5.3 Importing Modules
Keywords: api

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5.3 Importing Modules

PyObject* `PyImport_ImportModule` (char *name)
  Return value: New reference.
  This is a simplified interface to `PyImport_ImportModuleEx()` below, leaving the globals and locals arguments set to `NULL`. When the name argument contains a dot (i.e., 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 (the module may still be created in this case -- examine `sys.modules` to find out).

PyObject* `PyImport_ImportModuleEx` (char *name, PyObject *globals, PyObject *locals, PyObject *fromlist)
  Return value: New reference.
  Import a module. This is best described by referring to the built-in Python function `__import__()`, as the standard `__import__()` function calls this function directly.

  The return value is a new reference to the imported module or top-level package, or `NULL` with an exception set on failure (the module may still be created in this case). Like for `__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.

PyObject* `PyImport_Import` (PyObject *name)
  Return value: New reference.
  This is a higher-level interface that calls the current ``import hook function''. It invokes the `__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, e.g. by `rexec` or `ihooks`.

PyObject* `PyImport_ReloadModule` (PyObject *m)
  Return value: New reference.
  Reload a module. This is best described by referring to the built-in Python function `reload()`, as the standard `reload()` function calls this function directly. Return a new reference to the reloaded module, or `NULL` with an exception set on failure (the module still exists in this case).

PyObject* `PyImport_AddModule` (char *name)
  Return value: Borrowed reference.
  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 in in the modules dictionary. Warning: this function does not load or import the module; if the module wasn't already loaded, you will get an empty module object. Use `PyImport_ImportModule()` or one of its variants to import a module. Return `NULL` with an exception set on failure.

PyObject* `PyImport_ExecCodeModule` (char *name, PyObject *co)
  Return value: New reference.
  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 `compile()`, load the module. Return a new reference to the module object, or `NULL` with an exception set if an error occurred (the module may still be created in this case). (This function would reload the module if it was already imported.)

long `PyImport_GetMagicNumber` ()
  Return the magic number for Python bytecode files (a.k.a. .pyc and .pyo files). The magic number should be present in the first four bytes of the bytecode file, in little-endian byte order.

PyObject* `PyImport_GetModuleDict` ()
  Return value: Borrowed reference.
  Return the dictionary used for the module administration (a.k.a. `sys.modules`). Note that this is a per-interpreter variable.

void `_PyImport_Init` ()
  Initialize the import mechanism. For internal use only.

void `PyImport_Cleanup` ()
  Empty the module table. For internal use only.

void `_PyImport_Fini` ()
  Finalize the import mechanism. For internal use only.

PyObject* `_PyImport_FindExtension` (char *, char *)
  Return value: Borrowed reference.
  For internal use only.

PyObject* `_PyImport_FixupExtension` (char *, char *)
  For internal use only.

int `PyImport_ImportFrozenModule` (char *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 `PyImport_ImportModule()`. (Note the misnomer -- this function would reload the module if it was already imported.)

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

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

struct _frozen* `PyImport_FrozenModules`
  This pointer is initialized to point to an array of `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.

int `PyImport_AppendInittab` (char *name, void (*initfunc)(void))
  Add a single module to the existing table of built-in modules. This is a convenience wrapper around `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 `Py_Initialize()`.

`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. Programs which embed Python may use an array of these structures in conjunction with `PyImport_ExtendInittab()` to provide additional built-in modules. The structure is defined in Include/import.h as:

        struct _inittab {
            char *name;
            void (*initfunc)(void);
        };

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 `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 `Py_Initialize()`.