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+:mod:`pkgutil` --- Package extension utility
+============================================
+
+.. module:: pkgutil
+   :synopsis: Utilities for the import system.
+
+**Source code:** :source:`Lib/pkgutil.py`
+
+--------------
+
+This module provides utilities for the import system, in particular package
+support.
+
+.. class:: ModuleInfo(module_finder, name, ispkg)
+
+    A namedtuple that holds a brief summary of a module's info.
+
+    .. versionadded:: 3.6
+
+.. function:: extend_path(path, name)
+
+   Extend the search path for the modules which comprise a package.  Intended
+   use is to place the following code in a package's :file:`__init__.py`::
+
+      from pkgutil import extend_path
+      __path__ = extend_path(__path__, __name__)
+
+   This will add to the package's ``__path__`` all subdirectories of directories
+   on ``sys.path`` named after the package.  This is useful if one wants to
+   distribute different parts of a single logical package as multiple
+   directories.
+
+   It also looks for :file:`\*.pkg` files beginning where ``*`` matches the
+   *name* argument.  This feature is similar to :file:`\*.pth` files (see the
+   :mod:`site` module for more information), except that it doesn't special-case
+   lines starting with ``import``.  A :file:`\*.pkg` file is trusted at face
+   value: apart from checking for duplicates, all entries found in a
+   :file:`\*.pkg` file are added to the path, regardless of whether they exist
+   on the filesystem.  (This is a feature.)
+
+   If the input path is not a list (as is the case for frozen packages) it is
+   returned unchanged.  The input path is not modified; an extended copy is
+   returned.  Items are only appended to the copy at the end.
+
+   It is assumed that :data:`sys.path` is a sequence.  Items of :data:`sys.path`
+   that are not strings referring to existing directories are ignored. Unicode
+   items on :data:`sys.path` that cause errors when used as filenames may cause
+   this function to raise an exception (in line with :func:`os.path.isdir`
+   behavior).
+
+
+.. class:: ImpImporter(dirname=None)
+
+   :pep:`302` Finder that wraps Python's "classic" import algorithm.
+
+   If *dirname* is a string, a :pep:`302` finder is created that searches that
+   directory.  If *dirname* is ``None``, a :pep:`302` finder is created that
+   searches the current :data:`sys.path`, plus any modules that are frozen or
+   built-in.
+
+   Note that :class:`ImpImporter` does not currently support being used by
+   placement on :data:`sys.meta_path`.
+
+   .. deprecated:: 3.3
+      This emulation is no longer needed, as the standard import mechanism
+      is now fully PEP 302 compliant and available in :mod:`importlib`.
+
+
+.. class:: ImpLoader(fullname, file, filename, etc)
+
+   :term:`Loader` that wraps Python's "classic" import algorithm.
+
+   .. deprecated:: 3.3
+      This emulation is no longer needed, as the standard import mechanism
+      is now fully PEP 302 compliant and available in :mod:`importlib`.
+
+
+.. function:: find_loader(fullname)
+
+   Retrieve a module :term:`loader` for the given *fullname*.
+
+   This is a backwards compatibility wrapper around
+   :func:`importlib.util.find_spec` that converts most failures to
+   :exc:`ImportError` and only returns the loader rather than the full
+   :class:`ModuleSpec`.
+
+   .. versionchanged:: 3.3
+      Updated to be based directly on :mod:`importlib` rather than relying
+      on the package internal PEP 302 import emulation.
+
+   .. versionchanged:: 3.4
+      Updated to be based on :pep:`451`
+
+.. function:: get_importer(path_item)
+
+   Retrieve a :term:`finder` for the given *path_item*.
+
+   The returned finder is cached in :data:`sys.path_importer_cache` if it was
+   newly created by a path hook.
+
+   The cache (or part of it) can be cleared manually if a rescan of
+   :data:`sys.path_hooks` is necessary.
+
+   .. versionchanged:: 3.3
+      Updated to be based directly on :mod:`importlib` rather than relying
+      on the package internal PEP 302 import emulation.
+
+
+.. function:: get_loader(module_or_name)
+
+   Get a :term:`loader` object for *module_or_name*.
+
+   If the module or package is accessible via the normal import mechanism, a
+   wrapper around the relevant part of that machinery is returned.  Returns
+   ``None`` if the module cannot be found or imported.  If the named module is
+   not already imported, its containing package (if any) is imported, in order
+   to establish the package ``__path__``.
+
+   .. versionchanged:: 3.3
+      Updated to be based directly on :mod:`importlib` rather than relying
+      on the package internal PEP 302 import emulation.
+
+   .. versionchanged:: 3.4
+      Updated to be based on :pep:`451`
+
+
+.. function:: iter_importers(fullname='')
+
+   Yield :term:`finder` objects for the given module name.
+
+   If fullname contains a '.', the finders will be for the package
+   containing fullname, otherwise they will be all registered top level
+   finders (i.e. those on both sys.meta_path and sys.path_hooks).
+
+   If the named module is in a package, that package is imported as a side
+   effect of invoking this function.
+
+   If no module name is specified, all top level finders are produced.
+
+   .. versionchanged:: 3.3
+      Updated to be based directly on :mod:`importlib` rather than relying
+      on the package internal PEP 302 import emulation.
+
+
+.. function:: iter_modules(path=None, prefix='')
+
+   Yields :class:`ModuleInfo` for all submodules on *path*, or, if
+   *path* is ``None``, all top-level modules on ``sys.path``.
+
+   *path* should be either ``None`` or a list of paths to look for modules in.
+
+   *prefix* is a string to output on the front of every module name on output.
+
+   .. note::
+
+      Only works for a :term:`finder` which defines an ``iter_modules()``
+      method. This interface is non-standard, so the module also provides
+      implementations for :class:`importlib.machinery.FileFinder` and
+      :class:`zipimport.zipimporter`.
+
+   .. versionchanged:: 3.3
+      Updated to be based directly on :mod:`importlib` rather than relying
+      on the package internal PEP 302 import emulation.
+
+
+.. function:: walk_packages(path=None, prefix='', onerror=None)
+
+   Yields :class:`ModuleInfo` for all modules recursively on
+   *path*, or, if *path* is ``None``, all accessible modules.
+
+   *path* should be either ``None`` or a list of paths to look for modules in.
+
+   *prefix* is a string to output on the front of every module name on output.
+
+   Note that this function must import all *packages* (*not* all modules!) on
+   the given *path*, in order to access the ``__path__`` attribute to find
+   submodules.
+
+   *onerror* is a function which gets called with one argument (the name of the
+   package which was being imported) if any exception occurs while trying to
+   import a package.  If no *onerror* function is supplied, :exc:`ImportError`\s
+   are caught and ignored, while all other exceptions are propagated,
+   terminating the search.
+
+   Examples::
+
+      # list all modules python can access
+      walk_packages()
+
+      # list all submodules of ctypes
+      walk_packages(ctypes.__path__, ctypes.__name__ + '.')
+
+   .. note::
+
+      Only works for a :term:`finder` which defines an ``iter_modules()``
+      method. This interface is non-standard, so the module also provides
+      implementations for :class:`importlib.machinery.FileFinder` and
+      :class:`zipimport.zipimporter`.
+
+   .. versionchanged:: 3.3
+      Updated to be based directly on :mod:`importlib` rather than relying
+      on the package internal PEP 302 import emulation.
+
+
+.. function:: get_data(package, resource)
+
+   Get a resource from a package.
+
+   This is a wrapper for the :term:`loader`
+   :meth:`get_data <importlib.abc.ResourceLoader.get_data>` API.  The
+   *package* argument should be the name of a package, in standard module format
+   (``foo.bar``).  The *resource* argument should be in the form of a relative
+   filename, using ``/`` as the path separator.  The parent directory name
+   ``..`` is not allowed, and nor is a rooted name (starting with a ``/``).
+
+   The function returns a binary string that is the contents of the specified
+   resource.
+
+   For packages located in the filesystem, which have already been imported,
+   this is the rough equivalent of::
+
+      d = os.path.dirname(sys.modules[package].__file__)
+      data = open(os.path.join(d, resource), 'rb').read()
+
+   If the package cannot be located or loaded, or it uses a :term:`loader`
+   which does not support :meth:`get_data <importlib.abc.ResourceLoader.get_data>`,
+   then ``None`` is returned.  In particular, the :term:`loader` for
+   :term:`namespace packages <namespace package>` does not support
+   :meth:`get_data <importlib.abc.ResourceLoader.get_data>`.