cpython/Doc/c-api/module.rst

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.. 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 an 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:: 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.
Per-interpreter module state
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Single-phase initialization creates singleton modules that can store additional
information as part of the interpreter, allow that state to be retrieved later
with only a reference to the module definition, rather than to the module
itself.
.. 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 with
:c:func:`PyModule_Create`.
.. 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`.
.. versionadded:: 3.3
.. c:function:: int PyState_RemoveModule(PyModuleDef *def)
Removes the module object created from *def* from the interpreter state.
.. versionadded:: 3.3
Initializing C modules
^^^^^^^^^^^^^^^^^^^^^^
.. c:type:: 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 :c:func:`PyModule_Create` in the
module initialization function.
.. 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
Some modules allow re-initialization (calling their ``PyInit_*`` function
more than once). These modules should keep their state in a per-module
memory area that can be retrieved with :c:func:`PyModule_GetState`.
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 :c:member:`m_free`
function has been called, if present.
Setting ``m_size`` to ``-1`` means that the module can not be
re-initialized 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.
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 *NULL* entry.
.. 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.
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 *module)
Create a new module object, given the definition in *module*. This behaves
like :c:func:`PyModule_Create2` with *module_api_version* set to
:const:`PYTHON_API_VERSION`.
.. c:function:: 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 :c:func:`PyModule_Create`
instead; only use this if you are sure you need it.
Alternatively, the module initialization function may instead return a
:c:type:`PyModuleDef` instance with a non-empty ``m_slots`` array. This is
referred to as "multi-phase initialization", and ``PyModuleDef`` instance
should be initialized with the following function:
.. c:function:: PyObject* PyModuleDef_Init(PyModuleDef *module)
Ensures a module definition is a properly initialized Python object that
correctly reports its type and reference count.
.. XXX (ncoghlan): It's not clear if it makes sense to document PyModule_ExecDef
PyModule_FromDefAndSpec or PyModule_FromDefAndSpec2 here, as end user code
generally shouldn't be calling those.
The module initialization function (if using single phase initialization) or
a function called from a module execution slot (if using multiphase
initialization), can use the following functions to help initialize the module
state:
.. c:function:: int PyModule_SetDocString(PyObject *module, const char *docstring)
Set the docstring for *module* to *docstring*. Return ``-1`` on error, ``0``
on success.
.. 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).
.. 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*.