Operating System Utilities

PyObject*PyOS_FSPath(PyObject *path)
Return value: New reference.

Return the file system representation forpath. If the object is astr orbytes object, then its reference count isincremented. If the object implements theos.PathLike interface,then__fspath__() is returned as long as it is astr orbytes object. OtherwiseTypeError is raisedandNULL is returned.

New in version 3.6.

intPy_FdIsInteractive(FILE *fp, const char *filename)

Return true (nonzero) if the standard I/O filefp with namefilename isdeemed interactive. This is the case for files for whichisatty(fileno(fp))is true. If the global flagPy_InteractiveFlag is true, this functionalso returns true if thefilename pointer isNULL or if the name is equal toone of the strings'<stdin>' or'???'.

voidPyOS_BeforeFork()

Function to prepare some internal state before a process fork. Thisshould be called before callingfork() or any similar functionthat clones the current process.Only available on systems wherefork() is defined.

New in version 3.7.

voidPyOS_AfterFork_Parent()

Function to update some internal state after a process fork. Thisshould be called from the parent process after callingfork()or any similar function that clones the current process, regardlessof whether process cloning was successful.Only available on systems wherefork() is defined.

New in version 3.7.

voidPyOS_AfterFork_Child()

Function to update internal interpreter state after a process fork.This must be called from the child process after callingfork(),or any similar function that clones the current process, if there isany chance the process will call back into the Python interpreter.Only available on systems wherefork() is defined.

New in version 3.7.

See also

os.register_at_fork() allows registering custom Python functionsto be called byPyOS_BeforeFork(),PyOS_AfterFork_Parent() andPyOS_AfterFork_Child().

voidPyOS_AfterFork()

Function to update some internal state after a process fork; this should becalled in the new process if the Python interpreter will continue to be used.If a new executable is loaded into the new process, this function does not needto be called.

Deprecated since version 3.7:This function is superseded byPyOS_AfterFork_Child().

intPyOS_CheckStack()

Return true when the interpreter runs out of stack space. This is a reliablecheck, but is only available whenUSE_STACKCHECK is defined (currentlyon Windows using the Microsoft Visual C++ compiler).USE_STACKCHECKwill be defined automatically; you should never change the definition in yourown code.

PyOS_sighandler_tPyOS_getsig(int i)

Return the current signal handler for signali. This is a thin wrapper aroundeithersigaction() orsignal(). Do not call those functionsdirectly!PyOS_sighandler_t is a typedef alias forvoid(*)(int).

PyOS_sighandler_tPyOS_setsig(int i, PyOS_sighandler_t h)

Set the signal handler for signali to beh; return the old signal handler.This is a thin wrapper around eithersigaction() orsignal(). Donot call those functions directly!PyOS_sighandler_t is a typedefalias forvoid(*)(int).

wchar_t*Py_DecodeLocale(const char* arg, size_t *size)

Decode a byte string from the locale encoding with thesurrogateescapeerror handler: undecodable bytes are decoded ascharacters in range U+DC80..U+DCFF. If a byte sequence can be decoded as asurrogate character, escape the bytes using the surrogateescape errorhandler instead of decoding them.

Encoding, highest priority to lowest priority:

  • UTF-8 on macOS and Android;

  • UTF-8 if the Python UTF-8 mode is enabled;

  • ASCII if theLC_CTYPE locale is"C",nl_langinfo(CODESET) returns theASCII encoding (or an alias),andmbstowcs() andwcstombs() functions uses theISO-8859-1 encoding.

  • the current locale encoding.

Return a pointer to a newly allocated wide character string, usePyMem_RawFree() to free the memory. If size is notNULL, writethe number of wide characters excluding the null character into*size

ReturnNULL on decoding error or memory allocation error. Ifsize isnotNULL,*size is set to(size_t)-1 on memory error or set to(size_t)-2 on decoding error.

Decoding errors should never happen, unless there is a bug in the Clibrary.

Use thePy_EncodeLocale() function to encode the character stringback to a byte string.

New in version 3.5.

Changed in version 3.7:The function now uses the UTF-8 encoding in the UTF-8 mode.

char*Py_EncodeLocale(const wchar_t *text, size_t *error_pos)

Encode a wide character string to the locale encoding with thesurrogateescape error handler: surrogate charactersin the range U+DC80..U+DCFF are converted to bytes 0x80..0xFF.

Encoding, highest priority to lowest priority:

  • UTF-8 on macOS and Android;

  • UTF-8 if the Python UTF-8 mode is enabled;

  • ASCII if theLC_CTYPE locale is"C",nl_langinfo(CODESET) returns theASCII encoding (or an alias),andmbstowcs() andwcstombs() functions uses theISO-8859-1 encoding.

  • the current locale encoding.

The function uses the UTF-8 encoding in the Python UTF-8 mode.

Return a pointer to a newly allocated byte string, usePyMem_Free()to free the memory. ReturnNULL on encoding error or memory allocationerror

If error_pos is notNULL,*error_pos is set to(size_t)-1 onsuccess, or set to the index of the invalid character on encoding error.

Use thePy_DecodeLocale() function to decode the bytes string backto a wide character string.

Changed in version 3.7:The function now uses the UTF-8 encoding in the UTF-8 mode.

New in version 3.5.

Changed in version 3.7:The function now supports the UTF-8 mode.

System Functions

These are utility functions that make functionality from thesys moduleaccessible to C code. They all work with the current interpreter thread’ssys module’s dict, which is contained in the internal thread state structure.

PyObject *PySys_GetObject(const char *name)
Return value: Borrowed reference.

Return the objectname from thesys module orNULL if it doesnot exist, without setting an exception.

intPySys_SetObject(const char *name,PyObject *v)

Setname in thesys module tov unlessv isNULL, in whichcasename is deleted from the sys module. Returns0 on success,-1on error.

voidPySys_ResetWarnOptions()

Resetsys.warnoptions to an empty list. This function may becalled prior toPy_Initialize().

voidPySys_AddWarnOption(const wchar_t *s)

Appends tosys.warnoptions. This function must be called priortoPy_Initialize() in order to affect the warnings filter list.

voidPySys_AddWarnOptionUnicode(PyObject *unicode)

Appendunicode tosys.warnoptions.

Note: this function is not currently usable from outside the CPythonimplementation, as it must be called prior to the implicit import ofwarnings inPy_Initialize() to be effective, but can’t becalled until enough of the runtime has been initialized to permit thecreation of Unicode objects.

voidPySys_SetPath(const wchar_t *path)

Setsys.path to a list object of paths found inpath which shouldbe a list of paths separated with the platform’s search path delimiter(: on Unix,; on Windows).

voidPySys_WriteStdout(const char *format, ...)

Write the output string described byformat tosys.stdout. Noexceptions are raised, even if truncation occurs (see below).

format should limit the total size of the formatted output string to1000 bytes or less – after 1000 bytes, the output string is truncated.In particular, this means that no unrestricted “%s” formats should occur;these should be limited using “%.<N>s” where <N> is a decimal numbercalculated so that <N> plus the maximum size of other formatted text does notexceed 1000 bytes. Also watch out for “%f”, which can print hundreds ofdigits for very large numbers.

If a problem occurs, orsys.stdout is unset, the formatted messageis written to the real (C level)stdout.

voidPySys_WriteStderr(const char *format, ...)

AsPySys_WriteStdout(), but write tosys.stderr orstderrinstead.

voidPySys_FormatStdout(const char *format, ...)

Function similar to PySys_WriteStdout() but format the message usingPyUnicode_FromFormatV() and don’t truncate the message to anarbitrary length.

New in version 3.2.

voidPySys_FormatStderr(const char *format, ...)

AsPySys_FormatStdout(), but write tosys.stderr orstderrinstead.

New in version 3.2.

voidPySys_AddXOption(const wchar_t *s)

Parses as a set of-X options and add them to the currentoptions mapping as returned byPySys_GetXOptions(). This functionmay be called prior toPy_Initialize().

New in version 3.2.

PyObject *PySys_GetXOptions()
Return value: Borrowed reference.

Return the current dictionary of-X options, similarly tosys._xoptions. On error,NULL is returned and an exception isset.

New in version 3.2.

Process Control

voidPy_FatalError(const char *message)

Print a fatal error message and kill the process. No cleanup is performed.This function should only be invoked when a condition is detected that wouldmake it dangerous to continue using the Python interpreter; e.g., when theobject administration appears to be corrupted. On Unix, the standard C libraryfunctionabort() is called which will attempt to produce acorefile.

voidPy_Exit(int status)

Exit the current process. This callsPy_FinalizeEx() and then calls thestandard C library functionexit(status). IfPy_FinalizeEx()indicates an error, the exit status is set to 120.

Changed in version 3.6:Errors from finalization no longer ignored.

intPy_AtExit(void (*func)())

Register a cleanup function to be called byPy_FinalizeEx(). The cleanupfunction will be called with no arguments and should return no value. At most32 cleanup functions can be registered. When the registration is successful,Py_AtExit() returns0; on failure, it returns-1. The cleanupfunction registered last is called first. Each cleanup function will be calledat most once. Since Python’s internal finalization will have completed beforethe cleanup function, no Python APIs should be called byfunc.