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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.
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