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|
:mod:`sys` -- system specific functions
=======================================
.. module:: sys
:synopsis: system specific functions
|see_cpython_module| :mod:`python:sys`.
Functions
---------
.. function:: exit(retval=0, /)
Terminate current program with a given exit code. Underlyingly, this
function raises a `SystemExit` exception. If an argument is given, its
value given as an argument to `SystemExit`.
On embedded ports (i.e. all ports but Windows and Unix), an unhandled
`SystemExit` currently causes a :ref:`soft_reset` of MicroPython.
.. function:: atexit(func)
Register *func* to be called upon termination. *func* must be a callable
that takes no arguments, or ``None`` to disable the call. The ``atexit``
function will return the previous value set by this function, which is
initially ``None``.
.. admonition:: Difference to CPython
:class: attention
This function is a MicroPython extension intended to provide similar
functionality to the :mod:`atexit` module in CPython.
.. function:: print_exception(exc, file=sys.stdout, /)
Print exception with a traceback to a file-like object *file* (or
`sys.stdout` by default).
.. admonition:: Difference to CPython
:class: attention
This is simplified version of a function which appears in the
``traceback`` module in CPython. Unlike ``traceback.print_exception()``,
this function takes just exception value instead of exception type,
exception value, and traceback object; *file* argument should be
positional; further arguments are not supported. CPython-compatible
``traceback`` module can be found in `micropython-lib`.
.. function:: settrace(tracefunc)
Enable tracing of bytecode execution. For details see the `CPython
documentation <https://docs.python.org/3/library/sys.html#sys.settrace>`_.
This function requires a custom MicroPython build as it is typically not
present in pre-built firmware (due to it affecting performance). The relevant
configuration option is *MICROPY_PY_SYS_SETTRACE*.
Constants
---------
.. data:: argv
A mutable list of arguments the current program was started with.
.. data:: byteorder
The byte order of the system (``"little"`` or ``"big"``).
.. data:: implementation
Object with information about the current Python implementation. For
MicroPython, it has following attributes:
* *name* - string "micropython"
* *version* - tuple (major, minor, micro, releaselevel), e.g. (1, 22, 0, '')
* *_machine* - string describing the underlying machine
* *_mpy* - supported mpy file-format version (optional attribute)
* *_build* - string that can help identify the configuration that
MicroPython was built with
This object is the recommended way to distinguish MicroPython from other
Python implementations (note that it still may not exist in the very
minimal ports).
Starting with version 1.22.0-preview, the fourth node *releaselevel* in
*implementation.version* is either an empty string or ``"preview"``.
The *_build* entry was added in version 1.25.0 and is a hyphen-separated
set of elements. New elements may be appended in the future so it's best to
access this field using ``sys.implementation._build.split("-")``. The
elements that are currently used are:
* On the unix, webassembly and windows ports the first element is the variant
name, for example ``'standard'``.
* On microcontroller targets, the first element is the board name and the second
element (if present) is the board variant, for example ``'RPI_PICO2-RISCV'``
.. admonition:: Difference to CPython
:class: attention
CPython mandates more attributes for this object, but the actual useful
bare minimum is implemented in MicroPython.
.. data:: maxsize
Maximum value which a native integer type can hold on the current platform,
or maximum value representable by MicroPython integer type, if it's smaller
than platform max value (that is the case for MicroPython ports without
long int support).
This attribute is useful for detecting "bitness" of a platform (32-bit vs
64-bit, etc.). It's recommended to not compare this attribute to some
value directly, but instead count number of bits in it::
bits = 0
v = sys.maxsize
while v:
bits += 1
v >>= 1
if bits > 32:
# 64-bit (or more) platform
...
else:
# 32-bit (or less) platform
# Note that on 32-bit platform, value of bits may be less than 32
# (e.g. 31) due to peculiarities described above, so use "> 16",
# "> 32", "> 64" style of comparisons.
.. data:: modules
Dictionary of loaded modules. On some ports, it may not include builtin
modules.
.. data:: path
A mutable list of directories to search for imported modules.
.. admonition:: Difference to CPython
:class: attention
On MicroPython, an entry with the value ``".frozen"`` will indicate that import
should search :term:`frozen modules <frozen module>` at that point in the search.
If no frozen module is found then search will *not* look for a directory called
``.frozen``, instead it will continue with the next entry in ``sys.path``.
.. data:: platform
The platform that MicroPython is running on. For OS/RTOS ports, this is
usually an identifier of the OS, e.g. ``"linux"``. For baremetal ports it
is an identifier of a board, e.g. ``"pyboard"`` for the original MicroPython
reference board. It thus can be used to distinguish one board from another.
If you need to check whether your program runs on MicroPython (vs other
Python implementation), use `sys.implementation` instead.
.. data:: ps1
ps2
Mutable attributes holding strings, which are used for the REPL prompt. The defaults
give the standard Python prompt of ``>>>`` and ``...``.
.. data:: stderr
Standard error `stream`.
.. data:: stdin
Standard input `stream`.
.. data:: stdout
Standard output `stream`.
.. data:: tracebacklimit
A mutable attribute holding an integer value which is the maximum number of traceback
entries to store in an exception. Set to 0 to disable adding tracebacks. Defaults
to 1000.
Note: this is not available on all ports.
.. data:: version
Python language version that this implementation conforms to, as a string.
.. data:: version_info
Python language version that this implementation conforms to, as a tuple of ints.
.. admonition:: Difference to CPython
:class: attention
Only the first three version numbers (major, minor, micro) are supported and
they can be referenced only by index, not by name.
|
