191 lines
7.5 KiB
ReStructuredText
191 lines
7.5 KiB
ReStructuredText
: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.
|
|
|
|
|
|
.. 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` Importer that wraps Python's "classic" import algorithm.
|
|
|
|
If *dirname* is a string, a :pep:`302` importer is created that searches that
|
|
directory. If *dirname* is ``None``, a :pep:`302` importer 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`.
|
|
|
|
|
|
.. class:: ImpLoader(fullname, file, filename, etc)
|
|
|
|
:pep:`302` Loader that wraps Python's "classic" import algorithm.
|
|
|
|
|
|
.. function:: find_loader(fullname)
|
|
|
|
Find a :pep:`302` "loader" object for *fullname*.
|
|
|
|
If *fullname* contains dots, path must be the containing package's
|
|
``__path__``. Returns ``None`` if the module cannot be found or imported.
|
|
This function uses :func:`iter_importers`, and is thus subject to the same
|
|
limitations regarding platform-specific special import locations such as the
|
|
Windows registry.
|
|
|
|
|
|
.. function:: get_importer(path_item)
|
|
|
|
Retrieve a :pep:`302` importer for the given *path_item*.
|
|
|
|
The returned importer is cached in :data:`sys.path_importer_cache` if it was
|
|
newly created by a path hook.
|
|
|
|
If there is no importer, a wrapper around the basic import machinery is
|
|
returned. This wrapper is never inserted into the importer cache (``None``
|
|
is inserted instead).
|
|
|
|
The cache (or part of it) can be cleared manually if a rescan of
|
|
:data:`sys.path_hooks` is necessary.
|
|
|
|
|
|
.. function:: get_loader(module_or_name)
|
|
|
|
Get a :pep:`302` "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__``.
|
|
|
|
This function uses :func:`iter_importers`, and is thus subject to the same
|
|
limitations regarding platform-specific special import locations such as the
|
|
Windows registry.
|
|
|
|
|
|
.. function:: iter_importers(fullname='')
|
|
|
|
Yield :pep:`302` importers for the given module name.
|
|
|
|
If fullname contains a '.', the importers will be for the package containing
|
|
fullname, otherwise they will be importers for :data:`sys.meta_path`,
|
|
:data:`sys.path`, and Python's "classic" import machinery, in that order. If
|
|
the named module is in a package, that package is imported as a side effect
|
|
of invoking this function.
|
|
|
|
Non-:pep:`302` mechanisms (e.g. the Windows registry) used by the standard
|
|
import machinery to find files in alternative locations are partially
|
|
supported, but are searched *after* :data:`sys.path`. Normally, these
|
|
locations are searched *before* :data:`sys.path`, preventing :data:`sys.path`
|
|
entries from shadowing them.
|
|
|
|
For this to cause a visible difference in behaviour, there must be a module
|
|
or package name that is accessible via both :data:`sys.path` and one of the
|
|
non-:pep:`302` file system mechanisms. In this case, the emulation will find
|
|
the former version, while the builtin import mechanism will find the latter.
|
|
|
|
Items of the following types can be affected by this discrepancy:
|
|
``imp.C_EXTENSION``, ``imp.PY_SOURCE``, ``imp.PY_COMPILED``,
|
|
``imp.PKG_DIRECTORY``.
|
|
|
|
|
|
.. function:: iter_modules(path=None, prefix='')
|
|
|
|
Yields ``(module_loader, name, ispkg)`` 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.
|
|
|
|
|
|
.. function:: walk_packages(path=None, prefix='', onerror=None)
|
|
|
|
Yields ``(module_loader, name, ispkg)`` 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__ + '.')
|
|
|
|
|
|
.. 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.
|