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Diffstat (limited to 'Doc/library')
| -rw-r--r-- | Doc/library/archiving.rst | 4 | ||||
| -rw-r--r-- | Doc/library/base64.rst | 48 | ||||
| -rw-r--r-- | Doc/library/code.rst | 6 | ||||
| -rw-r--r-- | Doc/library/compression.rst | 18 | ||||
| -rw-r--r-- | Doc/library/compression.zstd.rst | 840 | ||||
| -rw-r--r-- | Doc/library/curses.rst | 10 | ||||
| -rw-r--r-- | Doc/library/datetime.rst | 14 | ||||
| -rw-r--r-- | Doc/library/decimal.rst | 72 | ||||
| -rw-r--r-- | Doc/library/functions.rst | 76 | ||||
| -rw-r--r-- | Doc/library/importlib.resources.abc.rst | 48 | ||||
| -rw-r--r-- | Doc/library/io.rst | 92 | ||||
| -rw-r--r-- | Doc/library/multiprocessing.rst | 12 | ||||
| -rw-r--r-- | Doc/library/pdb.rst | 20 | ||||
| -rw-r--r-- | Doc/library/re.rst | 16 | ||||
| -rw-r--r-- | Doc/library/signal.rst | 4 | ||||
| -rw-r--r-- | Doc/library/socket.rst | 10 | ||||
| -rw-r--r-- | Doc/library/socketserver.rst | 2 |
17 files changed, 1120 insertions, 172 deletions
diff --git a/Doc/library/archiving.rst b/Doc/library/archiving.rst index c9284949af4..da0b3f8c3e7 100644 --- a/Doc/library/archiving.rst +++ b/Doc/library/archiving.rst @@ -5,13 +5,15 @@ Data Compression and Archiving ****************************** The modules described in this chapter support data compression with the zlib, -gzip, bzip2 and lzma algorithms, and the creation of ZIP- and tar-format +gzip, bzip2, lzma, and zstd algorithms, and the creation of ZIP- and tar-format archives. See also :ref:`archiving-operations` provided by the :mod:`shutil` module. .. toctree:: + compression.rst + compression.zstd.rst zlib.rst gzip.rst bz2.rst diff --git a/Doc/library/base64.rst b/Doc/library/base64.rst index 834ab2536e6..529a7242443 100644 --- a/Doc/library/base64.rst +++ b/Doc/library/base64.rst @@ -15,14 +15,9 @@ This module provides functions for encoding binary data to printable ASCII characters and decoding such encodings back to binary data. -It provides encoding and decoding functions for the encodings specified in -:rfc:`4648`, which defines the Base16, Base32, and Base64 algorithms, -and for the de-facto standard Ascii85 and Base85 encodings. - -The :rfc:`4648` encodings are suitable for encoding binary data so that it can be -safely sent by email, used as parts of URLs, or included as part of an HTTP -POST request. The encoding algorithm is not the same as the -:program:`uuencode` program. +This includes the :ref:`encodings specified in <base64-rfc-4648>` +:rfc:`4648` (Base64, Base32 and Base16) +and the non-standard :ref:`Base85 encodings <base64-base-85>`. There are two interfaces provided by this module. The modern interface supports encoding :term:`bytes-like objects <bytes-like object>` to ASCII @@ -30,7 +25,7 @@ supports encoding :term:`bytes-like objects <bytes-like object>` to ASCII strings containing ASCII to :class:`bytes`. Both base-64 alphabets defined in :rfc:`4648` (normal, and URL- and filesystem-safe) are supported. -The legacy interface does not support decoding from strings, but it does +The :ref:`legacy interface <base64-legacy>` does not support decoding from strings, but it does provide functions for encoding and decoding to and from :term:`file objects <file object>`. It only supports the Base64 standard alphabet, and it adds newlines every 76 characters as per :rfc:`2045`. Note that if you are looking @@ -46,7 +41,15 @@ package instead. Any :term:`bytes-like objects <bytes-like object>` are now accepted by all encoding and decoding functions in this module. Ascii85/Base85 support added. -The modern interface provides: + +.. _base64-rfc-4648: + +RFC 4648 Encodings +------------------ + +The :rfc:`4648` encodings are suitable for encoding binary data so that it can be +safely sent by email, used as parts of URLs, or included as part of an HTTP +POST request. .. function:: b64encode(s, altchars=None) @@ -181,6 +184,26 @@ The modern interface provides: incorrectly padded or if there are non-alphabet characters present in the input. +.. _base64-base-85: + +Base85 Encodings +----------------- + +Base85 encoding is not formally specified but rather a de facto standard, +thus different systems perform the encoding differently. + +The :func:`a85encode` and :func:`b85encode` functions in this module are two implementations of +the de facto standard. You should call the function with the Base85 +implementation used by the software you intend to work with. + +The two functions present in this module differ in how they handle the following: + +* Whether to include enclosing ``<~`` and ``~>`` markers +* Whether to include newline characters +* The set of ASCII characters used for encoding +* Handling of null bytes + +Refer to the documentation of the individual functions for more information. .. function:: a85encode(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False) @@ -262,7 +285,10 @@ The modern interface provides: .. versionadded:: 3.13 -The legacy interface: +.. _base64-legacy: + +Legacy Interface +---------------- .. function:: decode(input, output) diff --git a/Doc/library/code.rst b/Doc/library/code.rst index 8f7692df9fb..52587c4dd8f 100644 --- a/Doc/library/code.rst +++ b/Doc/library/code.rst @@ -22,6 +22,12 @@ build applications which provide an interactive interpreter prompt. it defaults to a newly created dictionary with key ``'__name__'`` set to ``'__console__'`` and key ``'__doc__'`` set to ``None``. + Note that functions and classes objects created under an + :class:`!InteractiveInterpreter` instance will belong to the namespace + specified by *locals*. + They are only pickleable if *locals* is the namespace of an existing + module. + .. class:: InteractiveConsole(locals=None, filename="<console>", local_exit=False) diff --git a/Doc/library/compression.rst b/Doc/library/compression.rst new file mode 100644 index 00000000000..618b4a3c2bd --- /dev/null +++ b/Doc/library/compression.rst @@ -0,0 +1,18 @@ +The :mod:`!compression` package +=============================== + +.. versionadded:: 3.14 + +The :mod:`!compression` package contains the canonical compression modules +containing interfaces to several different compression algorithms. Some of +these modules have historically been available as separate modules; those will +continue to be available under their original names for compatibility reasons, +and will not be removed without a deprecation cycle. The use of modules in +:mod:`!compression` is encouraged where practical. + +* :mod:`!compression.bz2` -- Re-exports :mod:`bz2` +* :mod:`!compression.gzip` -- Re-exports :mod:`gzip` +* :mod:`!compression.lzma` -- Re-exports :mod:`lzma` +* :mod:`!compression.zlib` -- Re-exports :mod:`zlib` +* :mod:`compression.zstd` -- Wrapper for the Zstandard compression library + diff --git a/Doc/library/compression.zstd.rst b/Doc/library/compression.zstd.rst new file mode 100644 index 00000000000..1e1802155a1 --- /dev/null +++ b/Doc/library/compression.zstd.rst @@ -0,0 +1,840 @@ +:mod:`!compression.zstd` --- Compression compatible with the Zstandard format +============================================================================= + +.. module:: compression.zstd + :synopsis: Low-level interface to compression and decompression routines in + the zstd library. + +.. versionadded:: 3.14 + +**Source code:** :source:`Lib/compression/zstd/__init__.py` + +-------------- + +This module provides classes and functions for compressing and decompressing +data using the Zstandard (or *zstd*) compression algorithm. The +`zstd manual <https://facebook.github.io/zstd/doc/api_manual_latest.html>`__ +describes Zstandard as "a fast lossless compression algorithm, targeting +real-time compression scenarios at zlib-level and better compression ratios." +Also included is a file interface that supports reading and writing the +contents of ``.zst`` files created by the :program:`zstd` utility, as well as +raw zstd compressed streams. + +The :mod:`!compression.zstd` module contains: + +* The :func:`.open` function and :class:`ZstdFile` class for reading and + writing compressed files. +* The :class:`ZstdCompressor` and :class:`ZstdDecompressor` classes for + incremental (de)compression. +* The :func:`compress` and :func:`decompress` functions for one-shot + (de)compression. +* The :func:`train_dict` and :func:`finalize_dict` functions and the + :class:`ZstdDict` class to train and manage Zstandard dictionaries. +* The :class:`CompressionParameter`, :class:`DecompressionParameter`, and + :class:`Strategy` classes for setting advanced (de)compression parameters. + + +Exceptions +---------- + +.. exception:: ZstdError + + This exception is raised when an error occurs during compression or + decompression, or while initializing the (de)compressor state. + + +Reading and writing compressed files +------------------------------------ + +.. function:: open(file, /, mode='rb', *, level=None, options=None, \ + zstd_dict=None, encoding=None, errors=None, newline=None) + + Open a Zstandard-compressed file in binary or text mode, returning a + :term:`file object`. + + The *file* argument can be either a file name (given as a + :class:`str`, :class:`bytes` or :term:`path-like <path-like object>` + object), in which case the named file is opened, or it can be an existing + file object to read from or write to. + + The mode argument can be either ``'rb'`` for reading (default), ``'wb'`` for + overwriting, ``'ab'`` for appending, or ``'xb'`` for exclusive creation. + These can equivalently be given as ``'r'``, ``'w'``, ``'a'``, and ``'x'`` + respectively. You may also open in text mode with ``'rt'``, ``'wt'``, + ``'at'``, and ``'xt'`` respectively. + + When reading, the *options* argument can be a dictionary providing advanced + decompression parameters; see :class:`DecompressionParameter` for detailed + information about supported + parameters. The *zstd_dict* argument is a :class:`ZstdDict` instance to be + used during decompression. When reading, if the *level* + argument is not None, a :exc:`!TypeError` will be raised. + + When writing, the *options* argument can be a dictionary + providing advanced decompression parameters; see + :class:`CompressionParameter` for detailed information about supported + parameters. The *level* argument is the compression level to use when + writing compressed data. Only one of *level* or *options* may be non-None. + The *zstd_dict* argument is a :class:`ZstdDict` instance to be used during + compression. + + In binary mode, this function is equivalent to the :class:`ZstdFile` + constructor: ``ZstdFile(file, mode, ...)``. In this case, the + *encoding*, *errors*, and *newline* parameters must not be provided. + + In text mode, a :class:`ZstdFile` object is created, and wrapped in an + :class:`io.TextIOWrapper` instance with the specified encoding, error + handling behavior, and line endings. + + +.. class:: ZstdFile(file, /, mode='rb', *, level=None, options=None, \ + zstd_dict=None) + + Open a Zstandard-compressed file in binary mode. + + A :class:`ZstdFile` can wrap an already-open :term:`file object`, or operate + directly on a named file. The *file* argument specifies either the file + object to wrap, or the name of the file to open (as a :class:`str`, + :class:`bytes` or :term:`path-like <path-like object>` object). If + wrapping an existing file object, the wrapped file will not be closed when + the :class:`ZstdFile` is closed. + + The *mode* argument can be either ``'rb'`` for reading (default), ``'wb'`` + for overwriting, ``'xb'`` for exclusive creation, or ``'ab'`` for appending. + These can equivalently be given as ``'r'``, ``'w'``, ``'x'`` and ``'a'`` + respectively. + + If *file* is a file object (rather than an actual file name), a mode of + ``'w'`` does not truncate the file, and is instead equivalent to ``'a'``. + + When reading, the *options* argument can be a dictionary + providing advanced decompression parameters; see + :class:`DecompressionParameter` for detailed information about supported + parameters. The *zstd_dict* argument is a :class:`ZstdDict` instance to be + used during decompression. When reading, if the *level* + argument is not None, a :exc:`!TypeError` will be raised. + + When writing, the *options* argument can be a dictionary + providing advanced decompression parameters; see + :class:`CompressionParameter` for detailed information about supported + parameters. The *level* argument is the compression level to use when + writing compressed data. Only one of *level* or *options* may be passed. The + *zstd_dict* argument is a :class:`ZstdDict` instance to be used during + compression. + + :class:`!ZstdFile` supports all the members specified by + :class:`io.BufferedIOBase`, except for :meth:`~io.BufferedIOBase.detach` + and :meth:`~io.IOBase.truncate`. + Iteration and the :keyword:`with` statement are supported. + + The following method and attributes are also provided: + + .. method:: peek(size=-1) + + Return buffered data without advancing the file position. At least one + byte of data will be returned, unless EOF has been reached. The exact + number of bytes returned is unspecified (the *size* argument is ignored). + + .. note:: While calling :meth:`peek` does not change the file position of + the :class:`ZstdFile`, it may change the position of the underlying + file object (for example, if the :class:`ZstdFile` was constructed by + passing a file object for *file*). + + .. attribute:: mode + + ``'rb'`` for reading and ``'wb'`` for writing. + + .. attribute:: name + + The name of the Zstandard file. Equivalent to the :attr:`~io.FileIO.name` + attribute of the underlying :term:`file object`. + + +Compressing and decompressing data in memory +-------------------------------------------- + +.. function:: compress(data, level=None, options=None, zstd_dict=None) + + Compress *data* (a :term:`bytes-like object`), returning the compressed + data as a :class:`bytes` object. + + The *level* argument is an integer controlling the level of + compression. *level* is an alternative to setting + :attr:`CompressionParameter.compression_level` in *options*. Use + :meth:`~CompressionParameter.bounds` on + :attr:`~CompressionParameter.compression_level` to get the values that can + be passed for *level*. If advanced compression options are needed, the + *level* argument must be omitted and in the *options* dictionary the + :attr:`!CompressionParameter.compression_level` parameter should be set. + + The *options* argument is a Python dictionary containing advanced + compression parameters. The valid keys and values for compression parameters + are documented as part of the :class:`CompressionParameter` documentation. + + The *zstd_dict* argument is an instance of :class:`ZstdDict` + containing trained data to improve compression efficiency. The + function :func:`train_dict` can be used to generate a Zstandard dictionary. + + +.. function:: decompress(data, zstd_dict=None, options=None) + + Decompress *data* (a :term:`bytes-like object`), returning the uncompressed + data as a :class:`bytes` object. + + The *options* argument is a Python dictionary containing advanced + decompression parameters. The valid keys and values for compression + parameters are documented as part of the :class:`DecompressionParameter` + documentation. + + The *zstd_dict* argument is an instance of :class:`ZstdDict` + containing trained data used during compression. This must be + the same Zstandard dictionary used during compression. + + If *data* is the concatenation of multiple distinct compressed frames, + decompress all of these frames, and return the concatenation of the results. + + +.. class:: ZstdCompressor(level=None, options=None, zstd_dict=None) + + Create a compressor object, which can be used to compress data + incrementally. + + For a more convenient way of compressing a single chunk of data, see the + module-level function :func:`compress`. + + The *level* argument is an integer controlling the level of + compression. *level* is an alternative to setting + :attr:`CompressionParameter.compression_level` in *options*. Use + :meth:`~CompressionParameter.bounds` on + :attr:`~CompressionParameter.compression_level` to get the values that can + be passed for *level*. If advanced compression options are needed, the + *level* argument must be omitted and in the *options* dictionary the + :attr:`!CompressionParameter.compression_level` parameter should be set. + + The *options* argument is a Python dictionary containing advanced + compression parameters. The valid keys and values for compression parameters + are documented as part of the :class:`CompressionParameter` documentation. + + The *zstd_dict* argument is an optional instance of :class:`ZstdDict` + containing trained data to improve compression efficiency. The + function :func:`train_dict` can be used to generate a Zstandard dictionary. + + + .. method:: compress(data, mode=ZstdCompressor.CONTINUE) + + Compress *data* (a :term:`bytes-like object`), returning a :class:`bytes` + object with compressed data if possible, or otherwise an empty + :class:`!bytes` object. Some of *data* may be buffered internally, for + use in later calls to :meth:`!compress` and :meth:`~.flush`. The returned + data should be concatenated with the output of any previous calls to + :meth:`~.compress`. + + The *mode* argument is a :class:`ZstdCompressor` attribute, either + :attr:`~.CONTINUE`, :attr:`~.FLUSH_BLOCK`, + or :attr:`~.FLUSH_FRAME`. + + When all data has been provided to the compressor, call the + :meth:`~.flush` method to finish the compression process. If + :meth:`~.compress` is called with *mode* set to :attr:`~.FLUSH_FRAME`, + :meth:`~.flush` should not be called, as it would write out a new empty + frame. + + .. method:: flush(mode=ZstdCompressor.FLUSH_FRAME) + + Finish the compression process, returning a :class:`bytes` object + containing any data stored in the compressor's internal buffers. + + The *mode* argument is a :class:`ZstdCompressor` attribute, either + :attr:`~.FLUSH_BLOCK`, or :attr:`~.FLUSH_FRAME`. + + .. attribute:: CONTINUE + + Collect more data for compression, which may or may not generate output + immediately. This mode optimizes the compression ratio by maximizing the + amount of data per block and frame. + + .. attribute:: FLUSH_BLOCK + + Complete and write a block to the data stream. The data returned so far + can be immediately decompressed. Past data can still be referenced in + future blocks generated by calls to :meth:`~.compress`, + improving compression. + + .. attribute:: FLUSH_FRAME + + Complete and write out a frame. Future data provided to + :meth:`~.compress` will be written into a new frame and + *cannot* reference past data. + + +.. class:: ZstdDecompressor(zstd_dict=None, options=None) + + Create a decompressor object, which can be used to decompress data + incrementally. + + For a more convenient way of decompressing an entire compressed stream at + once, see the module-level function :func:`decompress`. + + The *options* argument is a Python dictionary containing advanced + decompression parameters. The valid keys and values for compression + parameters are documented as part of the :class:`DecompressionParameter` + documentation. + + The *zstd_dict* argument is an instance of :class:`ZstdDict` + containing trained data used during compression. This must be + the same Zstandard dictionary used during compression. + + .. note:: + This class does not transparently handle inputs containing multiple + compressed frames, unlike the :func:`decompress` function and + :class:`ZstdFile` class. To decompress a multi-frame input, you should + use :func:`decompress`, :class:`ZstdFile` if working with a + :term:`file object`, or multiple :class:`!ZstdDecompressor` instances. + + .. method:: decompress(data, max_length=-1) + + Decompress *data* (a :term:`bytes-like object`), returning + uncompressed data as bytes. Some of *data* may be buffered + internally, for use in later calls to :meth:`!decompress`. + The returned data should be concatenated with the output of any previous + calls to :meth:`!decompress`. + + If *max_length* is non-negative, the method returns at most *max_length* + bytes of decompressed data. If this limit is reached and further + output can be produced, the :attr:`~.needs_input` attribute will + be set to ``False``. In this case, the next call to + :meth:`~.decompress` may provide *data* as ``b''`` to obtain + more of the output. + + If all of the input data was decompressed and returned (either + because this was less than *max_length* bytes, or because + *max_length* was negative), the :attr:`~.needs_input` attribute + will be set to ``True``. + + Attempting to decompress data after the end of a frame will raise a + :exc:`ZstdError`. Any data found after the end of the frame is ignored + and saved in the :attr:`~.unused_data` attribute. + + .. attribute:: eof + + ``True`` if the end-of-stream marker has been reached. + + .. attribute:: unused_data + + Data found after the end of the compressed stream. + + Before the end of the stream is reached, this will be ``b''``. + + .. attribute:: needs_input + + ``False`` if the :meth:`.decompress` method can provide more + decompressed data before requiring new compressed input. + + +Zstandard dictionaries +---------------------- + + +.. function:: train_dict(samples, dict_size) + + Train a Zstandard dictionary, returning a :class:`ZstdDict` instance. + Zstandard dictionaries enable more efficient compression of smaller sizes + of data, which is traditionally difficult to compress due to less + repetition. If you are compressing multiple similar groups of data (such as + similar files), Zstandard dictionaries can improve compression ratios and + speed significantly. + + The *samples* argument (an iterable of :class:`bytes` objects), is the + population of samples used to train the Zstandard dictionary. + + The *dict_size* argument, an integer, is the maximum size (in bytes) the + Zstandard dictionary should be. The Zstandard documentation suggests an + absolute maximum of no more than 100 KB, but the maximum can often be smaller + depending on the data. Larger dictionaries generally slow down compression, + but improve compression ratios. Smaller dictionaries lead to faster + compression, but reduce the compression ratio. + + +.. function:: finalize_dict(zstd_dict, /, samples, dict_size, level) + + An advanced function for converting a "raw content" Zstandard dictionary into + a regular Zstandard dictionary. "Raw content" dictionaries are a sequence of + bytes that do not need to follow the structure of a normal Zstandard + dictionary. + + The *zstd_dict* argument is a :class:`ZstdDict` instance with + the :attr:`~ZstdDict.dict_content` containing the raw dictionary contents. + + The *samples* argument (an iterable of :class:`bytes` objects), contains + sample data for generating the Zstandard dictionary. + + The *dict_size* argument, an integer, is the maximum size (in bytes) the + Zstandard dictionary should be. See :func:`train_dict` for + suggestions on the maximum dictionary size. + + The *level* argument (an integer) is the compression level expected to be + passed to the compressors using this dictionary. The dictionary information + varies for each compression level, so tuning for the proper compression + level can make compression more efficient. + + +.. class:: ZstdDict(dict_content, /, *, is_raw=False) + + A wrapper around Zstandard dictionaries. Dictionaries can be used to improve + the compression of many small chunks of data. Use :func:`train_dict` if you + need to train a new dictionary from sample data. + + The *dict_content* argument (a :term:`bytes-like object`), is the already + trained dictionary information. + + The *is_raw* argument, a boolean, is an advanced parameter controlling the + meaning of *dict_content*. ``True`` means *dict_content* is a "raw content" + dictionary, without any format restrictions. ``False`` means *dict_content* + is an ordinary Zstandard dictionary, created from Zstandard functions, + for example, :func:`train_dict` or the external :program:`zstd` CLI. + + When passing a :class:`!ZstdDict` to a function, the + :attr:`!as_digested_dict` and :attr:`!as_undigested_dict` attributes can + control how the dictionary is loaded by passing them as the ``zstd_dict`` + argument, for example, ``compress(data, zstd_dict=zd.as_digested_dict)``. + Digesting a dictionary is a costly operation that occurs when loading a + Zstandard dictionary. When making multiple calls to compression or + decompression, passing a digested dictionary will reduce the overhead of + loading the dictionary. + + .. list-table:: Difference for compression + :widths: 10 14 10 + :header-rows: 1 + + * - + - Digested dictionary + - Undigested dictionary + * - Advanced parameters of the compressor which may be overridden by + the dictionary's parameters + - ``window_log``, ``hash_log``, ``chain_log``, ``search_log``, + ``min_match``, ``target_length``, ``strategy``, + ``enable_long_distance_matching``, ``ldm_hash_log``, + ``ldm_min_match``, ``ldm_bucket_size_log``, ``ldm_hash_rate_log``, + and some non-public parameters. + - None + * - :class:`!ZstdDict` internally caches the dictionary + - Yes. It's faster when loading a digested dictionary again with the + same compression level. + - No. If you wish to load an undigested dictionary multiple times, + consider reusing a compressor object. + + If passing a :class:`!ZstdDict` without any attribute, an undigested + dictionary is passed by default when compressing and a digested dictionary + is generated if necessary and passed by default when decompressing. + + .. attribute:: dict_content + + The content of the Zstandard dictionary, a ``bytes`` object. It's the + same as the *dict_content* argument in the ``__init__`` method. It can + be used with other programs, such as the ``zstd`` CLI program. + + .. attribute:: dict_id + + Identifier of the Zstandard dictionary, a non-negative int value. + + Non-zero means the dictionary is ordinary, created by Zstandard + functions and following the Zstandard format. + + ``0`` means a "raw content" dictionary, free of any format restriction, + used for advanced users. + + .. note:: + + The meaning of ``0`` for :attr:`!ZstdDict.dict_id` is different + from the ``dictionary_id`` attribute to the :func:`get_frame_info` + function. + + .. attribute:: as_digested_dict + + Load as a digested dictionary. + + .. attribute:: as_undigested_dict + + Load as an undigested dictionary. + + +Advanced parameter control +-------------------------- + +.. class:: CompressionParameter() + + An :class:`~enum.IntEnum` containing the advanced compression parameter + keys that can be used when compressing data. + + The :meth:`~.bounds` method can be used on any attribute to get the valid + values for that parameter. + + Parameters are optional; any omitted parameter will have it's value selected + automatically. + + Example getting the lower and upper bound of :attr:`~.compression_level`:: + + lower, upper = CompressionParameter.compression_level.bounds() + + Example setting the :attr:`~.window_log` to the maximum size:: + + _lower, upper = CompressionParameter.window_log.bounds() + options = {CompressionParameter.window_log: upper} + compress(b'venezuelan beaver cheese', options=options) + + .. method:: bounds() + + Return the tuple of int bounds, ``(lower, upper)``, of a compression + parameter. This method should be called on the attribute you wish to + retrieve the bounds of. For example, to get the valid values for + :attr:`~.compression_level`, one may check the result of + ``CompressionParameter.compression_level.bounds()``. + + Both the lower and upper bounds are inclusive. + + .. attribute:: compression_level + + A high-level means of setting other compression parameters that affect + the speed and ratio of compressing data. Setting the level to zero uses + :attr:`COMPRESSION_LEVEL_DEFAULT`. + + .. attribute:: window_log + + Maximum allowed back-reference distance the compressor can use when + compressing data, expressed as power of two, ``1 << window_log`` bytes. + This parameter greatly influences the memory usage of compression. Higher + values require more memory but gain better compression values. + + A value of zero causes the value to be selected automatically. + + .. attribute:: hash_log + + Size of the initial probe table, as a power of two. The resulting memory + usage is ``1 << (hash_log+2)`` bytes. Larger tables improve compression + ratio of strategies <= :attr:`~Strategy.dfast`, and improve compression + speed of strategies > :attr:`~Strategy.dfast`. + + A value of zero causes the value to be selected automatically. + + .. attribute:: chain_log + + Size of the multi-probe search table, as a power of two. The resulting + memory usage is ``1 << (chain_log+2)`` bytes. Larger tables result in + better and slower compression. This parameter has no effect for the + :attr:`~Strategy.fast` strategy. It's still useful when using + :attr:`~Strategy.dfast` strategy, in which case it defines a secondary + probe table. + + A value of zero causes the value to be selected automatically. + + .. attribute:: search_log + + Number of search attempts, as a power of two. More attempts result in + better and slower compression. This parameter is useless for + :attr:`~Strategy.fast` and :attr:`~Strategy.dfast` strategies. + + A value of zero causes the value to be selected automatically. + + .. attribute:: min_match + + Minimum size of searched matches. Larger values increase compression and + decompression speed, but decrease ratio. Note that Zstandard can still + find matches of smaller size, it just tweaks its search algorithm to look + for this size and larger. For all strategies < :attr:`~Strategy.btopt`, + the effective minimum is ``4``; for all strategies + > :attr:`~Strategy.fast`, the effective maximum is ``6``. + + A value of zero causes the value to be selected automatically. + + .. attribute:: target_length + + The impact of this field depends on the selected :class:`Strategy`. + + For strategies :attr:`~Strategy.btopt`, :attr:`~Strategy.btultra` and + :attr:`~Strategy.btultra2`, the value is the length of a match + considered "good enough" to stop searching. Larger values make + compression ratios better, but compresses slower. + + For strategy :attr:`~Strategy.fast`, it is the distance between match + sampling. Larger values make compression faster, but with a worse + compression ratio. + + A value of zero causes the value to be selected automatically. + + .. attribute:: strategy + + The higher the value of selected strategy, the more complex the + compression technique used by zstd, resulting in higher compression + ratios but slower compression. + + .. seealso:: :class:`Strategy` + + .. attribute:: enable_long_distance_matching + + Long distance matching can be used to improve compression for large + inputs by finding large matches at greater distances. It increases memory + usage and window size. + + ``True`` or ``1`` enable long distance matching while ``False`` or ``0`` + disable it. + + Enabling this parameter increases default + :attr:`~CompressionParameter.window_log` to 128 MiB except when expressly + set to a different value. This setting is enabled by default if + :attr:`!window_log` >= 128 MiB and the compression + strategy >= :attr:`~Strategy.btopt` (compression level 16+). + + .. attribute:: ldm_hash_log + + Size of the table for long distance matching, as a power of two. Larger + values increase memory usage and compression ratio, but decrease + compression speed. + + A value of zero causes the value to be selected automatically. + + .. attribute:: ldm_min_match + + Minimum match size for long distance matcher. Larger or too small values + can often decrease the compression ratio. + + A value of zero causes the value to be selected automatically. + + .. attribute:: ldm_bucket_size_log + + Log size of each bucket in the long distance matcher hash table for + collision resolution. Larger values improve collision resolution but + decrease compression speed. + + A value of zero causes the value to be selected automatically. + + .. attribute:: ldm_hash_rate_log + + Frequency of inserting/looking up entries into the long distance matcher + hash table. Larger values improve compression speed. Deviating far from + the default value will likely result in a compression ratio decrease. + + A value of zero causes the value to be selected automatically. + + .. attribute:: checksum_flag + + A four-byte checksum using XXHash64 of the uncompressed content is + written at the end of each frame. Zstandard's decompression code verifies + the checksum. If there is a mismatch a :class:`ZstdError` exception is + raised. + + ``True`` or ``1`` enable checksum generation while ``False`` or ``0`` + disable it. + + .. attribute:: dict_id_flag + + When compressing with a :class:`ZstdDict`, the dictionary's ID is written + into the frame header. + + ``True`` or ``1`` enable storing the dictionary ID while ``False`` or + ``0`` disable it. + + .. attribute:: nb_workers + + Select how many threads will be spawned to compress in parallel. When + :attr:`!nb_workers` > 0, enables multi-threaded compression, a value of + ``1`` means "one-thread multi-threaded mode". More workers improve speed, + but also increase memory usage and slightly reduce compression ratio. + + A value of zero disables multi-threading. + + .. attribute:: job_size + + Size of a compression job, in bytes. This value is enforced only when + :attr:`~CompressionParameter.nb_workers` >= 1. Each compression job is + completed in parallel, so this value can indirectly impact the number of + active threads. + + A value of zero causes the value to be selected automatically. + + .. attribute:: overlap_log + + Sets how much data is reloaded from previous jobs (threads) for new jobs + to be used by the look behind window during compression. This value is + only used when :attr:`~CompressionParameter.nb_workers` >= 1. Acceptable + values vary from 0 to 9. + + * 0 means dynamically set the overlap amount + * 1 means no overlap + * 9 means use a full window size from the previous job + + Each increment halves/doubles the overlap size. "8" means an overlap of + ``window_size/2``, "7" means an overlap of ``window_size/4``, etc. + +.. class:: DecompressionParameter() + + An :class:`~enum.IntEnum` containing the advanced decompression parameter + keys that can be used when decompressing data. Parameters are optional; any + omitted parameter will have it's value selected automatically. + + The :meth:`~.bounds` method can be used on any attribute to get the valid + values for that parameter. + + Example setting the :attr:`~.window_log_max` to the maximum size:: + + data = compress(b'Some very long buffer of bytes...') + + _lower, upper = DecompressionParameter.window_log_max.bounds() + + options = {DecompressionParameter.window_log_max: upper} + decompress(data, options=options) + + .. method:: bounds() + + Return the tuple of int bounds, ``(lower, upper)``, of a decompression + parameter. This method should be called on the attribute you wish to + retrieve the bounds of. + + Both the lower and upper bounds are inclusive. + + .. attribute:: window_log_max + + The base-two logarithm of the maximum size of the window used during + decompression. This can be useful to limit the amount of memory used when + decompressing data. A larger maximum window size leads to faster + decompression. + + A value of zero causes the value to be selected automatically. + + +.. class:: Strategy() + + An :class:`~enum.IntEnum` containing strategies for compression. + Higher-numbered strategies correspond to more complex and slower + compression. + + .. note:: + + The values of attributes of :class:`!Strategy` are not necessarily stable + across zstd versions. Only the ordering of the attributes may be relied + upon. The attributes are listed below in order. + + The following strategies are available: + + .. attribute:: fast + + .. attribute:: dfast + + .. attribute:: greedy + + .. attribute:: lazy + + .. attribute:: lazy2 + + .. attribute:: btlazy2 + + .. attribute:: btopt + + .. attribute:: btultra + + .. attribute:: btultra2 + + +Miscellaneous +------------- + +.. function:: get_frame_info(frame_buffer) + + Retrieve a :class:`FrameInfo` object containing metadata about a Zstandard + frame. Frames contain metadata related to the compressed data they hold. + + +.. class:: FrameInfo + + Metadata related to a Zstandard frame. + + .. attribute:: decompressed_size + + The size of the decompressed contents of the frame. + + .. attribute:: dictionary_id + + An integer representing the Zstandard dictionary ID needed for + decompressing the frame. ``0`` means the dictionary ID was not + recorded in the frame header. This may mean that a Zstandard dictionary + is not needed, or that the ID of a required dictionary was not recorded. + + +.. attribute:: COMPRESSION_LEVEL_DEFAULT + + The default compression level for Zstandard: ``3``. + + +.. attribute:: zstd_version_info + + Version number of the runtime zstd library as a tuple of integers + (major, minor, release). + + +Examples +-------- + +Reading in a compressed file: + +.. code-block:: python + + from compression import zstd + + with zstd.open("file.zst") as f: + file_content = f.read() + +Creating a compressed file: + +.. code-block:: python + + from compression import zstd + + data = b"Insert Data Here" + with zstd.open("file.zst", "w") as f: + f.write(data) + +Compressing data in memory: + +.. code-block:: python + + from compression import zstd + + data_in = b"Insert Data Here" + data_out = zstd.compress(data_in) + +Incremental compression: + +.. code-block:: python + + from compression import zstd + + comp = zstd.ZstdCompressor() + out1 = comp.compress(b"Some data\n") + out2 = comp.compress(b"Another piece of data\n") + out3 = comp.compress(b"Even more data\n") + out4 = comp.flush() + # Concatenate all the partial results: + result = b"".join([out1, out2, out3, out4]) + +Writing compressed data to an already-open file: + +.. code-block:: python + + from compression import zstd + + with open("myfile", "wb") as f: + f.write(b"This data will not be compressed\n") + with zstd.open(f, "w") as zstf: + zstf.write(b"This *will* be compressed\n") + f.write(b"Not compressed\n") + +Creating a compressed file using compression parameters: + +.. code-block:: python + + from compression import zstd + + options = { + zstd.CompressionParameter.checksum_flag: 1 + } + with zstd.open("file.zst", "w", options=options) as f: + f.write(b"Mind if I squeeze in?") diff --git a/Doc/library/curses.rst b/Doc/library/curses.rst index 137504c51b4..0b13c559295 100644 --- a/Doc/library/curses.rst +++ b/Doc/library/curses.rst @@ -68,7 +68,7 @@ The module :mod:`curses` defines the following exception: The module :mod:`curses` defines the following functions: -.. function:: assume_default_colors(fg, bg) +.. function:: assume_default_colors(fg, bg, /) Allow use of default values for colors on terminals supporting this feature. Use this to support transparency in your application. @@ -988,6 +988,10 @@ the following methods and attributes: window.getstr(y, x, n) Read a bytes object from the user, with primitive line editing capacity. + The maximum value for *n* is 2047. + + .. versionchanged:: 3.14 + The maximum value for *n* was increased from 1023 to 2047. .. method:: window.getyx() @@ -1079,6 +1083,10 @@ the following methods and attributes: current cursor position, or at *y*, *x* if specified. Attributes are stripped from the characters. If *n* is specified, :meth:`instr` returns a string at most *n* characters long (exclusive of the trailing NUL). + The maximum value for *n* is 2047. + + .. versionchanged:: 3.14 + The maximum value for *n* was increased from 1023 to 2047. .. method:: window.is_linetouched(line) diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst index 3470f42a6c6..16ed3215bc2 100644 --- a/Doc/library/datetime.rst +++ b/Doc/library/datetime.rst @@ -1502,11 +1502,11 @@ Instance methods: returned by :func:`time.time`. Naive :class:`.datetime` instances are assumed to represent local - time and this method relies on the platform C :c:func:`mktime` - function to perform the conversion. Since :class:`.datetime` - supports wider range of values than :c:func:`mktime` on many - platforms, this method may raise :exc:`OverflowError` or :exc:`OSError` - for times far in the past or far in the future. + time and this method relies on platform C functions to perform + the conversion. Since :class:`.datetime` supports a wider range of + values than the platform C functions on many platforms, this + method may raise :exc:`OverflowError` or :exc:`OSError` for times + far in the past or far in the future. For aware :class:`.datetime` instances, the return value is computed as:: @@ -1519,6 +1519,10 @@ Instance methods: The :meth:`timestamp` method uses the :attr:`.fold` attribute to disambiguate the times during a repeated interval. + .. versionchanged:: 3.6 + This method no longer relies on the platform C :c:func:`mktime` + function to perform conversions. + .. note:: There is no method to obtain the POSIX timestamp directly from a diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst index f53c1f34670..10ddfa02b43 100644 --- a/Doc/library/decimal.rst +++ b/Doc/library/decimal.rst @@ -2,7 +2,7 @@ ===================================================================== .. module:: decimal - :synopsis: Implementation of the General Decimal Arithmetic Specification. + :synopsis: Implementation of the General Decimal Arithmetic Specification. .. moduleauthor:: Eric Price <eprice at tjhsst.edu> .. moduleauthor:: Facundo Batista <facundo at taniquetil.com.ar> @@ -121,7 +121,7 @@ reset them before monitoring a calculation. .. _decimal-tutorial: -Quick-start Tutorial +Quick-start tutorial -------------------- The usual start to using decimals is importing the module, viewing the current @@ -1096,40 +1096,52 @@ In addition to the three supplied contexts, new contexts can be created with the default values are copied from the :const:`DefaultContext`. If the *flags* field is not specified or is :const:`None`, all flags are cleared. - *prec* is an integer in the range [``1``, :const:`MAX_PREC`] that sets - the precision for arithmetic operations in the context. + .. attribute:: prec - The *rounding* option is one of the constants listed in the section - `Rounding Modes`_. + An integer in the range [``1``, :const:`MAX_PREC`] that sets + the precision for arithmetic operations in the context. - The *traps* and *flags* fields list any signals to be set. Generally, new - contexts should only set traps and leave the flags clear. + .. attribute:: rounding - The *Emin* and *Emax* fields are integers specifying the outer limits allowable - for exponents. *Emin* must be in the range [:const:`MIN_EMIN`, ``0``], - *Emax* in the range [``0``, :const:`MAX_EMAX`]. + One of the constants listed in the section `Rounding Modes`_. - The *capitals* field is either ``0`` or ``1`` (the default). If set to - ``1``, exponents are printed with a capital ``E``; otherwise, a - lowercase ``e`` is used: ``Decimal('6.02e+23')``. + .. attribute:: traps + flags - The *clamp* field is either ``0`` (the default) or ``1``. - If set to ``1``, the exponent ``e`` of a :class:`Decimal` - instance representable in this context is strictly limited to the - range ``Emin - prec + 1 <= e <= Emax - prec + 1``. If *clamp* is - ``0`` then a weaker condition holds: the adjusted exponent of - the :class:`Decimal` instance is at most :attr:`~Context.Emax`. When *clamp* is - ``1``, a large normal number will, where possible, have its - exponent reduced and a corresponding number of zeros added to its - coefficient, in order to fit the exponent constraints; this - preserves the value of the number but loses information about - significant trailing zeros. For example:: + Lists of any signals to be set. Generally, new contexts should only set + traps and leave the flags clear. - >>> Context(prec=6, Emax=999, clamp=1).create_decimal('1.23e999') - Decimal('1.23000E+999') + .. attribute:: Emin + Emax - A *clamp* value of ``1`` allows compatibility with the - fixed-width decimal interchange formats specified in IEEE 754. + Integers specifying the outer limits allowable for exponents. *Emin* must + be in the range [:const:`MIN_EMIN`, ``0``], *Emax* in the range + [``0``, :const:`MAX_EMAX`]. + + .. attribute:: capitals + + Either ``0`` or ``1`` (the default). If set to + ``1``, exponents are printed with a capital ``E``; otherwise, a + lowercase ``e`` is used: ``Decimal('6.02e+23')``. + + .. attribute:: clamp + + Either ``0`` (the default) or ``1``. If set to ``1``, the exponent ``e`` + of a :class:`Decimal` instance representable in this context is strictly + limited to the range ``Emin - prec + 1 <= e <= Emax - prec + 1``. + If *clamp* is ``0`` then a weaker condition holds: the adjusted exponent of + the :class:`Decimal` instance is at most :attr:`~Context.Emax`. When *clamp* is + ``1``, a large normal number will, where possible, have its + exponent reduced and a corresponding number of zeros added to its + coefficient, in order to fit the exponent constraints; this + preserves the value of the number but loses information about + significant trailing zeros. For example:: + + >>> Context(prec=6, Emax=999, clamp=1).create_decimal('1.23e999') + Decimal('1.23000E+999') + + A *clamp* value of ``1`` allows compatibility with the + fixed-width decimal interchange formats specified in IEEE 754. The :class:`Context` class defines several general purpose methods as well as a large number of methods for doing arithmetic directly in a given context. @@ -1769,7 +1781,7 @@ The following table summarizes the hierarchy of signals:: .. _decimal-notes: -Floating-Point Notes +Floating-point notes -------------------- diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst index 7e367a0f2b6..2ecce3dba5a 100644 --- a/Doc/library/functions.rst +++ b/Doc/library/functions.rst @@ -1154,44 +1154,44 @@ are always available. They are listed here in alphabetical order. .. function:: locals() - Return a mapping object representing the current local symbol table, with - variable names as the keys, and their currently bound references as the - values. - - At module scope, as well as when using :func:`exec` or :func:`eval` with - a single namespace, this function returns the same namespace as - :func:`globals`. - - At class scope, it returns the namespace that will be passed to the - metaclass constructor. - - When using ``exec()`` or ``eval()`` with separate local and global - arguments, it returns the local namespace passed in to the function call. - - In all of the above cases, each call to ``locals()`` in a given frame of - execution will return the *same* mapping object. Changes made through - the mapping object returned from ``locals()`` will be visible as assigned, - reassigned, or deleted local variables, and assigning, reassigning, or - deleting local variables will immediately affect the contents of the - returned mapping object. - - In an :term:`optimized scope` (including functions, generators, and - coroutines), each call to ``locals()`` instead returns a fresh dictionary - containing the current bindings of the function's local variables and any - nonlocal cell references. In this case, name binding changes made via the - returned dict are *not* written back to the corresponding local variables - or nonlocal cell references, and assigning, reassigning, or deleting local - variables and nonlocal cell references does *not* affect the contents - of previously returned dictionaries. - - Calling ``locals()`` as part of a comprehension in a function, generator, or - coroutine is equivalent to calling it in the containing scope, except that - the comprehension's initialised iteration variables will be included. In - other scopes, it behaves as if the comprehension were running as a nested - function. - - Calling ``locals()`` as part of a generator expression is equivalent to - calling it in a nested generator function. + Return a mapping object representing the current local symbol table, with + variable names as the keys, and their currently bound references as the + values. + + At module scope, as well as when using :func:`exec` or :func:`eval` with + a single namespace, this function returns the same namespace as + :func:`globals`. + + At class scope, it returns the namespace that will be passed to the + metaclass constructor. + + When using ``exec()`` or ``eval()`` with separate local and global + arguments, it returns the local namespace passed in to the function call. + + In all of the above cases, each call to ``locals()`` in a given frame of + execution will return the *same* mapping object. Changes made through + the mapping object returned from ``locals()`` will be visible as assigned, + reassigned, or deleted local variables, and assigning, reassigning, or + deleting local variables will immediately affect the contents of the + returned mapping object. + + In an :term:`optimized scope` (including functions, generators, and + coroutines), each call to ``locals()`` instead returns a fresh dictionary + containing the current bindings of the function's local variables and any + nonlocal cell references. In this case, name binding changes made via the + returned dict are *not* written back to the corresponding local variables + or nonlocal cell references, and assigning, reassigning, or deleting local + variables and nonlocal cell references does *not* affect the contents + of previously returned dictionaries. + + Calling ``locals()`` as part of a comprehension in a function, generator, or + coroutine is equivalent to calling it in the containing scope, except that + the comprehension's initialised iteration variables will be included. In + other scopes, it behaves as if the comprehension were running as a nested + function. + + Calling ``locals()`` as part of a generator expression is equivalent to + calling it in a nested generator function. .. versionchanged:: 3.12 The behaviour of ``locals()`` in a comprehension has been updated as diff --git a/Doc/library/importlib.resources.abc.rst b/Doc/library/importlib.resources.abc.rst index 7a77466bcba..8253a33f591 100644 --- a/Doc/library/importlib.resources.abc.rst +++ b/Doc/library/importlib.resources.abc.rst @@ -49,44 +49,44 @@ .. method:: open_resource(resource) :abstractmethod: - Returns an opened, :term:`file-like object` for binary reading - of the *resource*. + Returns an opened, :term:`file-like object` for binary reading + of the *resource*. - If the resource cannot be found, :exc:`FileNotFoundError` is - raised. + If the resource cannot be found, :exc:`FileNotFoundError` is + raised. .. method:: resource_path(resource) :abstractmethod: - Returns the file system path to the *resource*. + Returns the file system path to the *resource*. - If the resource does not concretely exist on the file system, - raise :exc:`FileNotFoundError`. + If the resource does not concretely exist on the file system, + raise :exc:`FileNotFoundError`. .. method:: is_resource(name) :abstractmethod: - Returns ``True`` if the named *name* is considered a resource. - :exc:`FileNotFoundError` is raised if *name* does not exist. + Returns ``True`` if the named *name* is considered a resource. + :exc:`FileNotFoundError` is raised if *name* does not exist. .. method:: contents() :abstractmethod: - Returns an :term:`iterable` of strings over the contents of - the package. Do note that it is not required that all names - returned by the iterator be actual resources, e.g. it is - acceptable to return names for which :meth:`is_resource` would - be false. - - Allowing non-resource names to be returned is to allow for - situations where how a package and its resources are stored - are known a priori and the non-resource names would be useful. - For instance, returning subdirectory names is allowed so that - when it is known that the package and resources are stored on - the file system then those subdirectory names can be used - directly. - - The abstract method returns an iterable of no items. + Returns an :term:`iterable` of strings over the contents of + the package. Do note that it is not required that all names + returned by the iterator be actual resources, e.g. it is + acceptable to return names for which :meth:`is_resource` would + be false. + + Allowing non-resource names to be returned is to allow for + situations where how a package and its resources are stored + are known a priori and the non-resource names would be useful. + For instance, returning subdirectory names is allowed so that + when it is known that the package and resources are stored on + the file system then those subdirectory names can be used + directly. + + The abstract method returns an iterable of no items. .. class:: Traversable diff --git a/Doc/library/io.rst b/Doc/library/io.rst index 3aa2f35f05e..de5cab5aee6 100644 --- a/Doc/library/io.rst +++ b/Doc/library/io.rst @@ -528,14 +528,13 @@ I/O Base Classes It inherits from :class:`IOBase`. The main difference with :class:`RawIOBase` is that methods :meth:`read`, - :meth:`readinto` and :meth:`write` will try (respectively) to read as much - input as requested or to consume all given output, at the expense of - making perhaps more than one system call. + :meth:`readinto` and :meth:`write` will try (respectively) to read + as much input as requested or to emit all provided data. - In addition, those methods can raise :exc:`BlockingIOError` if the - underlying raw stream is in non-blocking mode and cannot take or give - enough data; unlike their :class:`RawIOBase` counterparts, they will - never return ``None``. + In addition, if the underlying raw stream is in non-blocking mode, when the + system returns would block :meth:`write` will raise :exc:`BlockingIOError` + with :attr:`BlockingIOError.characters_written` and :meth:`read` will return + data read so far or ``None`` if no data is available. Besides, the :meth:`read` method does not have a default implementation that defers to :meth:`readinto`. @@ -568,29 +567,40 @@ I/O Base Classes .. method:: read(size=-1, /) - Read and return up to *size* bytes. If the argument is omitted, ``None``, - or negative, data is read and returned until EOF is reached. An empty - :class:`bytes` object is returned if the stream is already at EOF. + Read and return up to *size* bytes. If the argument is omitted, ``None``, + or negative read as much as possible. - If the argument is positive, and the underlying raw stream is not - interactive, multiple raw reads may be issued to satisfy the byte count - (unless EOF is reached first). But for interactive raw streams, at most - one raw read will be issued, and a short result does not imply that EOF is - imminent. + Fewer bytes may be returned than requested. An empty :class:`bytes` object + is returned if the stream is already at EOF. More than one read may be + made and calls may be retried if specific errors are encountered, see + :meth:`os.read` and :pep:`475` for more details. Less than size bytes + being returned does not imply that EOF is imminent. - A :exc:`BlockingIOError` is raised if the underlying raw stream is in - non blocking-mode, and has no data available at the moment. + When reading as much as possible the default implementation will use + ``raw.readall`` if available (which should implement + :meth:`RawIOBase.readall`), otherwise will read in a loop until read + returns ``None``, an empty :class:`bytes`, or a non-retryable error. For + most streams this is to EOF, but for non-blocking streams more data may + become available. + + .. note:: + + When the underlying raw stream is non-blocking, implementations may + either raise :exc:`BlockingIOError` or return ``None`` if no data is + available. :mod:`io` implementations return ``None``. .. method:: read1(size=-1, /) - Read and return up to *size* bytes, with at most one call to the - underlying raw stream's :meth:`~RawIOBase.read` (or - :meth:`~RawIOBase.readinto`) method. This can be useful if you are - implementing your own buffering on top of a :class:`BufferedIOBase` - object. + Read and return up to *size* bytes, calling :meth:`~RawIOBase.readinto` + which may retry if :py:const:`~errno.EINTR` is encountered per + :pep:`475`. If *size* is ``-1`` or not provided, the implementation will + choose an arbitrary value for *size*. - If *size* is ``-1`` (the default), an arbitrary number of bytes are - returned (more than zero unless EOF is reached). + .. note:: + + When the underlying raw stream is non-blocking, implementations may + either raise :exc:`BlockingIOError` or return ``None`` if no data is + available. :mod:`io` implementations return ``None``. .. method:: readinto(b, /) @@ -767,34 +777,21 @@ than raw I/O does. .. method:: peek(size=0, /) - Return bytes from the stream without advancing the position. At most one - single read on the raw stream is done to satisfy the call. The number of - bytes returned may be less or more than requested. + Return bytes from the stream without advancing the position. The number of + bytes returned may be less or more than requested. If the underlying raw + stream is non-blocking and the operation would block, returns empty bytes. .. method:: read(size=-1, /) - Read and return *size* bytes, or if *size* is not given or negative, until - EOF or if the read call would block in non-blocking mode. - - .. note:: - - When the underlying raw stream is non-blocking, a :exc:`BlockingIOError` - may be raised if a read operation cannot be completed immediately. + In :class:`BufferedReader` this is the same as :meth:`io.BufferedIOBase.read` .. method:: read1(size=-1, /) - Read and return up to *size* bytes with only one call on the raw stream. - If at least one byte is buffered, only buffered bytes are returned. - Otherwise, one raw stream read call is made. + In :class:`BufferedReader` this is the same as :meth:`io.BufferedIOBase.read1` .. versionchanged:: 3.7 The *size* argument is now optional. - .. note:: - - When the underlying raw stream is non-blocking, a :exc:`BlockingIOError` - may be raised if a read operation cannot be completed immediately. - .. class:: BufferedWriter(raw, buffer_size=DEFAULT_BUFFER_SIZE) A buffered binary stream providing higher-level access to a writeable, non @@ -826,8 +823,8 @@ than raw I/O does. Write the :term:`bytes-like object`, *b*, and return the number of bytes written. When in non-blocking mode, a - :exc:`BlockingIOError` is raised if the buffer needs to be written out but - the raw stream blocks. + :exc:`BlockingIOError` with :attr:`BlockingIOError.characters_written` set + is raised if the buffer needs to be written out but the raw stream blocks. .. class:: BufferedRandom(raw, buffer_size=DEFAULT_BUFFER_SIZE) @@ -894,9 +891,10 @@ Text I/O .. attribute:: buffer - The underlying binary buffer (a :class:`BufferedIOBase` instance) that - :class:`TextIOBase` deals with. This is not part of the - :class:`TextIOBase` API and may not exist in some implementations. + The underlying binary buffer (a :class:`BufferedIOBase` + or :class:`RawIOBase` instance) that :class:`TextIOBase` deals with. + This is not part of the :class:`TextIOBase` API and may not exist + in some implementations. .. method:: detach() diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst index 6c43d5fe166..80e33c4a1df 100644 --- a/Doc/library/multiprocessing.rst +++ b/Doc/library/multiprocessing.rst @@ -1369,6 +1369,12 @@ object -- see :ref:`multiprocessing-managers`. A solitary difference from its close analog exists: its ``acquire`` method's first argument is named *block*, as is consistent with :meth:`Lock.acquire`. + .. method:: locked() + + Return a boolean indicating whether this object is locked right now. + + .. versionadded:: 3.14 + .. note:: On macOS, this is indistinguishable from :class:`Semaphore` because ``sem_getvalue()`` is not implemented on that platform. @@ -1521,6 +1527,12 @@ object -- see :ref:`multiprocessing-managers`. A solitary difference from its close analog exists: its ``acquire`` method's first argument is named *block*, as is consistent with :meth:`Lock.acquire`. + .. method:: locked() + + Return a boolean indicating whether this object is locked right now. + + .. versionadded:: 3.14 + .. note:: On macOS, ``sem_timedwait`` is unsupported, so calling ``acquire()`` with diff --git a/Doc/library/pdb.rst b/Doc/library/pdb.rst index a0304edddf6..f4b51664545 100644 --- a/Doc/library/pdb.rst +++ b/Doc/library/pdb.rst @@ -80,7 +80,7 @@ The debugger's prompt is ``(Pdb)``, which is the indicator that you are in debug You can also invoke :mod:`pdb` from the command line to debug other scripts. For example:: - python -m pdb [-c command] (-m module | pyfile) [args ...] + python -m pdb [-c command] (-m module | -p pid | pyfile) [args ...] When invoked as a module, pdb will automatically enter post-mortem debugging if the program being debugged exits abnormally. After post-mortem debugging (or @@ -104,6 +104,24 @@ useful than quitting the debugger upon program's exit. .. versionchanged:: 3.7 Added the ``-m`` option. +.. option:: -p, --pid <pid> + + Attach to the process with the specified PID. + + .. versionadded:: 3.14 + + +To attach to a running Python process for remote debugging, use the ``-p`` or +``--pid`` option with the target process's PID:: + + python -m pdb -p 1234 + +.. note:: + + Attaching to a process that is blocked in a system call or waiting for I/O + will only work once the next bytecode instruction is executed or when the + process receives a signal. + Typical usage to execute a statement under control of the debugger is:: >>> import pdb diff --git a/Doc/library/re.rst b/Doc/library/re.rst index eb3b1e5549c..75ebbf11c8e 100644 --- a/Doc/library/re.rst +++ b/Doc/library/re.rst @@ -991,8 +991,8 @@ Functions That way, separator components are always found at the same relative indices within the result list. - Empty matches for the pattern split the string only when not adjacent - to a previous empty match. + Adjacent empty matches are not possible, but an empty match can occur + immediately after a non-empty match. .. code:: pycon @@ -1095,9 +1095,12 @@ Functions The optional argument *count* is the maximum number of pattern occurrences to be replaced; *count* must be a non-negative integer. If omitted or zero, all - occurrences will be replaced. Empty matches for the pattern are replaced only - when not adjacent to a previous empty match, so ``sub('x*', '-', 'abxd')`` returns - ``'-a-b--d-'``. + occurrences will be replaced. + + Adjacent empty matches are not possible, but an empty match can occur + immediately after a non-empty match. + As a result, ``sub('x*', '-', 'abxd')`` returns ``'-a-b--d-'`` + instead of ``'-a-b-d-'``. .. index:: single: \g; in regular expressions @@ -1128,8 +1131,7 @@ Functions .. versionchanged:: 3.7 Unknown escapes in *repl* consisting of ``'\'`` and an ASCII letter now are errors. - Empty matches for the pattern are replaced when adjacent to a previous - non-empty match. + An empty match can occur immediately after a non-empty match. .. versionchanged:: 3.12 Group *id* can only contain ASCII digits. diff --git a/Doc/library/signal.rst b/Doc/library/signal.rst index c28841dbb8c..b0307d3dea1 100644 --- a/Doc/library/signal.rst +++ b/Doc/library/signal.rst @@ -211,8 +211,8 @@ The variables defined in the :mod:`signal` module are: .. data:: SIGSTKFLT - Stack fault on coprocessor. The Linux kernel does not raise this signal: it - can only be raised in user space. + Stack fault on coprocessor. The Linux kernel does not raise this signal: it + can only be raised in user space. .. availability:: Linux. diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst index 8fd5187e3a4..75fd637045d 100644 --- a/Doc/library/socket.rst +++ b/Doc/library/socket.rst @@ -362,10 +362,10 @@ Exceptions Constants ^^^^^^^^^ - The AF_* and SOCK_* constants are now :class:`AddressFamily` and - :class:`SocketKind` :class:`.IntEnum` collections. +The AF_* and SOCK_* constants are now :class:`AddressFamily` and +:class:`SocketKind` :class:`.IntEnum` collections. - .. versionadded:: 3.4 +.. versionadded:: 3.4 .. data:: AF_UNIX AF_INET @@ -773,9 +773,9 @@ Constants Constant to optimize CPU locality, to be used in conjunction with :data:`SO_REUSEPORT`. - .. versionadded:: 3.11 + .. versionadded:: 3.11 - .. availability:: Linux >= 3.9 + .. availability:: Linux >= 3.9 .. data:: SO_REUSEPORT_LB diff --git a/Doc/library/socketserver.rst b/Doc/library/socketserver.rst index 59cfa136a3b..753f12460b8 100644 --- a/Doc/library/socketserver.rst +++ b/Doc/library/socketserver.rst @@ -24,6 +24,8 @@ There are four basic concrete server classes: :meth:`~BaseServer.server_activate`. The other parameters are passed to the :class:`BaseServer` base class. + .. versionchanged:: next + The default queue size is now ``socket.SOMAXCONN`` for :class:`socketserver.TCPServer`. .. class:: UDPServer(server_address, RequestHandlerClass, bind_and_activate=True) |