
:mod:`pkgutil` --- Package extension utility
============================================

.. module:: pkgutil
   :synopsis: Utilities to support extension of packages.


.. versionadded:: 2.3

This module provides functions to manipulate packages:


.. 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 ``sys.path`` is a sequence.  Items of ``sys.path`` that are
   not (Unicode or 8-bit) strings referring to existing directories are ignored.
   Unicode items on ``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).

.. function:: get_data(package, resource)

   Get a resource from a package.

   This is a wrapper for the PEP 302 loader :func:`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 PEP 302 loader
   which does not support :func:`get_data`, then None is returned.
