Module Objects¶

PyTypeObject PyModule_Type¶: Part of the Stable ABI.
This instance of PyTypeObject represents the Python module type. This is exposed to Python programs as types.ModuleType.

int PyModule_Check(PyObject *p)¶: Return true if p is a module object, or a subtype of a module object. This function always succeeds.

int PyModule_CheckExact(PyObject *p)¶: Return true if p is a module object, but not a subtype of PyModule_Type. This function always succeeds.

PyObject *PyModule_NewObject(PyObject *name)¶

Return value: New reference. Part of the Stable ABI since version 3.7.

Return a new module object with module.__name__ set to name. The module’s __name__, __doc__, __package__ and __loader__ attributes are filled in (all but __name__ are set to None). The caller is responsible for setting a __file__ attribute.

Return NULL with an exception set on error.

Added in version 3.3.

Changed in version 3.4: __package__ and __loader__ are now set to None.

PyObject *PyModule_New(const char *name)¶: Return value: New reference. Part of the Stable ABI.
Similar to PyModule_NewObject(), but the name is a UTF-8 encoded string instead of a Unicode object.

PyObject *PyModule_GetDict(PyObject *module)¶

Return value: Borrowed reference. Part of the Stable ABI.

Return the dictionary object that implements module’s namespace; this object is the same as the __dict__ attribute of the module object. If module is not a module object (or a subtype of a module object), SystemError is raised and NULL is returned.

It is recommended extensions use other PyModule_* and PyObject_* functions rather than directly manipulate a module’s __dict__.

PyObject *PyModule_GetNameObject(PyObject *module)¶: Return value: New reference. Part of the Stable ABI since version 3.7.
Return module’s __name__ value. If the module does not provide one, or if it is not a string, SystemError is raised and NULL is returned.

Added in version 3.3.

const char *PyModule_GetName(PyObject *module)¶: Part of the Stable ABI.
Similar to PyModule_GetNameObject() but return the name encoded to 'utf-8'.

void *PyModule_GetState(PyObject *module)¶: Part of the Stable ABI.
Return the “state” of the module, that is, a pointer to the block of memory allocated at module creation time, or NULL. See PyModuleDef.m_size.

PyModuleDef *PyModule_GetDef(PyObject *module)¶: Part of the Stable ABI.
Return a pointer to the PyModuleDef struct from which the module was created, or NULL if the module wasn’t created from a definition.

PyObject *PyModule_GetFilenameObject(PyObject *module)¶: Return value: New reference. Part of the Stable ABI.
Return the name of the file from which module was loaded using module’s __file__ attribute. If this is not defined, or if it is not a string, raise SystemError and return NULL; otherwise return a reference to a Unicode object.

Added in version 3.2.

const char *PyModule_GetFilename(PyObject *module)¶: Part of the Stable ABI.
Similar to PyModule_GetFilenameObject() but return the filename encoded to ‘utf-8’.

Deprecated since version 3.2: PyModule_GetFilename() raises UnicodeEncodeError on unencodable filenames, use PyModule_GetFilenameObject() instead.

Module definitions¶

The functions in the previous section work on any module object, including modules imported from Python code.

Modules defined using the C API typically use a module definition, PyModuleDef – a statically allocated, constant “description” of how a module should be created.

The definition is usually used to define an extension’s “main” module object (see Defining extension modules for details). It is also used to create extension modules dynamically.

Unlike PyModule_New(), the definition allows management of module state – a piece of memory that is allocated and cleared together with the module object. Unlike the module’s Python attributes, Python code cannot replace or delete data stored in module state.

type PyModuleDef¶

Part of the Stable ABI (including all members).

The module definition struct, which holds all information needed to create a module object. This structure must be statically allocated (or be otherwise guaranteed to be valid while any modules created from it exist). Usually, there is only one variable of this type for each extension module.

PyModuleDef_Base m_base¶: Always initialize this member to PyModuleDef_HEAD_INIT.

const char *m_name¶: Name for the new module.

const char *m_doc¶: Docstring for the module; usually a docstring variable created with PyDoc_STRVAR is used.

Py_ssize_t m_size¶

Module state may be kept in a per-module memory area that can be retrieved with 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 m_free function has been called, if present.

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.

Setting m_size to -1 means that the module does not support sub-interpreters, because it has global state. Negative m_size is only allowed when using legacy single-phase initialization or when creating modules dynamically.

See PEP 3121 for more details.

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

PyModuleDef_Slot *m_slots¶

An array of slot definitions for multi-phase initialization, terminated by a {0, NULL} entry. When using legacy single-phase initialization, m_slots must be NULL.

Changed in version 3.5: Prior to version 3.5, this member was always set to NULL, and was defined as:

inquiry m_reload¶

traverseproc m_traverse¶

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

This function is not called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, this function is not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

Changed in version 3.9: No longer called before the module state is allocated.

inquiry m_clear¶

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

This function is not called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, this function is not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

Like PyTypeObject.tp_clear, this function is not always called before a module is deallocated. For example, when reference counting is enough to determine that an object is no longer used, the cyclic garbage collector is not involved and m_free is called directly.

Changed in version 3.9: No longer called before the module state is allocated.

freefunc m_free¶

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

This function is not called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, this function is not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

Changed in version 3.9: No longer called before the module state is allocated.

Module slots¶

type PyModuleDef_Slot¶

int slot¶: A slot ID, chosen from the available values explained below.

void *value¶: Value of the slot, whose meaning depends on the slot ID.

Added in version 3.5.

The available slot types are:

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:

PyObject *create_module(PyObject *spec, PyModuleDef *def)¶

The function receives a 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 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 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.

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:

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.

Py_mod_multiple_interpreters¶

Specifies one of the following values:

Py_MOD_MULTIPLE_INTERPRETERS_NOT_SUPPORTED¶: The module does not support being imported in subinterpreters.

Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED¶: The module supports being imported in subinterpreters, but only when they share the main interpreter’s GIL. (See Isolating Extension Modules.)

Py_MOD_PER_INTERPRETER_GIL_SUPPORTED¶: The module supports being imported in subinterpreters, even when they have their own GIL. (See Isolating Extension Modules.)

This slot determines whether or not importing this module in a subinterpreter will fail.

Multiple Py_mod_multiple_interpreters slots may not be specified in one module definition.

If Py_mod_multiple_interpreters is not specified, the import machinery defaults to Py_MOD_MULTIPLE_INTERPRETERS_SUPPORTED.

Added in version 3.12.

Py_mod_gil¶

Specifies one of the following values:

Py_MOD_GIL_USED¶: The module depends on the presence of the global interpreter lock (GIL), and may access global state without synchronization.

Py_MOD_GIL_NOT_USED¶: The module is safe to run without an active GIL.

This slot is ignored by Python builds not configured with --disable-gil. Otherwise, it determines whether or not importing this module will cause the GIL to be automatically enabled. See Free-threaded CPython for more detail.

Multiple Py_mod_gil slots may not be specified in one module definition.

If Py_mod_gil is not specified, the import machinery defaults to Py_MOD_GIL_USED.

Added in version 3.13.

Creating extension modules dynamically¶

The following functions may be used to create a module outside of an extension’s initialization function. They are also used in single-phase initialization.

PyObject *PyModule_Create(PyModuleDef *def)¶: Return value: New reference.
Create a new module object, given the definition in def. This is a macro that calls PyModule_Create2() with module_api_version set to PYTHON_API_VERSION, or to PYTHON_ABI_VERSION if using the limited API.

PyObject *PyModule_Create2(PyModuleDef *def, int module_api_version)¶

Return value: New reference. Part of the Stable ABI.

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 RuntimeWarning is emitted.

Return NULL with an exception set on error.

This function does not support slots. The m_slots member of def must be NULL.

Note

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

PyObject *PyModule_FromDefAndSpec(PyModuleDef *def, PyObject *spec)¶: Return value: New reference.
This macro calls PyModule_FromDefAndSpec2() with module_api_version set to PYTHON_API_VERSION, or to PYTHON_ABI_VERSION if using the limited API.

Added in version 3.5.

PyObject *PyModule_FromDefAndSpec2(PyModuleDef *def, PyObject *spec, int module_api_version)¶

Return value: New reference. Part of the Stable ABI since version 3.7.

Create a new module object, given the definition in def and the ModuleSpec spec, assuming the API version module_api_version. If that version does not match the version of the running interpreter, a RuntimeWarning is emitted.

Return NULL with an exception set on error.

Note that this does not process execution slots (Py_mod_exec). Both PyModule_FromDefAndSpec and PyModule_ExecDef must be called to fully initialize a module.

Note

Most uses of this function should be using PyModule_FromDefAndSpec() instead; only use this if you are sure you need it.

Added in version 3.5.

int PyModule_ExecDef(PyObject *module, PyModuleDef *def)¶: Part of the Stable ABI since version 3.7.
Process any execution slots (Py_mod_exec) given in def.

Added in version 3.5.

PYTHON_API_VERSION¶

The C API version. Defined for backwards compatibility.

Currently, this constant is not updated in new Python versions, and is not useful for versioning. This may change in the future.

PYTHON_ABI_VERSION¶

Defined as 3 for backwards compatibility.

Currently, this constant is not updated in new Python versions, and is not useful for versioning. This may change in the future.

Support functions¶

The following functions are provided to help initialize a module state. They are intended for a module’s execution slots (Py_mod_exec), the initialization function for legacy single-phase initialization, or code that creates modules dynamically.

int PyModule_AddObjectRef(PyObject *module, const char *name, PyObject *value)¶

Part of the Stable ABI since version 3.10.

Add an object to module as name. This is a convenience function which can be used from the module’s initialization function.

On success, return 0. On error, raise an exception and return -1.

Example usage:

static int
add_spam(PyObject *module, int value)
{
    PyObject *obj = PyLong_FromLong(value);
    if (obj == NULL) {
        return -1;
    }
    int res = PyModule_AddObjectRef(module, "spam", obj);
    Py_DECREF(obj);
    return res;
 }

To be convenient, the function accepts NULL value with an exception set. In this case, return -1 and just leave the raised exception unchanged.

The example can also be written without checking explicitly if obj is NULL:

static int
add_spam(PyObject *module, int value)
{
    PyObject *obj = PyLong_FromLong(value);
    int res = PyModule_AddObjectRef(module, "spam", obj);
    Py_XDECREF(obj);
    return res;
 }

Note that Py_XDECREF() should be used instead of Py_DECREF() in this case, since obj can be NULL.

The number of different name strings passed to this function should be kept small, usually by only using statically allocated strings as name. For names that aren’t known at compile time, prefer calling PyUnicode_FromString() and PyObject_SetAttr() directly. For more details, see PyUnicode_InternFromString(), which may be used internally to create a key object.

Added in version 3.10.

int PyModule_Add(PyObject *module, const char *name, PyObject *value)¶

Part of the Stable ABI since version 3.13.

Similar to PyModule_AddObjectRef(), but “steals” a reference to value. It can be called with a result of function that returns a new reference without bothering to check its result or even saving it to a variable.

Example usage:

if (PyModule_Add(module, "spam", PyBytes_FromString(value)) < 0) {
    goto error;
}

Added in version 3.13.

int PyModule_AddObject(PyObject *module, const char *name, PyObject *value)¶

Part of the Stable ABI.

Similar to PyModule_AddObjectRef(), but steals a reference to value on success (if it returns 0).

The new PyModule_Add() or PyModule_AddObjectRef() functions are recommended, since it is easy to introduce reference leaks by misusing the PyModule_AddObject() function.

Note

Unlike other functions that steal references, PyModule_AddObject() only releases the reference to value on success.

This means that its return value must be checked, and calling code must Py_XDECREF() value manually on error.

Example usage:

PyObject *obj = PyBytes_FromString(value);
if (PyModule_AddObject(module, "spam", obj) < 0) {
    // If 'obj' is not NULL and PyModule_AddObject() failed,
    // 'obj' strong reference must be deleted with Py_XDECREF().
    // If 'obj' is NULL, Py_XDECREF() does nothing.
    Py_XDECREF(obj);
    goto error;
}
// PyModule_AddObject() stole a reference to obj:
// Py_XDECREF(obj) is not needed here.

Deprecated since version 3.13: PyModule_AddObject() is soft deprecated.

int PyModule_AddIntConstant(PyObject *module, const char *name, long value)¶

Part of the Stable ABI.

Add an integer constant to module as name. This convenience function can be used from the module’s initialization function. Return -1 with an exception set on error, 0 on success.

This is a convenience function that calls PyLong_FromLong() and PyModule_AddObjectRef(); see their documentation for details.

int PyModule_AddStringConstant(PyObject *module, const char *name, const char *value)¶

Part of the Stable ABI.

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 with an exception set on error, 0 on success.

This is a convenience function that calls PyUnicode_InternFromString() and PyModule_AddObjectRef(); see their documentation for details.

PyModule_AddIntMacro(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 with an exception set on error, 0 on success.

PyModule_AddStringMacro(module, macro)¶: Add a string constant to module.

int PyModule_AddType(PyObject *module, PyTypeObject *type)¶: Part of the Stable ABI since version 3.10.
Add a type object to module. The type object is finalized by calling internally PyType_Ready(). The name of the type object is taken from the last component of tp_name after dot. Return -1 with an exception set on error, 0 on success.

Added in version 3.9.

int PyModule_AddFunctions(PyObject *module, PyMethodDef *functions)¶

Part of the Stable ABI since version 3.7.

Add the functions from the NULL terminated functions array to module. Refer to the 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 (such as when using Multi-phase initialization, PyModule_Create, or PyModule_FromDefAndSpec). Some module authors may prefer defining functions in multiple PyMethodDef arrays; in that case they should call this function directly.

Added in version 3.5.

int PyModule_SetDocString(PyObject *module, const char *docstring)¶: Part of the Stable ABI since version 3.7.
Set the docstring for module to docstring. This function is called automatically when creating a module from PyModuleDef (such as when using Multi-phase initialization, PyModule_Create, or PyModule_FromDefAndSpec).

Added in version 3.5.

int PyUnstable_Module_SetGIL(PyObject *module, void *gil)¶: This is Unstable API. It may change without warning in minor releases.

Indicate that module does or does not support running without the global interpreter lock (GIL), using one of the values from Py_mod_gil. It must be called during module’s initialization function when using Legacy single-phase initialization. If this function is not called during module initialization, the import machinery assumes the module does not support running without the GIL. This function is only available in Python builds configured with --disable-gil. Return -1 with an exception set on error, 0 on success.

Added in version 3.13.

Module lookup (single-phase initialization)¶

The legacy single-phase initialization initialization scheme 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.

PyObject *PyState_FindModule(PyModuleDef *def)¶: Return value: Borrowed reference. Part of the Stable ABI.
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 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.

int PyState_AddModule(PyObject *module, PyModuleDef *def)¶

Part of the Stable ABI since version 3.3.

Attaches the module object passed to the function to the interpreter state. This allows the module object to be accessible via PyState_FindModule().

Only effective on modules created using single-phase initialization.

Python calls PyState_AddModule automatically after importing a module that uses single-phase initialization, so it is unnecessary (but harmless) to call it from module initialization code. An explicit call is needed only if the module’s own init code subsequently calls PyState_FindModule. The function is mainly intended for implementing alternative import mechanisms (either by calling it directly, or by referring to its implementation for details of the required state updates).

If a module was attached previously using the same def, it is replaced by the new module.

The caller must have an attached thread state.

Return -1 with an exception set on error, 0 on success.

Added in version 3.3.

int PyState_RemoveModule(PyModuleDef *def)¶

Part of the Stable ABI since version 3.3.

Removes the module object created from def from the interpreter state. Return -1 with an exception set on error, 0 on success.

The caller must have an attached thread state.

Added in version 3.3.

Module Objects¶

Module definitions¶

Module slots¶

Creating extension modules dynamically¶

Support functions¶

Module lookup (single-phase initialization)¶

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