.. highlightlang:: c

.. _importing:

Importing Modules

.. c:function:: PyObject* PyImport_ImportModule(const char *name)

.. index:: single: package variable; all single: all (package variable) single: modules (in module sys)

This is a simplified interface to :c:func:PyImport_ImportModuleEx below, leaving the globals and locals arguments set to NULL and level set to 0. When the name argument contains a dot (when it specifies a submodule of a package), the fromlist argument is set to the list ['*'] so that the return value is the named module rather than the top-level package containing it as would otherwise be the case. (Unfortunately, this has an additional side effect when name in fact specifies a subpackage instead of a submodule: the submodules specified in the package's __all__ variable are loaded.) Return a new reference to the imported module, or NULL with an exception set on failure. A failing import of a module doesn't leave the module in :data:sys.modules.

This function always uses absolute imports.

.. c:function:: PyObject* PyImport_ImportModuleNoBlock(const char *name)

This function is a deprecated alias of :c:func:PyImport_ImportModule.

.. versionchanged:: 3.3 This function used to fail immediately when the import lock was held by another thread. In Python 3.3 though, the locking scheme switched to per-module locks for most purposes, so this function's special behaviour isn't needed anymore.

.. c:function:: PyObject* PyImport_ImportModuleEx(const char *name, PyObject *globals, PyObject *locals, PyObject *fromlist)

.. index:: builtin: import

Import a module. This is best described by referring to the built-in Python function :func:__import__.

The return value is a new reference to the imported module or top-level package, or NULL with an exception set on failure. Like for :func:__import__, the return value when a submodule of a package was requested is normally the top-level package, unless a non-empty fromlist was given.

Failing imports remove incomplete module objects, like with :c:func:PyImport_ImportModule.

.. c:function:: PyObject* PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)

Import a module. This is best described by referring to the built-in Python function :func:__import__, as the standard :func:__import__ function calls this function directly.

.. versionadded:: 3.3

.. c:function:: PyObject* PyImport_ImportModuleLevel(const char *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)

Similar to :c:func:PyImport_ImportModuleLevelObject, but the name is a UTF-8 encoded string instead of a Unicode object.

.. versionchanged:: 3.3 Negative values for level are no longer accepted.

.. c:function:: PyObject* PyImport_Import(PyObject *name)

This is a higher-level interface that calls the current "import hook function" (with an explicit level of 0, meaning absolute import). It invokes the :func:__import__ function from the __builtins__ of the current globals. This means that the import is done using whatever import hooks are installed in the current environment.

This function always uses absolute imports.

.. c:function:: PyObject* PyImport_ReloadModule(PyObject *m)

Reload a module. Return a new reference to the reloaded module, or NULL with an exception set on failure (the module still exists in this case).

.. c:function:: PyObject* PyImport_AddModuleObject(PyObject *name)

Return the module object corresponding to a module name. The name argument may be of the form package.module. First check the modules dictionary if there's one there, and if not, create a new one and insert it in the modules dictionary. Return NULL with an exception set on failure.

.. note::

  This function does not load or import the module; if the module wasn't already
  loaded, you will get an empty module object. Use :c:func:`PyImport_ImportModule`
  or one of its variants to import a module.  Package structures implied by a
  dotted name for *name* are not created if not already present.

.. versionadded:: 3.3

.. c:function:: PyObject* PyImport_AddModule(const char *name)

Similar to :c:func:PyImport_AddModuleObject, but the name is a UTF-8 encoded string instead of a Unicode object.

.. c:function:: PyObject* PyImport_ExecCodeModule(const char *name, PyObject *co)

.. index:: builtin: compile

Given a module name (possibly of the form package.module) and a code object read from a Python bytecode file or obtained from the built-in function :func:compile, load the module. Return a new reference to the module object, or NULL with an exception set if an error occurred. name is removed from :attr:sys.modules in error cases, even if name was already in :attr:sys.modules on entry to :c:func:PyImport_ExecCodeModule. Leaving incompletely initialized modules in :attr:sys.modules is dangerous, as imports of such modules have no way to know that the module object is an unknown (and probably damaged with respect to the module author's intents) state.

The module's :attr:__spec__ and :attr:__loader__ will be set, if not set already, with the appropriate values. The spec's loader will be set to the module's __loader__ (if set) and to an instance of :class:SourceFileLoader otherwise.

The module's :attr:__file__ attribute will be set to the code object's :c:member:co_filename. If applicable, :attr:__cached__ will also be set.

This function will reload the module if it was already imported. See :c:func:PyImport_ReloadModule for the intended way to reload a module.

If name points to a dotted name of the form package.module, any package structures not already created will still not be created.

See also :c:func:PyImport_ExecCodeModuleEx and :c:func:PyImport_ExecCodeModuleWithPathnames.

.. c:function:: PyObject* PyImport_ExecCodeModuleEx(const char *name, PyObject *co, const char *pathname)

Like :c:func:PyImport_ExecCodeModule, but the :attr:__file__ attribute of the module object is set to pathname if it is non-NULL.

See also :c:func:PyImport_ExecCodeModuleWithPathnames.

.. c:function:: PyObject* PyImport_ExecCodeModuleObject(PyObject *name, PyObject *co, PyObject *pathname, PyObject *cpathname)

Like :c:func:PyImport_ExecCodeModuleEx, but the :attr:__cached__ attribute of the module object is set to cpathname if it is non-NULL. Of the three functions, this is the preferred one to use.

.. versionadded:: 3.3

.. c:function:: PyObject* PyImport_ExecCodeModuleWithPathnames(const char *name, PyObject *co, const char *pathname, const char *cpathname)

Like :c:func:PyImport_ExecCodeModuleObject, but name, pathname and cpathname are UTF-8 encoded strings. Attempts are also made to figure out what the value for pathname should be from cpathname if the former is set to NULL.

.. versionadded:: 3.2 .. versionchanged:: 3.3 Uses :func:imp.source_from_cache() in calculating the source path if only the bytecode path is provided.

.. c:function:: long PyImport_GetMagicNumber()

Return the magic number for Python bytecode files (a.k.a. :file:.pyc file). The magic number should be present in the first four bytes of the bytecode file, in little-endian byte order. Returns -1 on error.

.. versionchanged:: 3.3 Return value of -1 upon failure.

.. c:function:: const char * PyImport_GetMagicTag()

Return the magic tag string for :pep:3147 format Python bytecode file names. Keep in mind that the value at sys.implementation.cache_tag is authoritative and should be used instead of this function.

.. versionadded:: 3.2

.. c:function:: PyObject* PyImport_GetModuleDict()

Return the dictionary used for the module administration (a.k.a. sys.modules). Note that this is a per-interpreter variable.

.. c:function:: PyObject* PyImport_GetModule(PyObject *name)

Return the already imported module with the given name. If the module has not been imported yet then returns NULL but does not set an error. Returns NULL and sets an error if the lookup failed.

.. versionadded:: 3.7

.. c:function:: PyObject* PyImport_GetImporter(PyObject *path)

Return a finder object for a :data:sys.path/:attr:pkg.__path__ item path, possibly by fetching it from the :data:sys.path_importer_cache dict. If it wasn't yet cached, traverse :data:sys.path_hooks until a hook is found that can handle the path item. Return None if no hook could; this tells our caller that the :term:path based finder could not find a finder for this path item. Cache the result in :data:sys.path_importer_cache. Return a new reference to the finder object.

.. c:function:: void _PyImport_Init()

Initialize the import mechanism. For internal use only.

.. c:function:: void PyImport_Cleanup()

Empty the module table. For internal use only.

.. c:function:: void _PyImport_Fini()

Finalize the import mechanism. For internal use only.

.. c:function:: int PyImport_ImportFrozenModuleObject(PyObject *name)

Load a frozen module named name. Return 1 for success, 0 if the module is not found, and -1 with an exception set if the initialization failed. To access the imported module on a successful load, use :c:func:PyImport_ImportModule. (Note the misnomer --- this function would reload the module if it was already imported.)

.. versionadded:: 3.3

.. versionchanged:: 3.4 The __file__ attribute is no longer set on the module.

.. c:function:: int PyImport_ImportFrozenModule(const char *name)

Similar to :c:func:PyImport_ImportFrozenModuleObject, but the name is a UTF-8 encoded string instead of a Unicode object.

.. c:type:: struct _frozen

.. index:: single: freeze utility

This is the structure type definition for frozen module descriptors, as generated by the :program:freeze utility (see :file:Tools/freeze/ in the Python source distribution). Its definition, found in :file:Include/import.h, is::

  struct _frozen {
      const char *name;
      const unsigned char *code;
      int size;
  };

.. c:var:: const struct _frozen* PyImport_FrozenModules

This pointer is initialized to point to an array of :c:type:struct _frozen records, terminated by one whose members are all NULL or zero. When a frozen module is imported, it is searched in this table. Third-party code could play tricks with this to provide a dynamically created collection of frozen modules.

.. c:function:: int PyImport_AppendInittab(const char name, PyObject (*initfunc)(void))

Add a single module to the existing table of built-in modules. This is a convenience wrapper around :c:func:PyImport_ExtendInittab, returning -1 if the table could not be extended. The new module can be imported by the name name, and uses the function initfunc as the initialization function called on the first attempted import. This should be called before :c:func:Py_Initialize.

.. c:type:: struct _inittab

Structure describing a single entry in the list of built-in modules. Each of these structures gives the name and initialization function for a module built into the interpreter. The name is an ASCII encoded string. Programs which embed Python may use an array of these structures in conjunction with :c:func:PyImport_ExtendInittab to provide additional built-in modules. The structure is defined in :file:Include/import.h as::

  struct _inittab {
      const char *name;           /* ASCII encoded string */
      PyObject* (*initfunc)(void);
  };

.. c:function:: int PyImport_ExtendInittab(struct _inittab *newtab)

Add a collection of modules to the table of built-in modules. The newtab array must end with a sentinel entry which contains NULL for the :attr:name field; failure to provide the sentinel value can result in a memory fault. Returns 0 on success or -1 if insufficient memory could be allocated to extend the internal table. In the event of failure, no modules are added to the internal table. This should be called before :c:func:Py_Initialize.