.. highlightlang:: c .. _moduleobjects: Module Objects -------------- .. index:: object: module .. c:var:: PyTypeObject PyModule_Type .. index:: single: ModuleType (in module types) This instance of :c:type:`PyTypeObject` represents the Python module type. This is exposed to Python programs as ``types.ModuleType``. .. c:function:: int PyModule_Check(PyObject *p) Return true if *p* is a module object, or a subtype of a module object. .. c:function:: int PyModule_CheckExact(PyObject *p) Return true if *p* is a module object, but not a subtype of :c:data:`PyModule_Type`. .. c:function:: PyObject* PyModule_NewObject(PyObject *name) .. index:: single: __name__ (module attribute) single: __doc__ (module attribute) single: __file__ (module attribute) single: __package__ (module attribute) single: __loader__ (module attribute) Return a new module object with the :attr:`__name__` attribute set to *name*. The module's :attr:`__name__`, :attr:`__doc__`, :attr:`__package__`, and :attr:`__loader__` attributes are filled in (all but :attr:`__name__` are set to ``None``); the caller is responsible for providing a :attr:`__file__` attribute. .. versionadded:: 3.3 .. versionchanged:: 3.4 :attr:`__package__` and :attr:`__loader__` are set to ``None``. .. c:function:: PyObject* PyModule_New(const char *name) Similar to :c:func:`PyImport_NewObject`, but the name is a UTF-8 encoded string instead of a Unicode object. .. c:function:: 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 :c:func:`PyModule_\*` and :c:func:`PyObject_\*` functions rather than directly manipulate a module's :attr:`__dict__`. .. c:function:: PyObject* PyModule_GetNameObject(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. .. versionadded:: 3.3 .. c:function:: char* PyModule_GetName(PyObject *module) Similar to :c:func:`PyModule_GetNameObject` but return the name encoded to ``'utf-8'``. .. c:function:: 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 :c:member:`PyModuleDef.m_size`. .. c:function:: PyModuleDef* PyModule_GetDef(PyObject *module) Return a pointer to the :c:type:`PyModuleDef` struct from which the module was created, or *NULL* if the module wasn't created from a definition. .. c:function:: PyObject* PyModule_GetFilenameObject(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 unicode string, raise :exc:`SystemError` and return *NULL*; otherwise return a reference to a Unicode object. .. versionadded:: 3.2 .. c:function:: char* PyModule_GetFilename(PyObject *module) Similar to :c:func:`PyModule_GetFilenameObject` but return the filename encoded to 'utf-8'. .. deprecated:: 3.2 :c:func:`PyModule_GetFilename` raises :c:type:`UnicodeEncodeError` on unencodable filenames, use :c:func:`PyModule_GetFilenameObject` instead. .. _initializing-modules: Initializing C modules ^^^^^^^^^^^^^^^^^^^^^^ Modules objects are usually created from extension modules (shared libraries which export an initialization function), or compiled-in modules (where the initialization function is added using :c:func:`PyImport_AppendInittab`). See :ref:`building` or :ref:`extending-with-embedding` for details. The initialization function can either pass a module definition instance to :c:func:`PyModule_Create`, and return the resulting module object, or request "multi-phase initialization" by returning the definition struct itself. .. c:type:: PyModuleDef The module definition struct, which holds all information needed to create a module object. There is usually only one statically initialized variable of this type for each module. .. c:member:: PyModuleDef_Base m_base Always initialize this member to :const:`PyModuleDef_HEAD_INIT`. .. c:member:: char* m_name Name for the new module. .. c:member:: char* m_doc Docstring for the module; usually a docstring variable created with :c:func:`PyDoc_STRVAR` is used. .. c:member:: Py_ssize_t m_size Module state may be kept in a per-module memory area that can be retrieved with :c:func:`PyModule_GetState`, rather than in static globals. This makes modules safe for use in multiple sub-interpreters. This memory area is allocated based on *m_size* on module creation, and freed when the module object is deallocated, after the :c:member:`m_free` function has been called, if present. Setting ``m_size`` to ``-1`` means that the module does not support sub-interpreters, because it has global state. Setting it to a non-negative value means that the module can be re-initialized and specifies the additional amount of memory it requires for its state. Non-negative ``m_size`` is required for multi-phase initialization. See :PEP:`3121` for more details. .. c:member:: PyMethodDef* m_methods A pointer to a table of module-level functions, described by :c:type:`PyMethodDef` values. Can be *NULL* if no functions are present. .. c:member:: PyModuleDef_Slot* m_slots An array of slot definitions for multi-phase initialization, terminated by a ``{0, NULL}`` entry. When using single-phase initialization, *m_slots* must be *NULL*. .. versionchanged:: 3.5 Prior to version 3.5, this member was always set to *NULL*, and was defined as: .. c:member:: inquiry m_reload .. c:member:: traverseproc m_traverse A traversal function to call during GC traversal of the module object, or *NULL* if not needed. .. c:member:: inquiry m_clear A clear function to call during GC clearing of the module object, or *NULL* if not needed. .. c:member:: freefunc m_free A function to call during deallocation of the module object, or *NULL* if not needed. Single-phase initialization ........................... The module initialization function may create and return the module object directly. This is referred to as "single-phase initialization", and uses one of the following two module creation functions: .. c:function:: PyObject* PyModule_Create(PyModuleDef *def) Create a new module object, given the definition in *def*. This behaves like :c:func:`PyModule_Create2` with *module_api_version* set to :const:`PYTHON_API_VERSION`. .. c:function:: PyObject* PyModule_Create2(PyModuleDef *def, int module_api_version) Create a new module object, given the definition in *def*, 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 :c:func:`PyModule_Create` instead; only use this if you are sure you need it. Before it is returned from in the initialization function, the resulting module object is typically populated using functions like :c:func:`PyModule_AddObject`. .. _multi-phase-initialization: Multi-phase initialization .......................... An alternate way to specify extensions is to request "multi-phase initialization". Extension modules created this way behave more like Python modules: the initialization is split between the *creation phase*, when the module object is created, and the *execution phase*, when it is populated. The distinction is similar to the :py:meth:`__new__` and :py:meth:`__init__` methods of classes. Unlike modules created using single-phase initialization, these modules are not singletons: if the *sys.modules* entry is removed and the module is re-imported, a new module object is created, and the old module is subject to normal garbage collection -- as with Python modules. By default, multiple modules created from the same definition should be independent: changes to one should not affect the others. This means that all state should be specific to the module object (using e.g. using :c:func:`PyModule_GetState`), or its contents (such as the module's :attr:`__dict__` or individual classes created with :c:func:`PyType_FromSpec`). All modules created using multi-phase initialization are expected to support :ref:`sub-interpreters `. Making sure multiple modules are independent is typically enough to achieve this. To request multi-phase initialization, the initialization function (PyInit_modulename) returns a :c:type:`PyModuleDef` instance with non-empty :c:member:`~PyModuleDef.m_slots`. Before it is returned, the ``PyModuleDef`` instance must be initialized with the following function: .. c:function:: PyObject* PyModuleDef_Init(PyModuleDef *def) Ensures a module definition is a properly initialized Python object that correctly reports its type and reference count. Returns *def* cast to ``PyObject*``, or *NULL* if an error occurred. .. versionadded:: 3.5 The *m_slots* member of the module definition must point to an array of ``PyModuleDef_Slot`` structures: .. c:type:: PyModuleDef_Slot .. c:member:: int slot A slot ID, chosen from the available values explained below. .. c:member:: void* value Value of the slot, whose meaning depends on the slot ID. .. versionadded:: 3.5 The *m_slots* array must be terminated by a slot with id 0. The available slot types are: .. c:var:: Py_mod_create Specifies a function that is called to create the module object itself. The *value* pointer of this slot must point to a function of the signature: .. c:function:: PyObject* create_module(PyObject *spec, PyModuleDef *def) The function receives a :py:class:`~importlib.machinery.ModuleSpec` instance, as defined in :PEP:`451`, and the module definition. It should return a new module object, or set an error and return *NULL*. This function should be kept minimal. In particular, it should not call arbitrary Python code, as trying to import the same module again may result in an infinite loop. Multiple ``Py_mod_create`` slots may not be specified in one module definition. If ``Py_mod_create`` is not specified, the import machinery will create a normal module object using :c:func:`PyModule_New`. The name is taken from *spec*, not the definition, to allow extension modules to dynamically adjust to their place in the module hierarchy and be imported under different names through symlinks, all while sharing a single module definition. There is no requirement for the returned object to be an instance of :c:type:`PyModule_Type`. Any type can be used, as long as it supports setting and getting import-related attributes. However, only ``PyModule_Type`` instances may be returned if the ``PyModuleDef`` has non-*NULL* ``m_methods``, ``m_traverse``, ``m_clear``, ``m_free``; non-zero ``m_size``; or slots other than ``Py_mod_create``. .. c:var:: Py_mod_exec Specifies a function that is called to *execute* the module. This is equivalent to executing the code of a Python module: typically, this function adds classes and constants to the module. The signature of the function is: .. c:function:: int exec_module(PyObject* module) If multiple ``Py_mod_exec`` slots are specified, they are processed in the order they appear in the *m_slots* array. See :PEP:`489` for more details on multi-phase initialization. Low-level module creation functions ................................... The following functions are called under the hood when using multi-phase initialization. They can be used directly, for example when creating module objects dynamically. Note that both ``PyModule_FromDefAndSpec`` and ``PyModule_ExecDef`` must be called to fully initialize a module. .. c:function:: PyObject * PyModule_FromDefAndSpec(PyModuleDef *def, PyObject *spec) Create a new module object, given the definition in *module* and the ModuleSpec *spec*. This behaves like :c:func:`PyModule_FromDefAndSpec2` with *module_api_version* set to :const:`PYTHON_API_VERSION`. .. versionadded:: 3.5 .. c:function:: PyObject * PyModule_FromDefAndSpec2(PyModuleDef *def, PyObject *spec, int module_api_version) Create a new module object, given the definition in *module* and the ModuleSpec *spec*, 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 :c:func:`PyModule_FromDefAndSpec` instead; only use this if you are sure you need it. .. versionadded:: 3.5 .. c:function:: int PyModule_ExecDef(PyObject *module, PyModuleDef *def) Process any execution slots (:c:data:`Py_mod_exec`) given in *def*. .. versionadded:: 3.5 .. c:function:: int PyModule_SetDocString(PyObject *module, const char *docstring) Set the docstring for *module* to *docstring*. This function is called automatically when creating a module from ``PyModuleDef``, using either ``PyModule_Create`` or ``PyModule_FromDefAndSpec``. .. versionadded:: 3.5 .. c:function:: int PyModule_AddFunctions(PyObject *module, PyMethodDef *functions) Add the functions from the *NULL* terminated *functions* array to *module*. Refer to the :c:type:`PyMethodDef` documentation for details on individual entries (due to the lack of a shared module namespace, module level "functions" implemented in C typically receive the module as their first parameter, making them similar to instance methods on Python classes). This function is called automatically when creating a module from ``PyModuleDef``, using either ``PyModule_Create`` or ``PyModule_FromDefAndSpec``. .. versionadded:: 3.5 Support functions ................. The module initialization function (if using single phase initialization) or a function called from a module execution slot (if using multi-phase initialization), can use the following functions to help initialize the module state: .. c:function:: 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. .. c:function:: 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. .. c:function:: 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. .. c:function:: int PyModule_AddIntMacro(PyObject *module, macro) Add an int constant to *module*. The name and the value are taken from *macro*. For example ``PyModule_AddIntMacro(module, AF_INET)`` adds the int constant *AF_INET* with the value of *AF_INET* to *module*. Return ``-1`` on error, ``0`` on success. .. c:function:: int PyModule_AddStringMacro(PyObject *module, macro) Add a string constant to *module*. Module lookup ^^^^^^^^^^^^^ Single-phase initialization creates singleton modules that can be looked up in the context of the current interpreter. This allows the module object to be retrieved later with only a reference to the module definition. These functions will not work on modules created using multi-phase initialization, since multiple such modules can be created from a single definition. .. c:function:: PyObject* PyState_FindModule(PyModuleDef *def) Returns the module object that was created from *def* for the current interpreter. This method requires that the module object has been attached to the interpreter state with :c:func:`PyState_AddModule` beforehand. In case the corresponding module object is not found or has not been attached to the interpreter state yet, it returns *NULL*. .. c:function:: int PyState_AddModule(PyObject *module, PyModuleDef *def) Attaches the module object passed to the function to the interpreter state. This allows the module object to be accessible via :c:func:`PyState_FindModule`. Only effective on modules created using single-phase initialization. .. versionadded:: 3.3 .. c:function:: int PyState_RemoveModule(PyModuleDef *def) Removes the module object created from *def* from the interpreter state. .. versionadded:: 3.3