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/Doc/library/pkgutil.rst

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 1
 2:mod:`pkgutil` --- Package extension utility
 3============================================
 4
 5.. module:: pkgutil
 6   :synopsis: Utilities to support extension of packages.
 7
 8
 9.. versionadded:: 2.3
10
11This module provides functions to manipulate packages:
12
13
14.. function:: extend_path(path, name)
15
16   Extend the search path for the modules which comprise a package. Intended use is
17   to place the following code in a package's :file:`__init__.py`::
18
19      from pkgutil import extend_path
20      __path__ = extend_path(__path__, __name__)
21
22   This will add to the package's ``__path__`` all subdirectories of directories on
23   ``sys.path`` named after the package.  This is useful if one wants to distribute
24   different parts of a single logical package as multiple directories.
25
26   It also looks for :file:`\*.pkg` files beginning where ``*`` matches the *name*
27   argument.  This feature is similar to :file:`\*.pth` files (see the :mod:`site`
28   module for more information), except that it doesn't special-case lines starting
29   with ``import``.  A :file:`\*.pkg` file is trusted at face value: apart from
30   checking for duplicates, all entries found in a :file:`\*.pkg` file are added to
31   the path, regardless of whether they exist on the filesystem.  (This is a
32   feature.)
33
34   If the input path is not a list (as is the case for frozen packages) it is
35   returned unchanged.  The input path is not modified; an extended copy is
36   returned.  Items are only appended to the copy at the end.
37
38   It is assumed that ``sys.path`` is a sequence.  Items of ``sys.path`` that are
39   not (Unicode or 8-bit) strings referring to existing directories are ignored.
40   Unicode items on ``sys.path`` that cause errors when used as filenames may cause
41   this function to raise an exception (in line with :func:`os.path.isdir`
42   behavior).
43
44.. function:: get_data(package, resource)
45
46   Get a resource from a package.
47
48   This is a wrapper for the PEP 302 loader :func:`get_data` API. The package
49   argument should be the name of a package, in standard module format
50   (foo.bar). The resource argument should be in the form of a relative
51   filename, using ``/`` as the path separator. The parent directory name
52   ``..`` is not allowed, and nor is a rooted name (starting with a ``/``).
53
54   The function returns a binary string that is the contents of the
55   specified resource.
56
57   For packages located in the filesystem, which have already been imported,
58   this is the rough equivalent of::
59
60       d = os.path.dirname(sys.modules[package].__file__)
61       data = open(os.path.join(d, resource), 'rb').read()
62
63   If the package cannot be located or loaded, or it uses a PEP 302 loader
64   which does not support :func:`get_data`, then None is returned.