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+.. highlightlang:: c
+
+
+.. _utilities:
+
+*********
+Utilities
+*********
+
+The functions in this chapter perform various utility tasks, ranging from
+helping C code be more portable across platforms, using Python modules from C,
+and parsing function arguments and constructing Python values from C values.
+
+
+.. _os:
+
+Operating System Utilities
+==========================
+
+
+.. cfunction:: int Py_FdIsInteractive(FILE *fp, const char *filename)
+
+   Return true (nonzero) if the standard I/O file *fp* with name *filename* is
+   deemed interactive.  This is the case for files for which ``isatty(fileno(fp))``
+   is true.  If the global flag :cdata:`Py_InteractiveFlag` is true, this function
+   also returns true if the *filename* pointer is *NULL* or if the name is equal to
+   one of the strings ``'<stdin>'`` or ``'???'``.
+
+
+.. cfunction:: long PyOS_GetLastModificationTime(char *filename)
+
+   Return the time of last modification of the file *filename*. The result is
+   encoded in the same way as the timestamp returned by the standard C library
+   function :cfunc:`time`.
+
+
+.. cfunction:: void PyOS_AfterFork()
+
+   Function to update some internal state after a process fork; this should be
+   called 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 need
+   to be called.
+
+
+.. cfunction:: int PyOS_CheckStack()
+
+   Return true when the interpreter runs out of stack space.  This is a reliable
+   check, but is only available when :const:`USE_STACKCHECK` is defined (currently
+   on Windows using the Microsoft Visual C++ compiler).  :const:`USE_STACKCHECK`
+   will be defined automatically; you should never change the definition in your
+   own code.
+
+
+.. cfunction:: PyOS_sighandler_t PyOS_getsig(int i)
+
+   Return the current signal handler for signal *i*.  This is a thin wrapper around
+   either :cfunc:`sigaction` or :cfunc:`signal`.  Do not call those functions
+   directly! :ctype:`PyOS_sighandler_t` is a typedef alias for :ctype:`void
+   (\*)(int)`.
+
+
+.. cfunction:: PyOS_sighandler_t PyOS_setsig(int i, PyOS_sighandler_t h)
+
+   Set the signal handler for signal *i* to be *h*; return the old signal handler.
+   This is a thin wrapper around either :cfunc:`sigaction` or :cfunc:`signal`.  Do
+   not call those functions directly!  :ctype:`PyOS_sighandler_t` is a typedef
+   alias for :ctype:`void (\*)(int)`.
+
+
+.. _processcontrol:
+
+Process Control
+===============
+
+
+.. cfunction:: void Py_FatalError(const char *message)
+
+   .. index:: single: abort()
+
+   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 would
+   make it dangerous to continue using the Python interpreter; e.g., when the
+   object administration appears to be corrupted.  On Unix, the standard C library
+   function :cfunc:`abort` is called which will attempt to produce a :file:`core`
+   file.
+
+
+.. cfunction:: void Py_Exit(int status)
+
+   .. index::
+      single: Py_Finalize()
+      single: exit()
+
+   Exit the current process.  This calls :cfunc:`Py_Finalize` and then calls the
+   standard C library function ``exit(status)``.
+
+
+.. cfunction:: int Py_AtExit(void (*func) ())
+
+   .. index::
+      single: Py_Finalize()
+      single: cleanup functions
+
+   Register a cleanup function to be called by :cfunc:`Py_Finalize`.  The cleanup
+   function will be called with no arguments and should return no value.  At most
+   32 cleanup functions can be registered.  When the registration is successful,
+   :cfunc:`Py_AtExit` returns ``0``; on failure, it returns ``-1``.  The cleanup
+   function registered last is called first. Each cleanup function will be called
+   at most once.  Since Python's internal finalization will have completed before
+   the cleanup function, no Python APIs should be called by *func*.
+
+
+.. _importing:
+
+Importing Modules
+=================
+
+
+.. cfunction:: PyObject* PyImport_ImportModule(const char *name)
+
+   .. index::
+      single: package variable; __all__
+      single: __all__ (package variable)
+
+   This is a simplified interface to :cfunc:`PyImport_ImportModuleEx` below,
+   leaving the *globals* and *locals* arguments set to *NULL*.  When the *name*
+   argument contains a dot (when it specifies a submodule of a package), the
+   *fromlist* argument is set to the list ``['*']`` so that the return value is the
+   named module rather than the top-level package containing it as would otherwise
+   be the case.  (Unfortunately, this has an additional side effect when *name* in
+   fact specifies a subpackage instead of a submodule: the submodules specified in
+   the package's ``__all__`` variable are  loaded.)  Return a new reference to the
+   imported module, or *NULL* with an exception set on failure.  Before Python 2.4,
+   the module may still be created in the failure case --- examine ``sys.modules``
+   to find out.  Starting with Python 2.4, a failing import of a module no longer
+   leaves the module in ``sys.modules``.
+
+   .. versionchanged:: 2.4
+      failing imports remove incomplete module objects.
+
+   .. index:: single: modules (in module sys)
+
+
+.. cfunction:: PyObject* PyImport_ImportModuleEx(char *name, PyObject *globals, PyObject *locals, PyObject *fromlist)
+
+   .. index:: builtin: __import__
+
+   Import a module.  This is best described by referring to the built-in Python
+   function :func:`__import__`, as the standard :func:`__import__` function calls
+   this function directly.
+
+   The return value is a new reference to the imported module or top-level package,
+   or *NULL* with an exception set on failure (before Python 2.4, the module may
+   still be created in this case).  Like for :func:`__import__`, the return value
+   when a submodule of a package was requested is normally the top-level package,
+   unless a non-empty *fromlist* was given.
+
+   .. versionchanged:: 2.4
+      failing imports remove incomplete module objects.
+
+
+.. cfunction:: PyObject* PyImport_Import(PyObject *name)
+
+   .. index::
+      module: rexec
+      module: ihooks
+
+   This is a higher-level interface that calls the current "import hook function".
+   It invokes the :func:`__import__` function from the ``__builtins__`` of the
+   current globals.  This means that the import is done using whatever import hooks
+   are installed in the current environment, e.g. by :mod:`rexec` or :mod:`ihooks`.
+
+
+.. cfunction:: PyObject* PyImport_ReloadModule(PyObject *m)
+
+   Reload a module.  Return a new reference to the reloaded module, or *NULL* with
+   an exception set on failure (the module still exists in this case).
+
+
+.. cfunction:: PyObject* PyImport_AddModule(const char *name)
+
+   Return the module object corresponding to a module name.  The *name* argument
+   may be of the form ``package.module``. First check the modules dictionary if
+   there's one there, and if not, create a new one and insert it in the modules
+   dictionary. Return *NULL* with an exception set on failure.
+
+   .. note::
+
+      This function does not load or import the module; if the module wasn't already
+      loaded, you will get an empty module object. Use :cfunc:`PyImport_ImportModule`
+      or one of its variants to import a module.  Package structures implied by a
+      dotted name for *name* are not created if not already present.
+
+
+.. cfunction:: PyObject* PyImport_ExecCodeModule(char *name, PyObject *co)
+
+   .. index:: builtin: compile
+
+   Given a module name (possibly of the form ``package.module``) and a code object
+   read from a Python bytecode file or obtained from the built-in function
+   :func:`compile`, load the module.  Return a new reference to the module object,
+   or *NULL* with an exception set if an error occurred.  Before Python 2.4, the
+   module could still be created in error cases.  Starting with Python 2.4, *name*
+   is removed from ``sys.modules`` in error cases, and even if *name* was already
+   in ``sys.modules`` on entry to :cfunc:`PyImport_ExecCodeModule`.  Leaving
+   incompletely initialized modules in ``sys.modules`` is dangerous, as imports of
+   such modules have no way to know that the module object is an unknown (and
+   probably damaged with respect to the module author's intents) state.
+
+   This function will reload the module if it was already imported.  See
+   :cfunc:`PyImport_ReloadModule` for the intended way to reload a module.
+
+   If *name* points to a dotted name of the form ``package.module``, any package
+   structures not already created will still not be created.
+
+   .. versionchanged:: 2.4
+      *name* is removed from ``sys.modules`` in error cases.
+
+
+.. cfunction:: long PyImport_GetMagicNumber()
+
+   Return the magic number for Python bytecode files (a.k.a. :file:`.pyc` and
+   :file:`.pyo` files).  The magic number should be present in the first four bytes
+   of the bytecode file, in little-endian byte order.
+
+
+.. cfunction:: PyObject* PyImport_GetModuleDict()
+
+   Return the dictionary used for the module administration (a.k.a.
+   ``sys.modules``).  Note that this is a per-interpreter variable.
+
+
+.. cfunction:: void _PyImport_Init()
+
+   Initialize the import mechanism.  For internal use only.
+
+
+.. cfunction:: void PyImport_Cleanup()
+
+   Empty the module table.  For internal use only.
+
+
+.. cfunction:: void _PyImport_Fini()
+
+   Finalize the import mechanism.  For internal use only.
+
+
+.. cfunction:: PyObject* _PyImport_FindExtension(char *, char *)
+
+   For internal use only.
+
+
+.. cfunction:: PyObject* _PyImport_FixupExtension(char *, char *)
+
+   For internal use only.
+
+
+.. cfunction:: int PyImport_ImportFrozenModule(char *name)
+
+   Load a frozen module named *name*.  Return ``1`` for success, ``0`` if the
+   module is not found, and ``-1`` with an exception set if the initialization
+   failed.  To access the imported module on a successful load, use
+   :cfunc:`PyImport_ImportModule`.  (Note the misnomer --- this function would
+   reload the module if it was already imported.)
+
+
+.. ctype:: struct _frozen
+
+   .. index:: single: freeze utility
+
+   This is the structure type definition for frozen module descriptors, as
+   generated by the :program:`freeze` utility (see :file:`Tools/freeze/` in the
+   Python source distribution).  Its definition, found in :file:`Include/import.h`,
+   is::
+
+      struct _frozen {
+          char *name;
+          unsigned char *code;
+          int size;
+      };
+
+
+.. cvar:: struct _frozen* PyImport_FrozenModules
+
+   This pointer is initialized to point to an array of :ctype:`struct _frozen`
+   records, terminated by one whose members are all *NULL* or zero.  When a frozen
+   module is imported, it is searched in this table.  Third-party code could play
+   tricks with this to provide a dynamically created collection of frozen modules.
+
+
+.. cfunction:: int PyImport_AppendInittab(char *name, void (*initfunc)(void))
+
+   Add a single module to the existing table of built-in modules.  This is a
+   convenience wrapper around :cfunc:`PyImport_ExtendInittab`, returning ``-1`` if
+   the table could not be extended.  The new module can be imported by the name
+   *name*, and uses the function *initfunc* as the initialization function called
+   on the first attempted import.  This should be called before
+   :cfunc:`Py_Initialize`.
+
+
+.. ctype:: struct _inittab
+
+   Structure describing a single entry in the list of built-in modules.  Each of
+   these structures gives the name and initialization function for a module built
+   into the interpreter.  Programs which embed Python may use an array of these
+   structures in conjunction with :cfunc:`PyImport_ExtendInittab` to provide
+   additional built-in modules.  The structure is defined in
+   :file:`Include/import.h` as::
+
+      struct _inittab {
+          char *name;
+          void (*initfunc)(void);
+      };
+
+
+.. cfunction:: int PyImport_ExtendInittab(struct _inittab *newtab)
+
+   Add a collection of modules to the table of built-in modules.  The *newtab*
+   array must end with a sentinel entry which contains *NULL* for the :attr:`name`
+   field; failure to provide the sentinel value can result in a memory fault.
+   Returns ``0`` on success or ``-1`` if insufficient memory could be allocated to
+   extend the internal table.  In the event of failure, no modules are added to the
+   internal table.  This should be called before :cfunc:`Py_Initialize`.
+
+
+.. _marshalling-utils:
+
+Data marshalling support
+========================
+
+These routines allow C code to work with serialized objects using the same data
+format as the :mod:`marshal` module.  There are functions to write data into the
+serialization format, and additional functions that can be used to read the data
+back.  Files used to store marshalled data must be opened in binary mode.
+
+Numeric values are stored with the least significant byte first.
+
+The module supports two versions of the data format: version 0 is the historical
+version, version 1 (new in Python 2.4) shares interned strings in the file, and
+upon unmarshalling. *Py_MARSHAL_VERSION* indicates the current file format
+(currently 1).
+
+
+.. cfunction:: void PyMarshal_WriteLongToFile(long value, FILE *file, int version)
+
+   Marshal a :ctype:`long` integer, *value*, to *file*.  This will only write the
+   least-significant 32 bits of *value*; regardless of the size of the native
+   :ctype:`long` type.
+
+   .. versionchanged:: 2.4
+      *version* indicates the file format.
+
+
+.. cfunction:: void PyMarshal_WriteObjectToFile(PyObject *value, FILE *file, int version)
+
+   Marshal a Python object, *value*, to *file*.
+
+   .. versionchanged:: 2.4
+      *version* indicates the file format.
+
+
+.. cfunction:: PyObject* PyMarshal_WriteObjectToString(PyObject *value, int version)
+
+   Return a string object containing the marshalled representation of *value*.
+
+   .. versionchanged:: 2.4
+      *version* indicates the file format.
+
+
+The following functions allow marshalled values to be read back in.
+
+XXX What about error detection?  It appears that reading past the end of the
+file will always result in a negative numeric value (where that's relevant), but
+it's not clear that negative values won't be handled properly when there's no
+error.  What's the right way to tell? Should only non-negative values be written
+using these routines?
+
+
+.. cfunction:: long PyMarshal_ReadLongFromFile(FILE *file)
+
+   Return a C :ctype:`long` from the data stream in a :ctype:`FILE\*` opened for
+   reading.  Only a 32-bit value can be read in using this function, regardless of
+   the native size of :ctype:`long`.
+
+
+.. cfunction:: int PyMarshal_ReadShortFromFile(FILE *file)
+
+   Return a C :ctype:`short` from the data stream in a :ctype:`FILE\*` opened for
+   reading.  Only a 16-bit value can be read in using this function, regardless of
+   the native size of :ctype:`short`.
+
+
+.. cfunction:: PyObject* PyMarshal_ReadObjectFromFile(FILE *file)
+
+   Return a Python object from the data stream in a :ctype:`FILE\*` opened for
+   reading.  On error, sets the appropriate exception (:exc:`EOFError` or
+   :exc:`TypeError`) and returns *NULL*.
+
+
+.. cfunction:: PyObject* PyMarshal_ReadLastObjectFromFile(FILE *file)
+
+   Return a Python object from the data stream in a :ctype:`FILE\*` opened for
+   reading.  Unlike :cfunc:`PyMarshal_ReadObjectFromFile`, this function assumes
+   that no further objects will be read from the file, allowing it to aggressively
+   load file data into memory so that the de-serialization can operate from data in
+   memory rather than reading a byte at a time from the file.  Only use these
+   variant if you are certain that you won't be reading anything else from the
+   file.  On error, sets the appropriate exception (:exc:`EOFError` or
+   :exc:`TypeError`) and returns *NULL*.
+
+
+.. cfunction:: PyObject* PyMarshal_ReadObjectFromString(char *string, Py_ssize_t len)
+
+   Return a Python object from the data stream in a character buffer containing
+   *len* bytes pointed to by *string*.  On error, sets the appropriate exception
+   (:exc:`EOFError` or :exc:`TypeError`) and returns *NULL*.
+
+
+.. _arg-parsing:
+
+Parsing arguments and building values
+=====================================
+
+These functions are useful when creating your own extensions functions and
+methods.  Additional information and examples are available in
+:ref:`extending-index`.
+
+The first three of these functions described, :cfunc:`PyArg_ParseTuple`,
+:cfunc:`PyArg_ParseTupleAndKeywords`, and :cfunc:`PyArg_Parse`, all use *format
+strings* which are used to tell the function about the expected arguments.  The
+format strings use the same syntax for each of these functions.
+
+A format string consists of zero or more "format units."  A format unit
+describes one Python object; it is usually a single character or a parenthesized
+sequence of format units.  With a few exceptions, a format unit that is not a
+parenthesized sequence normally corresponds to a single address argument to
+these functions.  In the following description, the quoted form is the format
+unit; the entry in (round) parentheses is the Python object type that matches
+the format unit; and the entry in [square] brackets is the type of the C
+variable(s) whose address should be passed.
+
+``s`` (string or Unicode object) [const char \*]
+   Convert a Python string or Unicode object to a C pointer to a character string.
+   You must not provide storage for the string itself; a pointer to an existing
+   string is stored into the character pointer variable whose address you pass.
+   The C string is NUL-terminated.  The Python string must not contain embedded NUL
+   bytes; if it does, a :exc:`TypeError` exception is raised. Unicode objects are
+   converted to C strings using the default encoding.  If this conversion fails, a
+   :exc:`UnicodeError` is raised.
+
+``s#`` (string, Unicode or any read buffer compatible object) [const char \*, int]
+   This variant on ``s`` stores into two C variables, the first one a pointer to a
+   character string, the second one its length.  In this case the Python string may
+   contain embedded null bytes.  Unicode objects pass back a pointer to the default
+   encoded string version of the object if such a conversion is possible.  All
+   other read-buffer compatible objects pass back a reference to the raw internal
+   data representation.
+
+``y`` (bytes object) [const char \*]
+   This variant on ``s`` convert a Python bytes object to a C pointer to a
+   character string. The bytes object must not contain embedded NUL bytes; if it
+   does, a :exc:`TypeError` exception is raised.
+
+``y#`` (bytes object) [const char \*, int]
+   This variant on ``s#`` stores into two C variables, the first one a pointer to a
+   character string, the second one its length.  This only accepts bytes objects.
+
+``z`` (string or ``None``) [const char \*]
+   Like ``s``, but the Python object may also be ``None``, in which case the C
+   pointer is set to *NULL*.
+
+``z#`` (string or ``None`` or any read buffer compatible object) [const char \*, int]
+   This is to ``s#`` as ``z`` is to ``s``.
+
+``u`` (Unicode object) [Py_UNICODE \*]
+   Convert a Python Unicode object to a C pointer to a NUL-terminated buffer of
+   16-bit Unicode (UTF-16) data.  As with ``s``, there is no need to provide
+   storage for the Unicode data buffer; a pointer to the existing Unicode data is
+   stored into the :ctype:`Py_UNICODE` pointer variable whose address you pass.
+
+``u#`` (Unicode object) [Py_UNICODE \*, int]
+   This variant on ``u`` stores into two C variables, the first one a pointer to a
+   Unicode data buffer, the second one its length. Non-Unicode objects are handled
+   by interpreting their read-buffer pointer as pointer to a :ctype:`Py_UNICODE`
+   array.
+
+``es`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer]
+   This variant on ``s`` is used for encoding Unicode and objects convertible to
+   Unicode into a character buffer. It only works for encoded data without embedded
+   NUL bytes.
+
+   This format requires two arguments.  The first is only used as input, and
+   must be a :ctype:`const char\*` which points to the name of an encoding as a
+   NUL-terminated string, or *NULL*, in which case the default encoding is used.
+   An exception is raised if the named encoding is not known to Python.  The
+   second argument must be a :ctype:`char\*\*`; the value of the pointer it
+   references will be set to a buffer with the contents of the argument text.
+   The text will be encoded in the encoding specified by the first argument.
+
+   :cfunc:`PyArg_ParseTuple` will allocate a buffer of the needed size, copy the
+   encoded data into this buffer and adjust *\*buffer* to reference the newly
+   allocated storage.  The caller is responsible for calling :cfunc:`PyMem_Free` to
+   free the allocated buffer after use.
+
+``et`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer]
+   Same as ``es`` except that 8-bit string objects are passed through without
+   recoding them.  Instead, the implementation assumes that the string object uses
+   the encoding passed in as parameter.
+
+``es#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer, int \*buffer_length]
+   This variant on ``s#`` is used for encoding Unicode and objects convertible to
+   Unicode into a character buffer.  Unlike the ``es`` format, this variant allows
+   input data which contains NUL characters.
+
+   It requires three arguments.  The first is only used as input, and must be a
+   :ctype:`const char\*` which points to the name of an encoding as a
+   NUL-terminated string, or *NULL*, in which case the default encoding is used.
+   An exception is raised if the named encoding is not known to Python.  The
+   second argument must be a :ctype:`char\*\*`; the value of the pointer it
+   references will be set to a buffer with the contents of the argument text.
+   The text will be encoded in the encoding specified by the first argument.
+   The third argument must be a pointer to an integer; the referenced integer
+   will be set to the number of bytes in the output buffer.
+
+   There are two modes of operation:
+
+   If *\*buffer* points a *NULL* pointer, the function will allocate a buffer of
+   the needed size, copy the encoded data into this buffer and set *\*buffer* to
+   reference the newly allocated storage.  The caller is responsible for calling
+   :cfunc:`PyMem_Free` to free the allocated buffer after usage.
+
+   If *\*buffer* points to a non-*NULL* pointer (an already allocated buffer),
+   :cfunc:`PyArg_ParseTuple` will use this location as the buffer and interpret the
+   initial value of *\*buffer_length* as the buffer size.  It will then copy the
+   encoded data into the buffer and NUL-terminate it.  If the buffer is not large
+   enough, a :exc:`ValueError` will be set.
+
+   In both cases, *\*buffer_length* is set to the length of the encoded data
+   without the trailing NUL byte.
+
+``et#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer]
+   Same as ``es#`` except that string objects are passed through without recoding
+   them. Instead, the implementation assumes that the string object uses the
+   encoding passed in as parameter.
+
+``b`` (integer) [char]
+   Convert a Python integer to a tiny int, stored in a C :ctype:`char`.
+
+``B`` (integer) [unsigned char]
+   Convert a Python integer to a tiny int without overflow checking, stored in a C
+   :ctype:`unsigned char`.
+
+   .. versionadded:: 2.3
+
+``h`` (integer) [short int]
+   Convert a Python integer to a C :ctype:`short int`.
+
+``H`` (integer) [unsigned short int]
+   Convert a Python integer to a C :ctype:`unsigned short int`, without overflow
+   checking.
+
+   .. versionadded:: 2.3
+
+``i`` (integer) [int]
+   Convert a Python integer to a plain C :ctype:`int`.
+
+``I`` (integer) [unsigned int]
+   Convert a Python integer to a C :ctype:`unsigned int`, without overflow
+   checking.
+
+   .. versionadded:: 2.3
+
+``l`` (integer) [long int]
+   Convert a Python integer to a C :ctype:`long int`.
+
+``k`` (integer) [unsigned long]
+   Convert a Python integer or long integer to a C :ctype:`unsigned long` without
+   overflow checking.
+
+   .. versionadded:: 2.3
+
+``L`` (integer) [PY_LONG_LONG]
+   Convert a Python integer to a C :ctype:`long long`.  This format is only
+   available on platforms that support :ctype:`long long` (or :ctype:`_int64` on
+   Windows).
+
+``K`` (integer) [unsigned PY_LONG_LONG]
+   Convert a Python integer or long integer to a C :ctype:`unsigned long long`
+   without overflow checking.  This format is only available on platforms that
+   support :ctype:`unsigned long long` (or :ctype:`unsigned _int64` on Windows).
+
+   .. versionadded:: 2.3
+
+``n`` (integer) [Py_ssize_t]
+   Convert a Python integer or long integer to a C :ctype:`Py_ssize_t`.
+
+   .. versionadded:: 2.5
+
+``c`` (string of length 1) [char]
+   Convert a Python character, represented as a string of length 1, to a C
+   :ctype:`char`.
+
+``f`` (float) [float]
+   Convert a Python floating point number to a C :ctype:`float`.
+
+``d`` (float) [double]
+   Convert a Python floating point number to a C :ctype:`double`.
+
+``D`` (complex) [Py_complex]
+   Convert a Python complex number to a C :ctype:`Py_complex` structure.
+
+``O`` (object) [PyObject \*]
+   Store a Python object (without any conversion) in a C object pointer.  The C
+   program thus receives the actual object that was passed.  The object's reference
+   count is not increased.  The pointer stored is not *NULL*.
+
+``O!`` (object) [*typeobject*, PyObject \*]
+   Store a Python object in a C object pointer.  This is similar to ``O``, but
+   takes two C arguments: the first is the address of a Python type object, the
+   second is the address of the C variable (of type :ctype:`PyObject\*`) into which
+   the object pointer is stored.  If the Python object does not have the required
+   type, :exc:`TypeError` is raised.
+
+``O&`` (object) [*converter*, *anything*]
+   Convert a Python object to a C variable through a *converter* function.  This
+   takes two arguments: the first is a function, the second is the address of a C
+   variable (of arbitrary type), converted to :ctype:`void \*`.  The *converter*
+   function in turn is called as follows::
+
+      status = converter(object, address);
+
+   where *object* is the Python object to be converted and *address* is the
+   :ctype:`void\*` argument that was passed to the :cfunc:`PyArg_Parse\*` function.
+   The returned *status* should be ``1`` for a successful conversion and ``0`` if
+   the conversion has failed.  When the conversion fails, the *converter* function
+   should raise an exception.
+
+``S`` (string) [PyStringObject \*]
+   Like ``O`` but requires that the Python object is a string object.  Raises
+   :exc:`TypeError` if the object is not a string object.  The C variable may also
+   be declared as :ctype:`PyObject\*`.
+
+``U`` (Unicode string) [PyUnicodeObject \*]
+   Like ``O`` but requires that the Python object is a Unicode object.  Raises
+   :exc:`TypeError` if the object is not a Unicode object.  The C variable may also
+   be declared as :ctype:`PyObject\*`.
+
+``t#`` (read-only character buffer) [char \*, int]
+   Like ``s#``, but accepts any object which implements the read-only buffer
+   interface.  The :ctype:`char\*` variable is set to point to the first byte of
+   the buffer, and the :ctype:`int` is set to the length of the buffer.  Only
+   single-segment buffer objects are accepted; :exc:`TypeError` is raised for all
+   others.
+
+``w`` (read-write character buffer) [char \*]
+   Similar to ``s``, but accepts any object which implements the read-write buffer
+   interface.  The caller must determine the length of the buffer by other means,
+   or use ``w#`` instead.  Only single-segment buffer objects are accepted;
+   :exc:`TypeError` is raised for all others.
+
+``w#`` (read-write character buffer) [char \*, int]
+   Like ``s#``, but accepts any object which implements the read-write buffer
+   interface.  The :ctype:`char \*` variable is set to point to the first byte of
+   the buffer, and the :ctype:`int` is set to the length of the buffer.  Only
+   single-segment buffer objects are accepted; :exc:`TypeError` is raised for all
+   others.
+
+``(items)`` (tuple) [*matching-items*]
+   The object must be a Python sequence whose length is the number of format units
+   in *items*.  The C arguments must correspond to the individual format units in
+   *items*.  Format units for sequences may be nested.
+
+   .. note::
+
+      Prior to Python version 1.5.2, this format specifier only accepted a tuple
+      containing the individual parameters, not an arbitrary sequence.  Code which
+      previously caused :exc:`TypeError` to be raised here may now proceed without an
+      exception.  This is not expected to be a problem for existing code.
+
+It is possible to pass Python long integers where integers are requested;
+however no proper range checking is done --- the most significant bits are
+silently truncated when the receiving field is too small to receive the value
+(actually, the semantics are inherited from downcasts in C --- your mileage may
+vary).
+
+A few other characters have a meaning in a format string.  These may not occur
+inside nested parentheses.  They are:
+
+``|``
+   Indicates that the remaining arguments in the Python argument list are optional.
+   The C variables corresponding to optional arguments should be initialized to
+   their default value --- when an optional argument is not specified,
+   :cfunc:`PyArg_ParseTuple` does not touch the contents of the corresponding C
+   variable(s).
+
+``:``
+   The list of format units ends here; the string after the colon is used as the
+   function name in error messages (the "associated value" of the exception that
+   :cfunc:`PyArg_ParseTuple` raises).
+
+``;``
+   The list of format units ends here; the string after the semicolon is used as
+   the error message *instead* of the default error message.  Clearly, ``:`` and
+   ``;`` mutually exclude each other.
+
+Note that any Python object references which are provided to the caller are
+*borrowed* references; do not decrement their reference count!
+
+Additional arguments passed to these functions must be addresses of variables
+whose type is determined by the format string; these are used to store values
+from the input tuple.  There are a few cases, as described in the list of format
+units above, where these parameters are used as input values; they should match
+what is specified for the corresponding format unit in that case.
+
+For the conversion to succeed, the *arg* object must match the format and the
+format must be exhausted.  On success, the :cfunc:`PyArg_Parse\*` functions
+return true, otherwise they return false and raise an appropriate exception.
+
+
+.. cfunction:: int PyArg_ParseTuple(PyObject *args, const char *format, ...)
+
+   Parse the parameters of a function that takes only positional parameters into
+   local variables.  Returns true on success; on failure, it returns false and
+   raises the appropriate exception.
+
+
+.. cfunction:: int PyArg_VaParse(PyObject *args, const char *format, va_list vargs)
+
+   Identical to :cfunc:`PyArg_ParseTuple`, except that it accepts a va_list rather
+   than a variable number of arguments.
+
+
+.. cfunction:: int PyArg_ParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *keywords[], ...)
+
+   Parse the parameters of a function that takes both positional and keyword
+   parameters into local variables.  Returns true on success; on failure, it
+   returns false and raises the appropriate exception.
+
+
+.. cfunction:: int PyArg_VaParseTupleAndKeywords(PyObject *args, PyObject *kw, const char *format, char *keywords[], va_list vargs)
+
+   Identical to :cfunc:`PyArg_ParseTupleAndKeywords`, except that it accepts a
+   va_list rather than a variable number of arguments.
+
+
+.. cfunction:: int PyArg_Parse(PyObject *args, const char *format, ...)
+
+   Function used to deconstruct the argument lists of "old-style" functions ---
+   these are functions which use the :const:`METH_OLDARGS` parameter parsing
+   method.  This is not recommended for use in parameter parsing in new code, and
+   most code in the standard interpreter has been modified to no longer use this
+   for that purpose.  It does remain a convenient way to decompose other tuples,
+   however, and may continue to be used for that purpose.
+
+
+.. cfunction:: int PyArg_UnpackTuple(PyObject *args, const char *name, Py_ssize_t min, Py_ssize_t max, ...)
+
+   A simpler form of parameter retrieval which does not use a format string to
+   specify the types of the arguments.  Functions which use this method to retrieve
+   their parameters should be declared as :const:`METH_VARARGS` in function or
+   method tables.  The tuple containing the actual parameters should be passed as
+   *args*; it must actually be a tuple.  The length of the tuple must be at least
+   *min* and no more than *max*; *min* and *max* may be equal.  Additional
+   arguments must be passed to the function, each of which should be a pointer to a
+   :ctype:`PyObject\*` variable; these will be filled in with the values from
+   *args*; they will contain borrowed references.  The variables which correspond
+   to optional parameters not given by *args* will not be filled in; these should
+   be initialized by the caller. This function returns true on success and false if
+   *args* is not a tuple or contains the wrong number of elements; an exception
+   will be set if there was a failure.
+
+   This is an example of the use of this function, taken from the sources for the
+   :mod:`_weakref` helper module for weak references::
+
+      static PyObject *
+      weakref_ref(PyObject *self, PyObject *args)
+      {
+          PyObject *object;
+          PyObject *callback = NULL;
+          PyObject *result = NULL;
+
+          if (PyArg_UnpackTuple(args, "ref", 1, 2, &object, &callback)) {
+              result = PyWeakref_NewRef(object, callback);
+          }
+          return result;
+      }
+
+   The call to :cfunc:`PyArg_UnpackTuple` in this example is entirely equivalent to
+   this call to :cfunc:`PyArg_ParseTuple`::
+
+      PyArg_ParseTuple(args, "O|O:ref", &object, &callback)
+
+   .. versionadded:: 2.2
+
+
+.. cfunction:: PyObject* Py_BuildValue(const char *format, ...)
+
+   Create a new value based on a format string similar to those accepted by the
+   :cfunc:`PyArg_Parse\*` family of functions and a sequence of values.  Returns
+   the value or *NULL* in the case of an error; an exception will be raised if
+   *NULL* is returned.
+
+   :cfunc:`Py_BuildValue` does not always build a tuple.  It builds a tuple only if
+   its format string contains two or more format units.  If the format string is
+   empty, it returns ``None``; if it contains exactly one format unit, it returns
+   whatever object is described by that format unit.  To force it to return a tuple
+   of size 0 or one, parenthesize the format string.
+
+   When memory buffers are passed as parameters to supply data to build objects, as
+   for the ``s`` and ``s#`` formats, the required data is copied.  Buffers provided
+   by the caller are never referenced by the objects created by
+   :cfunc:`Py_BuildValue`.  In other words, if your code invokes :cfunc:`malloc`
+   and passes the allocated memory to :cfunc:`Py_BuildValue`, your code is
+   responsible for calling :cfunc:`free` for that memory once
+   :cfunc:`Py_BuildValue` returns.
+
+   In the following description, the quoted form is the format unit; the entry in
+   (round) parentheses is the Python object type that the format unit will return;
+   and the entry in [square] brackets is the type of the C value(s) to be passed.
+
+   The characters space, tab, colon and comma are ignored in format strings (but
+   not within format units such as ``s#``).  This can be used to make long format
+   strings a tad more readable.
+
+   ``s`` (string) [char \*]
+      Convert a null-terminated C string to a Python object.  If the C string pointer
+      is *NULL*, ``None`` is used.
+
+   ``s#`` (string) [char \*, int]
+      Convert a C string and its length to a Python object.  If the C string pointer
+      is *NULL*, the length is ignored and ``None`` is returned.
+
+   ``z`` (string or ``None``) [char \*]
+      Same as ``s``.
+
+   ``z#`` (string or ``None``) [char \*, int]
+      Same as ``s#``.
+
+   ``u`` (Unicode string) [Py_UNICODE \*]
+      Convert a null-terminated buffer of Unicode (UCS-2 or UCS-4) data to a Python
+      Unicode object.  If the Unicode buffer pointer is *NULL*, ``None`` is returned.
+
+   ``u#`` (Unicode string) [Py_UNICODE \*, int]
+      Convert a Unicode (UCS-2 or UCS-4) data buffer and its length to a Python
+      Unicode object.   If the Unicode buffer pointer is *NULL*, the length is ignored
+      and ``None`` is returned.
+
+   ``U`` (string) [char \*]
+      Convert a null-terminated C string to a Python unicode object. If the C string
+      pointer is *NULL*, ``None`` is used.
+
+   ``U#`` (string) [char \*, int]
+      Convert a C string and its length to a Python unicode object. If the C string
+      pointer is *NULL*, the length is ignored and ``None`` is returned.
+
+   ``i`` (integer) [int]
+      Convert a plain C :ctype:`int` to a Python integer object.
+
+   ``b`` (integer) [char]
+      Convert a plain C :ctype:`char` to a Python integer object.
+
+   ``h`` (integer) [short int]
+      Convert a plain C :ctype:`short int` to a Python integer object.
+
+   ``l`` (integer) [long int]
+      Convert a C :ctype:`long int` to a Python integer object.
+
+   ``B`` (integer) [unsigned char]
+      Convert a C :ctype:`unsigned char` to a Python integer object.
+
+   ``H`` (integer) [unsigned short int]
+      Convert a C :ctype:`unsigned short int` to a Python integer object.
+
+   ``I`` (integer/long) [unsigned int]
+      Convert a C :ctype:`unsigned int` to a Python integer object or a Python long
+      integer object, if it is larger than ``sys.maxint``.
+
+   ``k`` (integer/long) [unsigned long]
+      Convert a C :ctype:`unsigned long` to a Python integer object or a Python long
+      integer object, if it is larger than ``sys.maxint``.
+
+   ``L`` (long) [PY_LONG_LONG]
+      Convert a C :ctype:`long long` to a Python long integer object. Only available
+      on platforms that support :ctype:`long long`.
+
+   ``K`` (long) [unsigned PY_LONG_LONG]
+      Convert a C :ctype:`unsigned long long` to a Python long integer object. Only
+      available on platforms that support :ctype:`unsigned long long`.
+
+   ``n`` (int) [Py_ssize_t]
+      Convert a C :ctype:`Py_ssize_t` to a Python integer or long integer.
+
+      .. versionadded:: 2.5
+
+   ``c`` (string of length 1) [char]
+      Convert a C :ctype:`int` representing a character to a Python string of length
+      1.
+
+   ``d`` (float) [double]
+      Convert a C :ctype:`double` to a Python floating point number.
+
+   ``f`` (float) [float]
+      Same as ``d``.
+
+   ``D`` (complex) [Py_complex \*]
+      Convert a C :ctype:`Py_complex` structure to a Python complex number.
+
+   ``O`` (object) [PyObject \*]
+      Pass a Python object untouched (except for its reference count, which is
+      incremented by one).  If the object passed in is a *NULL* pointer, it is assumed
+      that this was caused because the call producing the argument found an error and
+      set an exception. Therefore, :cfunc:`Py_BuildValue` will return *NULL* but won't
+      raise an exception.  If no exception has been raised yet, :exc:`SystemError` is
+      set.
+
+   ``S`` (object) [PyObject \*]
+      Same as ``O``.
+
+   ``N`` (object) [PyObject \*]
+      Same as ``O``, except it doesn't increment the reference count on the object.
+      Useful when the object is created by a call to an object constructor in the
+      argument list.
+
+   ``O&`` (object) [*converter*, *anything*]
+      Convert *anything* to a Python object through a *converter* function.  The
+      function is called with *anything* (which should be compatible with :ctype:`void
+      \*`) as its argument and should return a "new" Python object, or *NULL* if an
+      error occurred.
+
+   ``(items)`` (tuple) [*matching-items*]
+      Convert a sequence of C values to a Python tuple with the same number of items.
+
+   ``[items]`` (list) [*matching-items*]
+      Convert a sequence of C values to a Python list with the same number of items.
+
+   ``{items}`` (dictionary) [*matching-items*]
+      Convert a sequence of C values to a Python dictionary.  Each pair of consecutive
+      C values adds one item to the dictionary, serving as key and value,
+      respectively.
+
+   If there is an error in the format string, the :exc:`SystemError` exception is
+   set and *NULL* returned.
+
+
+.. _string-conversion:
+
+String conversion and formatting
+================================
+
+Functions for number conversion and formatted string output.
+
+
+.. cfunction:: int PyOS_snprintf(char *str, size_t size,  const char *format, ...)
+
+   Output not more than *size* bytes to *str* according to the format string
+   *format* and the extra arguments. See the Unix man page :manpage:`snprintf(2)`.
+
+
+.. cfunction:: int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)
+
+   Output not more than *size* bytes to *str* according to the format string
+   *format* and the variable argument list *va*. Unix man page
+   :manpage:`vsnprintf(2)`.
+
+:cfunc:`PyOS_snprintf` and :cfunc:`PyOS_vsnprintf` wrap the Standard C library
+functions :cfunc:`snprintf` and :cfunc:`vsnprintf`. Their purpose is to
+guarantee consistent behavior in corner cases, which the Standard C functions do
+not.
+
+The wrappers ensure that *str*[*size*-1] is always ``'\0'`` upon return. They
+never write more than *size* bytes (including the trailing ``'\0'``) into str.
+Both functions require that ``str != NULL``, ``size > 0`` and ``format !=
+NULL``.
+
+If the platform doesn't have :cfunc:`vsnprintf` and the buffer size needed to
+avoid truncation exceeds *size* by more than 512 bytes, Python aborts with a
+*Py_FatalError*.
+
+The return value (*rv*) for these functions should be interpreted as follows:
+
+* When ``0 <= rv < size``, the output conversion was successful and *rv*
+  characters were written to *str* (excluding the trailing ``'\0'`` byte at
+  *str*[*rv*]).
+
+* When ``rv >= size``, the output conversion was truncated and a buffer with
+  ``rv + 1`` bytes would have been needed to succeed. *str*[*size*-1] is ``'\0'``
+  in this case.
+
+* When ``rv < 0``, "something bad happened." *str*[*size*-1] is ``'\0'`` in
+  this case too, but the rest of *str* is undefined. The exact cause of the error
+  depends on the underlying platform.
+
+The following functions provide locale-independent string to number conversions.
+
+
+.. cfunction:: double PyOS_ascii_strtod(const char *nptr, char **endptr)
+
+   Convert a string to a :ctype:`double`. This function behaves like the Standard C
+   function :cfunc:`strtod` does in the C locale. It does this without changing the
+   current locale, since that would not be thread-safe.
+
+   :cfunc:`PyOS_ascii_strtod` should typically be used for reading configuration
+   files or other non-user input that should be locale independent.
+
+   .. versionadded:: 2.4
+
+   See the Unix man page :manpage:`strtod(2)` for details.
+
+
+.. cfunction:: char * PyOS_ascii_formatd(char *buffer, size_t buf_len, const char *format, double d)
+
+   Convert a :ctype:`double` to a string using the ``'.'`` as the decimal
+   separator. *format* is a :cfunc:`printf`\ -style format string specifying the
+   number format. Allowed conversion characters are ``'e'``, ``'E'``, ``'f'``,
+   ``'F'``, ``'g'`` and ``'G'``.
+
+   The return value is a pointer to *buffer* with the converted string or NULL if
+   the conversion failed.
+
+   .. versionadded:: 2.4
+
+
+.. cfunction:: double PyOS_ascii_atof(const char *nptr)
+
+   Convert a string to a :ctype:`double` in a locale-independent way.
+
+   .. versionadded:: 2.4
+
+   See the Unix man page :manpage:`atof(2)` for details.
+