cpython/Doc/library/pkgutil.rst

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:mod:`pkgutil` --- Package extension utility
============================================
.. module:: pkgutil
:synopsis: Utilities to support extension of packages.
.. versionadded:: 2.3
This module provides functions to manipulate packages:
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.. 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.
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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 ``/``).
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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.