mirror of
https://github.com/python/cpython.git
synced 2025-10-31 13:41:24 +00:00
4b9aad4999
Enhance the documentation of the Python startup, filesystem encoding and error handling, locale encoding. Add a new "Python UTF-8 Mode" section. * Add "locale encoding" and "filesystem encoding and error handler" to the glossary * Remove documentation from Include/cpython/initconfig.h: move it to Doc/c-api/init_config.rst. * Doc/c-api/init_config.rst: * Document command line options and environment variables * Document default values. * Add a new "Python UTF-8 Mode" section in Doc/library/os.rst. * Add warnings to Py_DecodeLocale() and Py_EncodeLocale() docs. * Document how Python selects the filesystem encoding and error handler at a single place: PyConfig.filesystem_encoding and PyConfig.filesystem_errors. * PyConfig: move orig_argv member at the right place.
427 lines
16 KiB
ReStructuredText
427 lines
16 KiB
ReStructuredText
.. highlight:: c
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.. _os:
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Operating System Utilities
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==========================
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.. c:function:: PyObject* PyOS_FSPath(PyObject *path)
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Return the file system representation for *path*. If the object is a
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:class:`str` or :class:`bytes` object, then its reference count is
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incremented. If the object implements the :class:`os.PathLike` interface,
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then :meth:`~os.PathLike.__fspath__` is returned as long as it is a
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:class:`str` or :class:`bytes` object. Otherwise :exc:`TypeError` is raised
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and ``NULL`` is returned.
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.. versionadded:: 3.6
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.. c:function:: int Py_FdIsInteractive(FILE *fp, const char *filename)
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Return true (nonzero) if the standard I/O file *fp* with name *filename* is
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deemed interactive. This is the case for files for which ``isatty(fileno(fp))``
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is true. If the global flag :c:data:`Py_InteractiveFlag` is true, this function
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also returns true if the *filename* pointer is ``NULL`` or if the name is equal to
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one of the strings ``'<stdin>'`` or ``'???'``.
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.. c:function:: void PyOS_BeforeFork()
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Function to prepare some internal state before a process fork. This
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should be called before calling :c:func:`fork` or any similar function
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that clones the current process.
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Only available on systems where :c:func:`fork` is defined.
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.. warning::
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The C :c:func:`fork` call should only be made from the
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:ref:`"main" thread <fork-and-threads>` (of the
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:ref:`"main" interpreter <sub-interpreter-support>`). The same is
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true for ``PyOS_BeforeFork()``.
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.. versionadded:: 3.7
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.. c:function:: void PyOS_AfterFork_Parent()
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Function to update some internal state after a process fork. This
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should be called from the parent process after calling :c:func:`fork`
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or any similar function that clones the current process, regardless
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of whether process cloning was successful.
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Only available on systems where :c:func:`fork` is defined.
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.. warning::
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The C :c:func:`fork` call should only be made from the
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:ref:`"main" thread <fork-and-threads>` (of the
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:ref:`"main" interpreter <sub-interpreter-support>`). The same is
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true for ``PyOS_AfterFork_Parent()``.
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.. versionadded:: 3.7
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.. c:function:: void PyOS_AfterFork_Child()
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Function to update internal interpreter state after a process fork.
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This must be called from the child process after calling :c:func:`fork`,
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or any similar function that clones the current process, if there is
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any chance the process will call back into the Python interpreter.
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Only available on systems where :c:func:`fork` is defined.
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.. warning::
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The C :c:func:`fork` call should only be made from the
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:ref:`"main" thread <fork-and-threads>` (of the
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:ref:`"main" interpreter <sub-interpreter-support>`). The same is
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true for ``PyOS_AfterFork_Child()``.
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.. versionadded:: 3.7
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.. seealso::
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:func:`os.register_at_fork` allows registering custom Python functions
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to be called by :c:func:`PyOS_BeforeFork()`,
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:c:func:`PyOS_AfterFork_Parent` and :c:func:`PyOS_AfterFork_Child`.
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.. c:function:: void PyOS_AfterFork()
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Function to update some internal state after a process fork; this should be
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called in the new process if the Python interpreter will continue to be used.
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If a new executable is loaded into the new process, this function does not need
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to be called.
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.. deprecated:: 3.7
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This function is superseded by :c:func:`PyOS_AfterFork_Child()`.
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.. c:function:: int PyOS_CheckStack()
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Return true when the interpreter runs out of stack space. This is a reliable
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check, but is only available when :const:`USE_STACKCHECK` is defined (currently
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on Windows using the Microsoft Visual C++ compiler). :const:`USE_STACKCHECK`
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will be defined automatically; you should never change the definition in your
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own code.
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.. c:function:: PyOS_sighandler_t PyOS_getsig(int i)
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Return the current signal handler for signal *i*. This is a thin wrapper around
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either :c:func:`sigaction` or :c:func:`signal`. Do not call those functions
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directly! :c:type:`PyOS_sighandler_t` is a typedef alias for :c:type:`void
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(\*)(int)`.
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.. c:function:: PyOS_sighandler_t PyOS_setsig(int i, PyOS_sighandler_t h)
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Set the signal handler for signal *i* to be *h*; return the old signal handler.
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This is a thin wrapper around either :c:func:`sigaction` or :c:func:`signal`. Do
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not call those functions directly! :c:type:`PyOS_sighandler_t` is a typedef
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alias for :c:type:`void (\*)(int)`.
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.. c:function:: wchar_t* Py_DecodeLocale(const char* arg, size_t *size)
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.. warning::
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This function should not be called directly: use the :c:type:`PyConfig`
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API with the :c:func:`PyConfig_SetBytesString` function which ensures
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that :ref:`Python is preinitialized <c-preinit>`.
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This function must not be called before :ref:`Python is preinitialized
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<c-preinit>` and so that the LC_CTYPE locale is properly configured: see
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the :c:func:`Py_PreInitialize` function.
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Decode a byte string from the :term:`filesystem encoding and error handler`.
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If the error handler is :ref:`surrogateescape error handler
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<surrogateescape>`, undecodable bytes are decoded as characters in range
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U+DC80..U+DCFF; and if a byte sequence can be decoded as a surrogate
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character, the bytes are escaped using the surrogateescape error handler
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instead of decoding them.
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Return a pointer to a newly allocated wide character string, use
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:c:func:`PyMem_RawFree` to free the memory. If size is not ``NULL``, write
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the number of wide characters excluding the null character into ``*size``
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Return ``NULL`` on decoding error or memory allocation error. If *size* is
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not ``NULL``, ``*size`` is set to ``(size_t)-1`` on memory error or set to
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``(size_t)-2`` on decoding error.
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The :term:`filesystem encoding and error handler` are selected by
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:c:func:`PyConfig_Read`: see :c:member:`~PyConfig.filesystem_encoding` and
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:c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
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Decoding errors should never happen, unless there is a bug in the C
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library.
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Use the :c:func:`Py_EncodeLocale` function to encode the character string
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back to a byte string.
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.. seealso::
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The :c:func:`PyUnicode_DecodeFSDefaultAndSize` and
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:c:func:`PyUnicode_DecodeLocaleAndSize` functions.
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.. versionadded:: 3.5
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.. versionchanged:: 3.7
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The function now uses the UTF-8 encoding in the :ref:`Python UTF-8 Mode
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<utf8-mode>`.
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.. versionchanged:: 3.8
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The function now uses the UTF-8 encoding on Windows if
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:c:data:`Py_LegacyWindowsFSEncodingFlag` is zero;
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.. c:function:: char* Py_EncodeLocale(const wchar_t *text, size_t *error_pos)
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Encode a wide character string to the :term:`filesystem encoding and error
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handler`. If the error handler is :ref:`surrogateescape error handler
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<surrogateescape>`, surrogate characters in the range U+DC80..U+DCFF are
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converted to bytes 0x80..0xFF.
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Return a pointer to a newly allocated byte string, use :c:func:`PyMem_Free`
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to free the memory. Return ``NULL`` on encoding error or memory allocation
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error
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If error_pos is not ``NULL``, ``*error_pos`` is set to ``(size_t)-1`` on
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success, or set to the index of the invalid character on encoding error.
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The :term:`filesystem encoding and error handler` are selected by
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:c:func:`PyConfig_Read`: see :c:member:`~PyConfig.filesystem_encoding` and
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:c:member:`~PyConfig.filesystem_errors` members of :c:type:`PyConfig`.
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Use the :c:func:`Py_DecodeLocale` function to decode the bytes string back
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to a wide character string.
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.. warning::
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This function must not be called before :ref:`Python is preinitialized
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<c-preinit>` and so that the LC_CTYPE locale is properly configured: see
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the :c:func:`Py_PreInitialize` function.
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.. seealso::
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The :c:func:`PyUnicode_EncodeFSDefault` and
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:c:func:`PyUnicode_EncodeLocale` functions.
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.. versionadded:: 3.5
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.. versionchanged:: 3.7
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The function now uses the UTF-8 encoding in the :ref:`Python UTF-8 Mode
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<utf8-mode>`.
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.. versionchanged:: 3.8
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The function now uses the UTF-8 encoding on Windows if
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:c:data:`Py_LegacyWindowsFSEncodingFlag` is zero;
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.. _systemfunctions:
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System Functions
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================
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These are utility functions that make functionality from the :mod:`sys` module
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accessible to C code. They all work with the current interpreter thread's
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:mod:`sys` module's dict, which is contained in the internal thread state structure.
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.. c:function:: PyObject *PySys_GetObject(const char *name)
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Return the object *name* from the :mod:`sys` module or ``NULL`` if it does
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not exist, without setting an exception.
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.. c:function:: int PySys_SetObject(const char *name, PyObject *v)
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Set *name* in the :mod:`sys` module to *v* unless *v* is ``NULL``, in which
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case *name* is deleted from the sys module. Returns ``0`` on success, ``-1``
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on error.
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.. c:function:: void PySys_ResetWarnOptions()
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Reset :data:`sys.warnoptions` to an empty list. This function may be
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called prior to :c:func:`Py_Initialize`.
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.. c:function:: void PySys_AddWarnOption(const wchar_t *s)
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Append *s* to :data:`sys.warnoptions`. This function must be called prior
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to :c:func:`Py_Initialize` in order to affect the warnings filter list.
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.. c:function:: void PySys_AddWarnOptionUnicode(PyObject *unicode)
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Append *unicode* to :data:`sys.warnoptions`.
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Note: this function is not currently usable from outside the CPython
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implementation, as it must be called prior to the implicit import of
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:mod:`warnings` in :c:func:`Py_Initialize` to be effective, but can't be
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called until enough of the runtime has been initialized to permit the
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creation of Unicode objects.
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.. c:function:: void PySys_SetPath(const wchar_t *path)
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Set :data:`sys.path` to a list object of paths found in *path* which should
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be a list of paths separated with the platform's search path delimiter
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(``:`` on Unix, ``;`` on Windows).
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.. c:function:: void PySys_WriteStdout(const char *format, ...)
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Write the output string described by *format* to :data:`sys.stdout`. No
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exceptions are raised, even if truncation occurs (see below).
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*format* should limit the total size of the formatted output string to
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1000 bytes or less -- after 1000 bytes, the output string is truncated.
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In particular, this means that no unrestricted "%s" formats should occur;
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these should be limited using "%.<N>s" where <N> is a decimal number
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calculated so that <N> plus the maximum size of other formatted text does not
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exceed 1000 bytes. Also watch out for "%f", which can print hundreds of
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digits for very large numbers.
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If a problem occurs, or :data:`sys.stdout` is unset, the formatted message
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is written to the real (C level) *stdout*.
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.. c:function:: void PySys_WriteStderr(const char *format, ...)
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As :c:func:`PySys_WriteStdout`, but write to :data:`sys.stderr` or *stderr*
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instead.
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.. c:function:: void PySys_FormatStdout(const char *format, ...)
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Function similar to PySys_WriteStdout() but format the message using
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:c:func:`PyUnicode_FromFormatV` and don't truncate the message to an
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arbitrary length.
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.. versionadded:: 3.2
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.. c:function:: void PySys_FormatStderr(const char *format, ...)
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As :c:func:`PySys_FormatStdout`, but write to :data:`sys.stderr` or *stderr*
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instead.
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.. versionadded:: 3.2
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.. c:function:: void PySys_AddXOption(const wchar_t *s)
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Parse *s* as a set of :option:`-X` options and add them to the current
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options mapping as returned by :c:func:`PySys_GetXOptions`. This function
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may be called prior to :c:func:`Py_Initialize`.
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.. versionadded:: 3.2
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.. c:function:: PyObject *PySys_GetXOptions()
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Return the current dictionary of :option:`-X` options, similarly to
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:data:`sys._xoptions`. On error, ``NULL`` is returned and an exception is
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set.
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.. versionadded:: 3.2
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.. c:function:: int PySys_Audit(const char *event, const char *format, ...)
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Raise an auditing event with any active hooks. Return zero for success
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and non-zero with an exception set on failure.
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If any hooks have been added, *format* and other arguments will be used
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to construct a tuple to pass. Apart from ``N``, the same format characters
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as used in :c:func:`Py_BuildValue` are available. If the built value is not
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a tuple, it will be added into a single-element tuple. (The ``N`` format
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option consumes a reference, but since there is no way to know whether
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arguments to this function will be consumed, using it may cause reference
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leaks.)
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Note that ``#`` format characters should always be treated as
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``Py_ssize_t``, regardless of whether ``PY_SSIZE_T_CLEAN`` was defined.
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:func:`sys.audit` performs the same function from Python code.
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.. versionadded:: 3.8
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.. versionchanged:: 3.8.2
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Require ``Py_ssize_t`` for ``#`` format characters. Previously, an
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unavoidable deprecation warning was raised.
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.. c:function:: int PySys_AddAuditHook(Py_AuditHookFunction hook, void *userData)
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Append the callable *hook* to the list of active auditing hooks.
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Return zero for success
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and non-zero on failure. If the runtime has been initialized, also set an
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error on failure. Hooks added through this API are called for all
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interpreters created by the runtime.
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The *userData* pointer is passed into the hook function. Since hook
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functions may be called from different runtimes, this pointer should not
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refer directly to Python state.
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This function is safe to call before :c:func:`Py_Initialize`. When called
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after runtime initialization, existing audit hooks are notified and may
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silently abort the operation by raising an error subclassed from
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:class:`Exception` (other errors will not be silenced).
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The hook function is of type :c:type:`int (*)(const char *event, PyObject
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*args, void *userData)`, where *args* is guaranteed to be a
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:c:type:`PyTupleObject`. The hook function is always called with the GIL
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held by the Python interpreter that raised the event.
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See :pep:`578` for a detailed description of auditing. Functions in the
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runtime and standard library that raise events are listed in the
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:ref:`audit events table <audit-events>`.
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Details are in each function's documentation.
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.. audit-event:: sys.addaudithook "" c.PySys_AddAuditHook
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If the interpreter is initialized, this function raises a auditing event
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``sys.addaudithook`` with no arguments. If any existing hooks raise an
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exception derived from :class:`Exception`, the new hook will not be
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added and the exception is cleared. As a result, callers cannot assume
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that their hook has been added unless they control all existing hooks.
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.. versionadded:: 3.8
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.. _processcontrol:
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Process Control
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===============
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.. c:function:: void Py_FatalError(const char *message)
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.. index:: single: abort()
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Print a fatal error message and kill the process. No cleanup is performed.
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This function should only be invoked when a condition is detected that would
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make it dangerous to continue using the Python interpreter; e.g., when the
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object administration appears to be corrupted. On Unix, the standard C library
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function :c:func:`abort` is called which will attempt to produce a :file:`core`
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file.
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The ``Py_FatalError()`` function is replaced with a macro which logs
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automatically the name of the current function, unless the
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``Py_LIMITED_API`` macro is defined.
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.. versionchanged:: 3.9
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Log the function name automatically.
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.. c:function:: void Py_Exit(int status)
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.. index::
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single: Py_FinalizeEx()
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single: exit()
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Exit the current process. This calls :c:func:`Py_FinalizeEx` and then calls the
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standard C library function ``exit(status)``. If :c:func:`Py_FinalizeEx`
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indicates an error, the exit status is set to 120.
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.. versionchanged:: 3.6
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Errors from finalization no longer ignored.
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.. c:function:: int Py_AtExit(void (*func) ())
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.. index::
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single: Py_FinalizeEx()
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single: cleanup functions
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Register a cleanup function to be called by :c:func:`Py_FinalizeEx`. The cleanup
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function will be called with no arguments and should return no value. At most
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32 cleanup functions can be registered. When the registration is successful,
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:c:func:`Py_AtExit` returns ``0``; on failure, it returns ``-1``. The cleanup
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function registered last is called first. Each cleanup function will be called
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at most once. Since Python's internal finalization will have completed before
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the cleanup function, no Python APIs should be called by *func*.
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