/usr/share/doc/python3-docs/html/_sources/c-api
Edit: /usr/share/doc/python3-docs/html/_sources/c-api/module.rst.txt (18266B)
.. 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:`PyModule_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:`~object.__dict__` attribute of the module object.
If *module* is not a module object (or a subtype of a module object),
:exc:`SystemError` is raised and *NULL* is returned.
It is recommended extensions use other :c:func:`PyModule_\*` and
:c:func:`PyObject_\*` functions rather than directly manipulate a module's
:attr:`~object.__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. This function may be called before module state
is allocated (:c:func:`PyModule_GetState()` may return `NULL`),
and before the :c:member:`Py_mod_exec` function is executed.
.. c:member:: inquiry m_clear
A clear function to call during GC clearing of the module object, or
*NULL* if not needed. This function may be called before module state
is allocated (:c:func:`PyModule_GetState()` may return `NULL`),
and before the :c:member:`Py_mod_exec` function is executed.
.. c:member:: freefunc m_free
A function to call during deallocation of the module object, or *NULL* if
not needed. This function may be called before module state
is allocated (:c:func:`PyModule_GetState()` may return `NULL`),
and before the :c:member:`Py_mod_exec` function is executed.
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_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