Doc/c-api/module.rst

.. highlightlang:: c

.. _moduleobjects:

Module Objects
--------------

.. index:: object: module

There are only a few functions special to module objects.


.. cvar:: PyTypeObject PyModule_Type

   .. index:: single: ModuleType (in module types)

   This instance of :ctype:`PyTypeObject` represents the Python module type.  This
   is exposed to Python programs as ``types.ModuleType``.


.. cfunction:: int PyModule_Check(PyObject *p)

   Return true if *p* is a module object, or a subtype of a module object.


.. cfunction:: int PyModule_CheckExact(PyObject *p)

   Return true if *p* is a module object, but not a subtype of
   :cdata:`PyModule_Type`.


.. cfunction:: PyObject* PyModule_New(const char *name)

   .. index::
      single: __name__ (module attribute)
      single: __doc__ (module attribute)
      single: __file__ (module attribute)

   Return a new module object with the :attr:`__name__` attribute set to *name*.
   Only the module's :attr:`__doc__` and :attr:`__name__` attributes are filled in;
   the caller is responsible for providing a :attr:`__file__` attribute.


.. cfunction:: PyObject* PyModule_GetDict(PyObject *module)

   .. index:: single: __dict__ (module attribute)

   Return the dictionary object that implements *module*'s namespace; this object
   is the same as the :attr:`__dict__` attribute of the module object.  This
   function never fails.  It is recommended extensions use other
   :cfunc:`PyModule_\*` and :cfunc:`PyObject_\*` functions rather than directly
   manipulate a module's :attr:`__dict__`.


.. cfunction:: char* PyModule_GetName(PyObject *module)

   .. index::
      single: __name__ (module attribute)
      single: SystemError (built-in exception)

   Return *module*'s :attr:`__name__` value.  If the module does not provide one,
   or if it is not a string, :exc:`SystemError` is raised and *NULL* is returned.


.. cfunction:: char* PyModule_GetFilename(PyObject *module)

   .. index::
      single: __file__ (module attribute)
      single: SystemError (built-in exception)

   Return the name of the file from which *module* was loaded using *module*'s
   :attr:`__file__` attribute.  If this is not defined, or if it is not a string,
   raise :exc:`SystemError` and return *NULL*.


.. cfunction:: void* PyModule_GetState(PyObject *module)

   Return the "state" of the module, that is, a pointer to the block of memory
   allocated at module creation time, or *NULL*.  See
   :cmember:`PyModuleDef.m_size`.


.. cfunction:: PyModuleDef* PyModule_GetDef(PyObject *module)

   Return a pointer to the :ctype:`PyModuleDef` struct from which the module was
   created, or *NULL* if the module wasn't created with
   :cfunc:`PyModule_Create`.


Initializing C modules
^^^^^^^^^^^^^^^^^^^^^^

These functions are usually used in the module initialization function.

.. cfunction:: PyObject* PyModule_Create(PyModuleDef *module)

   Create a new module object, given the definition in *module*.  This behaves
   like :cfunc:`PyModule_Create2` with *module_api_version* set to
   :const:`PYTHON_API_VERSION`.


.. cfunction:: PyObject* PyModule_Create2(PyModuleDef *module, int module_api_version)

   Create a new module object, given the definition in *module*, assuming the
   API version *module_api_version*.  If that version does not match the version
   of the running interpreter, a :exc:`RuntimeWarning` is emitted.

   .. note::

      Most uses of this function should be using :cfunc:`PyModule_Create`
      instead; only use this if you are sure you need it.


.. ctype:: PyModuleDef

   This struct holds all information that is needed to create a module object.
   There is usually only one static variable of that type for each module, which
   is statically initialized and then passed to :cfunc:`PyModule_Create` in the
   module initialization function.

   .. cmember:: PyModuleDef_Base m_base

      Always initialize this member to :const:`PyModuleDef_HEAD_INIT`.

   .. cmember:: char* m_name

      Name for the new module.

   .. cmember:: char* m_doc

      Docstring for the module; usually a docstring variable created with
      :cfunc:`PyDoc_STRVAR` is used.

   .. cmember:: Py_ssize_t m_size

      If the module object needs additional memory, this should be set to the
      number of bytes to allocate; a pointer to the block of memory can be
      retrieved with :cfunc:`PyModule_GetState`.  If no memory is needed, set
      this to ``-1``.

      This memory should be used, rather than static globals, to hold per-module
      state, since it is then safe for use in multiple sub-interpreters.  It is
      freed when the module object is deallocated, after the :cmember:`m_free`
      function has been called, if present.

   .. cmember:: PyMethodDef* m_methods

      A pointer to a table of module-level functions, described by
      :ctype:`PyMethodDef` values.  Can be *NULL* if no functions are present.

   .. cmember:: inquiry m_reload

      Currently unused, should be *NULL*.

   .. cmember:: traverseproc m_traverse

      A traversal function to call during GC traversal of the module object, or
      *NULL* if not needed.

   .. cmember:: inquiry m_clear

      A clear function to call during GC clearing of the module object, or
      *NULL* if not needed.

   .. cmember:: freefunc m_free

      A function to call during deallocation of the module object, or *NULL* if
      not needed.


.. cfunction:: int PyModule_AddObject(PyObject *module, const char *name, PyObject *value)

   Add an object to *module* as *name*.  This is a convenience function which can
   be used from the module's initialization function.  This steals a reference to
   *value*.  Return ``-1`` on error, ``0`` on success.


.. cfunction:: int PyModule_AddIntConstant(PyObject *module, const char *name, long value)

   Add an integer constant to *module* as *name*.  This convenience function can be
   used from the module's initialization function. Return ``-1`` on error, ``0`` on
   success.


.. cfunction:: int PyModule_AddStringConstant(PyObject *module, const char *name, const char *value)

   Add a string constant to *module* as *name*.  This convenience function can be
   used from the module's initialization function.  The string *value* must be
   null-terminated.  Return ``-1`` on error, ``0`` on success.


.. cfunction:: int PyModule_AddIntMacro(PyObject *module, macro)

   Add an int constant to *module*. The name and the value are taken from
   *macro*. For example ``PyModule_AddConstant(module, AF_INET)`` adds the int
   constant *AF_INET* with the value of *AF_INET* to *module*.
   Return ``-1`` on error, ``0`` on success.


.. cfunction:: int PyModule_AddStringMacro(PyObject *module, macro)

   Add a string constant to *module*.