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__".

   The returned reference is borrowed from the module; it is valid
   until the module is destroyed.

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'".

   The returned buffer is only valid until the module is renamed or
   destroyed. Note that Python code may rename a module by setting its
   "__name__" attribute.

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.

   On error, return "NULL" with an exception set. Use
   "PyErr_Occurred()" to tell this case apart from a missing
   "PyModuleDef".

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'.

   The returned buffer is only valid until the module's "__file__"
   attribute is reassigned or the module is destroyed.

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


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
"PyImport_AppendInittab()"). See Building C and C++ Extensions or
Extending Embedded Python for details.

The initialization function can either pass a module definition
instance to "PyModule_Create()", and return the resulting module
object, or request "multi-phase initialization" by returning the
definition struct itself.

type PyModuleDef
    * Part of the Stable ABI (including all members).*

   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.

   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 "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.

   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 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.


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:

PyObject *PyModule_Create(PyModuleDef *def)
    *Return value: New reference.*

   Create a new module object, given the definition in *def*.  This
   behaves like "PyModule_Create2()" with *module_api_version* set to
   "PYTHON_API_VERSION".

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.

   Note:

     Most uses of this function should be using "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
"PyModule_AddObjectRef()".


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 "__new__()"
and "__init__()" methods of classes.

Unlike modules created using single-phase initialization, these
modules are not singletons. For example, if the "sys.modules" entry is
removed and the module is re-imported, a new module object is created,
and typically populated with fresh method and type objects. The old
module is subject to normal garbage collection. This mirrors the
behavior of pure-Python modules.

Additional module instances may be created in sub-interpreters or
after after Python runtime reinitialization ("Py_Finalize()" and
"Py_Initialize()"). In these cases, sharing Python objects between
module instances would likely cause crashes or undefined behavior.

To avoid such issues, each instance of an extension module should be
*isolated*: changes to one instance should not implicitly affect the
others, and all state, including references to Python objects, should
be specific to a particular module instance. See Isolating Extension
Modules for more details and a practical guide.

A simpler way to avoid these issues is raising an error on repeated
initialization.

All modules created using multi-phase initialization are expected to
support sub-interpreters, or otherwise explicitly signal a lack of
support. This is usually achieved by isolation or blocking repeated
initialization, as above. A module may also be limited to the main
interpreter using the "Py_mod_multiple_interpreters" slot.

To request multi-phase initialization, the initialization function
(PyInit_modulename) returns a "PyModuleDef" instance with non-empty
"m_slots". Before it is returned, the "PyModuleDef" instance must be
initialized with the following function:

PyObject *PyModuleDef_Init(PyModuleDef *def)
    *Return value: Borrowed reference.** Part of the Stable ABI since
   version 3.5.*

   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.

   Added in version 3.5.

The *m_slots* member of the module definition must point to an array
of "PyModuleDef_Slot" structures:

type PyModuleDef_Slot
    * Part of the Stable ABI (including all members) since version
   3.5.*

   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 *m_slots* array must be terminated by a slot with id 0.

The available slot types are:

Py_mod_create
    * Part of the Stable ABI since version 3.5.*

   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".

   Added in version 3.5.

Py_mod_exec
    * Part of the Stable ABI since version 3.5.*

   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.

   Added in version 3.5.

Py_mod_multiple_interpreters
    * Part of the Stable ABI since version 3.12.*

   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
    * Part of the Stable ABI since version 3.13.*

   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.

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.

PyObject *PyModule_FromDefAndSpec(PyModuleDef *def, PyObject *spec)
    *Return value: New reference.*

   Create a new module object, given the definition in *def* and the
   ModuleSpec *spec*.  This behaves like "PyModule_FromDefAndSpec2()"
   with *module_api_version* set to "PYTHON_API_VERSION".

   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:

     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.

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",
   using either "PyModule_Create" or "PyModule_FromDefAndSpec".

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

   Added in version 3.5.

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", using either
   "PyModule_Create" or "PyModule_FromDefAndSpec".

   The *functions* array must be statically allocated (or otherwise
   guaranteed to outlive the module object).

   Added in version 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:

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 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. 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 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, 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).

   The caller must hold the GIL.

   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 hold the GIL.

   Added in version 3.3.
