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