Importing Modules — Python 2.7.18 documentation

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# Importing Modules

PyObject* `PyImport_ImportModule`(const char *name)
  Return value: New reference.

  This is a simplified interface to `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. Before Python 2.4, the module may still be created in the failure case — examine `sys.modules` to find out. Starting with Python 2.4, a failing import of a module no longer leaves the module in `sys.modules`.

  Changed in version 2.4: Failing imports remove incomplete module objects.

  Changed in version 2.6: Always uses absolute imports.

PyObject* `PyImport_ImportModuleNoBlock`(const char *name)

  This version of `PyImport_ImportModule()` does not block. It’s intended to be used in C functions that import other modules to execute a function. The import may block if another thread holds the import lock. The function `PyImport_ImportModuleNoBlock()` never blocks. It first tries to fetch the module from sys.modules and falls back to `PyImport_ImportModule()` unless the lock is held, in which case the function will raise an `ImportError`.

  New in version 2.6.

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 (before Python 2.4, 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.

  Changed in version 2.4: Failing imports remove incomplete module objects.

  Changed in version 2.6: The function is an alias for `PyImport_ImportModuleLevel()` with `-1` as level, meaning relative import.

PyObject* `PyImport_ImportModuleLevel`(char *name, PyObject *globals, PyObject *locals, PyObject *fromlist, int level)
  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. 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.

  New in version 2.5.

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`.

  Changed in version 2.6: Always uses absolute imports.

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`(const 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 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 `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.

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. Before Python 2.4, the module could still be created in error cases. Starting with Python 2.4, name is removed from `sys.modules` in error cases, and even if name was already in `sys.modules` on entry to `PyImport_ExecCodeModule()`. Leaving incompletely initialized modules in `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 `__file__` attribute will be set to the code object’s `co_filename`.

  This function will reload the module if it was already imported. See `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.

  Changed in version 2.4: name is removed from `sys.modules` in error cases.

PyObject* `PyImport_ExecCodeModuleEx`(char *name, PyObject *co, char *pathname)
  Return value: New reference.

  Like `PyImport_ExecCodeModule()`, but the `__file__` attribute of the module object is set to pathname if it is non-`NULL`.

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.

PyObject* `PyImport_GetImporter`(PyObject *path)

  Return an importer object for a `sys.path`/`pkg.__path__` item path, possibly by fetching it from the `sys.path_importer_cache` dict. If it wasn’t yet cached, traverse `sys.path_hooks` until a hook is found that can handle the path item. Return `None` if no hook could; this tells our caller it should fall back to the built-in import mechanism. Cache the result in `sys.path_importer_cache`. Return a new reference to the importer object.

  New in version 2.6.

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 *)

  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`(const 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()`.