not found in *s*. + +4. The "reverse()" method modifies the sequence in place for economy + of space when reversing a large sequence. To remind users that it + operates by side effect, it does not return the reversed sequence. + +5. "clear()" and "copy()" are included for consistency with the + interfaces of mutable containers that don’t support slicing + operations (such as "dict" and "set"). "copy()" is not part of the + "collections.abc.MutableSequence" ABC, but most concrete mutable + sequence classes provide it. + + Added in version 3.3: "clear()" and "copy()" methods. + +6. The value *n* is an integer, or an object implementing + "__index__()". Zero and negative values of *n* clear the sequence. + Items in the sequence are not copied; they are referenced multiple + times, as explained for "s * n" under Common Sequence Operations. + + +Lists +===== + +Lists are mutable sequences, typically used to store collections of +homogeneous items (where the precise degree of similarity will vary by +application). + +class list([iterable]) + + Lists may be constructed in several ways: + + * Using a pair of square brackets to denote the empty list: "[]" + + * Using square brackets, separating items with commas: "[a]", "[a, + b, c]" + + * Using a list comprehension: "[x for x in iterable]" + + * Using the type constructor: "list()" or "list(iterable)" + + The constructor builds a list whose items are the same and in the + same order as *iterable*’s items. *iterable* may be either a + sequence, a container that supports iteration, or an iterator + object. If *iterable* is already a list, a copy is made and + returned, similar to "iterable[:]". For example, "list('abc')" + returns "['a', 'b', 'c']" and "list( (1, 2, 3) )" returns "[1, 2, + 3]". If no argument is given, the constructor creates a new empty + list, "[]". + + Many other operations also produce lists, including the "sorted()" + built-in. + + Lists implement all of the common and mutable sequence operations. + Lists also provide the following additional method: + + sort(*, key=None, reverse=False) + + This method sorts the list in place, using only "<" comparisons + between items. Exceptions are not suppressed - if any comparison + operations fail, the entire sort operation will fail (and the + list will likely be left in a partially modified state). + + "sort()" accepts two arguments that can only be passed by + keyword (keyword-only arguments): + + *key* specifies a function of one argument that is used to + extract a comparison key from each list element (for example, + "key=str.lower"). The key corresponding to each item in the list + is calculated once and then used for the entire sorting process. + The default value of "None" means that list items are sorted + directly without calculating a separate key value. + + The "functools.cmp_to_key()" utility is available to convert a + 2.x style *cmp* function to a *key* function. + + *reverse* is a boolean value. If set to "True", then the list + elements are sorted as if each comparison were reversed. + + This method modifies the sequence in place for economy of space + when sorting a large sequence. To remind users that it operates + by side effect, it does not return the sorted sequence (use + "sorted()" to explicitly request a new sorted list instance). + + The "sort()" method is guaranteed to be stable. A sort is + stable if it guarantees not to change the relative order of + elements that compare equal — this is helpful for sorting in + multiple passes (for example, sort by department, then by salary + grade). + + For sorting examples and a brief sorting tutorial, see Sorting + Techniques. + + **CPython implementation detail:** While a list is being sorted, + the effect of attempting to mutate, or even inspect, the list is + undefined. The C implementation of Python makes the list appear + empty for the duration, and raises "ValueError" if it can detect + that the list has been mutated during a sort. + + +Tuples +====== + +Tuples are immutable sequences, typically used to store collections of +heterogeneous data (such as the 2-tuples produced by the "enumerate()" +built-in). Tuples are also used for cases where an immutable sequence +of homogeneous data is needed (such as allowing storage in a "set" or +"dict" instance). + +class tuple([iterable]) + + Tuples may be constructed in a number of ways: + + * Using a pair of parentheses to denote the empty tuple: "()" + + * Using a trailing comma for a singleton tuple: "a," or "(a,)" + + * Separating items with commas: "a, b, c" or "(a, b, c)" + + * Using the "tuple()" built-in: "tuple()" or "tuple(iterable)" + + The constructor builds a tuple whose items are the same and in the + same order as *iterable*’s items. *iterable* may be either a + sequence, a container that supports iteration, or an iterator + object. If *iterable* is already a tuple, it is returned + unchanged. For example, "tuple('abc')" returns "('a', 'b', 'c')" + and "tuple( [1, 2, 3] )" returns "(1, 2, 3)". If no argument is + given, the constructor creates a new empty tuple, "()". + + Note that it is actually the comma which makes a tuple, not the + parentheses. The parentheses are optional, except in the empty + tuple case, or when they are needed to avoid syntactic ambiguity. + For example, "f(a, b, c)" is a function call with three arguments, + while "f((a, b, c))" is a function call with a 3-tuple as the sole + argument. + + Tuples implement all of the common sequence operations. + +For heterogeneous collections of data where access by name is clearer +than access by index, "collections.namedtuple()" may be a more +appropriate choice than a simple tuple object. + + +Ranges +====== + +The "range" type represents an immutable sequence of numbers and is +commonly used for looping a specific number of times in "for" loops. + +class range(stop) +class range(start, stop[, step]) + + The arguments to the range constructor must be integers (either + built-in "int" or any object that implements the "__index__()" + special method). If the *step* argument is omitted, it defaults to + "1". If the *start* argument is omitted, it defaults to "0". If + *step* is zero, "ValueError" is raised. + + For a positive *step*, the contents of a range "r" are determined + by the formula "r[i] = start + step*i" where "i >= 0" and "r[i] < + stop". + + For a negative *step*, the contents of the range are still + determined by the formula "r[i] = start + step*i", but the + constraints are "i >= 0" and "r[i] > stop". + + A range object will be empty if "r[0]" does not meet the value + constraint. Ranges do support negative indices, but these are + interpreted as indexing from the end of the sequence determined by + the positive indices. + + Ranges containing absolute values larger than "sys.maxsize" are + permitted but some features (such as "len()") may raise + "OverflowError". + + Range examples: + + >>> list(range(10)) + [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] + >>> list(range(1, 11)) + [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] + >>> list(range(0, 30, 5)) + [0, 5, 10, 15, 20, 25] + >>> list(range(0, 10, 3)) + [0, 3, 6, 9] + >>> list(range(0, -10, -1)) + [0, -1, -2, -3, -4, -5, -6, -7, -8, -9] + >>> list(range(0)) + [] + >>> list(range(1, 0)) + [] + + Ranges implement all of the common sequence operations except + concatenation and repetition (due to the fact that range objects + can only represent sequences that follow a strict pattern and + repetition and concatenation will usually violate that pattern). + + start + + The value of the *start* parameter (or "0" if the parameter was + not supplied) + + stop + + The value of the *stop* parameter + + step + + The value of the *step* parameter (or "1" if the parameter was + not supplied) + +The advantage of the "range" type over a regular "list" or "tuple" is +that a "range" object will always take the same (small) amount of +memory, no matter the size of the range it represents (as it only +stores the "start", "stop" and "step" values, calculating individual +items and subranges as needed). + +Range objects implement the "collections.abc.Sequence" ABC, and +provide features such as containment tests, element index lookup, +slicing and support for negative indices (see Sequence Types — list, +tuple, range): + +>>> r = range(0, 20, 2) +>>> r +range(0, 20, 2) +>>> 11 in r +False +>>> 10 in r +True +>>> r.index(10) +5 +>>> r[5] +10 +>>> r[:5] +range(0, 10, 2) +>>> r[-1] +18 + +Testing range objects for equality with "==" and "!=" compares them as +sequences. That is, two range objects are considered equal if they +represent the same sequence of values. (Note that two range objects +that compare equal might have different "start", "stop" and "step" +attributes, for example "range(0) == range(2, 1, 3)" or "range(0, 3, +2) == range(0, 4, 2)".) + +Changed in version 3.2: Implement the Sequence ABC. Support slicing +and negative indices. Test "int" objects for membership in constant +time instead of iterating through all items. + +Changed in version 3.3: Define ‘==’ and ‘!=’ to compare range objects +based on the sequence of values they define (instead of comparing +based on object identity).Added the "start", "stop" and "step" +attributes. + +See also: + + * The linspace recipe shows how to implement a lazy version of range + suitable for floating-point applications. +''', + 'typesseq-mutable': r'''Mutable Sequence Types +********************** + +The operations in the following table are defined on mutable sequence +types. The "collections.abc.MutableSequence" ABC is provided to make +it easier to correctly implement these operations on custom sequence +types. + +In the table *s* is an instance of a mutable sequence type, *t* is any +iterable object and *x* is an arbitrary object that meets any type and +value restrictions imposed by *s* (for example, "bytearray" only +accepts integers that meet the value restriction "0 <= x <= 255"). + ++--------------------------------+----------------------------------+-----------------------+ +| Operation | Result | Notes | +|================================|==================================|=======================| +| "s[i] = x" | item *i* of *s* is replaced by | | +| | *x* | | ++--------------------------------+----------------------------------+-----------------------+ +| "s[i:j] = t" | slice of *s* from *i* to *j* is | | +| | replaced by the contents of the | | +| | iterable *t* | | ++--------------------------------+----------------------------------+-----------------------+ +| "del s[i:j]" | same as "s[i:j] = []" | | ++--------------------------------+----------------------------------+-----------------------+ +| "s[i:j:k] = t" | the elements of "s[i:j:k]" are | (1) | +| | replaced by those of *t* | | ++--------------------------------+----------------------------------+-----------------------+ +| "del s[i:j:k]" | removes the elements of | | +| | "s[i:j:k]" from the list | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.append(x)" | appends *x* to the end of the | | +| | sequence (same as | | +| | "s[len(s):len(s)] = [x]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.clear()" | removes all items from *s* (same | (5) | +| | as "del s[:]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.copy()" | creates a shallow copy of *s* | (5) | +| | (same as "s[:]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.extend(t)" or "s += t" | extends *s* with the contents of | | +| | *t* (for the most part the same | | +| | as "s[len(s):len(s)] = t") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s *= n" | updates *s* with its contents | (6) | +| | repeated *n* times | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.insert(i, x)" | inserts *x* into *s* at the | | +| | index given by *i* (same as | | +| | "s[i:i] = [x]") | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.pop()" or "s.pop(i)" | retrieves the item at *i* and | (2) | +| | also removes it from *s* | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.remove(x)" | removes the first item from *s* | (3) | +| | where "s[i]" is equal to *x* | | ++--------------------------------+----------------------------------+-----------------------+ +| "s.reverse()" | reverses the items of *s* in | (4) | +| | place | | ++--------------------------------+----------------------------------+-----------------------+ + +Notes: + +1. If *k* is not equal to "1", *t* must have the same length as the + slice it is replacing. + +2. The optional argument *i* defaults to "-1", so that by default the + last item is removed and returned. + +3. "remove()" raises "ValueError" when *x* is not found in *s*. + +4. The "reverse()" method modifies the sequence in place for economy + of space when reversing a large sequence. To remind users that it + operates by side effect, it does not return the reversed sequence. + +5. "clear()" and "copy()" are included for consistency with the + interfaces of mutable containers that don’t support slicing + operations (such as "dict" and "set"). "copy()" is not part of the + "collections.abc.MutableSequence" ABC, but most concrete mutable + sequence classes provide it. + + Added in version 3.3: "clear()" and "copy()" methods. + +6. The value *n* is an integer, or an object implementing + "__index__()". Zero and negative values of *n* clear the sequence. + Items in the sequence are not copied; they are referenced multiple + times, as explained for "s * n" under Common Sequence Operations. +''', + 'unary': r'''Unary arithmetic and bitwise operations +*************************************** + +All unary arithmetic and bitwise operations have the same priority: + + u_expr ::= power | "-" u_expr | "+" u_expr | "~" u_expr + +The unary "-" (minus) operator yields the negation of its numeric +argument; the operation can be overridden with the "__neg__()" special +method. + +The unary "+" (plus) operator yields its numeric argument unchanged; +the operation can be overridden with the "__pos__()" special method. + +The unary "~" (invert) operator yields the bitwise inversion of its +integer argument. The bitwise inversion of "x" is defined as +"-(x+1)". It only applies to integral numbers or to custom objects +that override the "__invert__()" special method. + +In all three cases, if the argument does not have the proper type, a +"TypeError" exception is raised. +''', + 'while': r'''The "while" statement +********************* + +The "while" statement is used for repeated execution as long as an +expression is true: + + while_stmt ::= "while" assignment_expression ":" suite + ["else" ":" suite] + +This repeatedly tests the expression and, if it is true, executes the +first suite; if the expression is false (which may be the first time +it is tested) the suite of the "else" clause, if present, is executed +and the loop terminates. + +A "break" statement executed in the first suite terminates the loop +without executing the "else" clause’s suite. A "continue" statement +executed in the first suite skips the rest of the suite and goes back +to testing the expression. +''', + 'with': r'''The "with" statement +******************** + +The "with" statement is used to wrap the execution of a block with +methods defined by a context manager (see section With Statement +Context Managers). This allows common "try"…"except"…"finally" usage +patterns to be encapsulated for convenient reuse. + + with_stmt ::= "with" ( "(" with_stmt_contents ","? ")" | with_stmt_contents ) ":" suite + with_stmt_contents ::= with_item ("," with_item)* + with_item ::= expression ["as" target] + +The execution of the "with" statement with one “item” proceeds as +follows: + +1. The context expression (the expression given in the "with_item") is + evaluated to obtain a context manager. + +2. The context manager’s "__enter__()" is loaded for later use. + +3. The context manager’s "__exit__()" is loaded for later use. + +4. The context manager’s "__enter__()" method is invoked. + +5. If a target was included in the "with" statement, the return value + from "__enter__()" is assigned to it. + + Note: + + The "with" statement guarantees that if the "__enter__()" method + returns without an error, then "__exit__()" will always be + called. Thus, if an error occurs during the assignment to the + target list, it will be treated the same as an error occurring + within the suite would be. See step 7 below. + +6. The suite is executed. + +7. The context manager’s "__exit__()" method is invoked. If an + exception caused the suite to be exited, its type, value, and + traceback are passed as arguments to "__exit__()". Otherwise, three + "None" arguments are supplied. + + If the suite was exited due to an exception, and the return value + from the "__exit__()" method was false, the exception is reraised. + If the return value was true, the exception is suppressed, and + execution continues with the statement following the "with" + statement. + + If the suite was exited for any reason other than an exception, the + return value from "__exit__()" is ignored, and execution proceeds + at the normal location for the kind of exit that was taken. + +The following code: + + with EXPRESSION as TARGET: + SUITE + +is semantically equivalent to: + + manager = (EXPRESSION) + enter = type(manager).__enter__ + exit = type(manager).__exit__ + value = enter(manager) + hit_except = False + + try: + TARGET = value + SUITE + except: + hit_except = True + if not exit(manager, *sys.exc_info()): + raise + finally: + if not hit_except: + exit(manager, None, None, None) + +With more than one item, the context managers are processed as if +multiple "with" statements were nested: + + with A() as a, B() as b: + SUITE + +is semantically equivalent to: + + with A() as a: + with B() as b: + SUITE + +You can also write multi-item context managers in multiple lines if +the items are surrounded by parentheses. For example: + + with ( + A() as a, + B() as b, + ): + SUITE + +Changed in version 3.1: Support for multiple context expressions. + +Changed in version 3.10: Support for using grouping parentheses to +break the statement in multiple lines. + +See also: + + **PEP 343** - The “with” statement + The specification, background, and examples for the Python "with" + statement. +''', + 'yield': r'''The "yield" statement +********************* + + yield_stmt ::= yield_expression + +A "yield" statement is semantically equivalent to a yield expression. +The "yield" statement can be used to omit the parentheses that would +otherwise be required in the equivalent yield expression statement. +For example, the yield statements + + yield <expr> + yield from <expr> + +are equivalent to the yield expression statements + + (yield <expr>) + (yield from <expr>) + +Yield expressions and statements are only used when defining a +*generator* function, and are only used in the body of the generator +function. Using "yield" in a function definition is sufficient to +cause that definition to create a generator function instead of a +normal function. + +For full details of "yield" semantics, refer to the Yield expressions +section. +''', +} |