271 lines
10 KiB
ReStructuredText
271 lines
10 KiB
ReStructuredText
:mod:`pkgutil` --- Package extension utility
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============================================
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.. module:: pkgutil
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:synopsis: Utilities for the import system.
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**Source code:** :source:`Lib/pkgutil.py`
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--------------
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This module provides utilities for the import system, in particular package
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support.
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.. class:: ModuleInfo(module_finder, name, ispkg)
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A namedtuple that holds a brief summary of a module's info.
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.. versionadded:: 3.6
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.. function:: extend_path(path, name)
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Extend the search path for the modules which comprise a package. Intended
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use is to place the following code in a package's :file:`__init__.py`::
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from pkgutil import extend_path
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__path__ = extend_path(__path__, __name__)
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This will add to the package's ``__path__`` all subdirectories of directories
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on ``sys.path`` named after the package. This is useful if one wants to
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distribute different parts of a single logical package as multiple
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directories.
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It also looks for :file:`\*.pkg` files beginning where ``*`` matches the
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*name* argument. This feature is similar to :file:`\*.pth` files (see the
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:mod:`site` module for more information), except that it doesn't special-case
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lines starting with ``import``. A :file:`\*.pkg` file is trusted at face
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value: apart from checking for duplicates, all entries found in a
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:file:`\*.pkg` file are added to the path, regardless of whether they exist
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on the filesystem. (This is a feature.)
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If the input path is not a list (as is the case for frozen packages) it is
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returned unchanged. The input path is not modified; an extended copy is
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returned. Items are only appended to the copy at the end.
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It is assumed that :data:`sys.path` is a sequence. Items of :data:`sys.path`
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that are not strings referring to existing directories are ignored. Unicode
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items on :data:`sys.path` that cause errors when used as filenames may cause
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this function to raise an exception (in line with :func:`os.path.isdir`
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behavior).
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.. class:: ImpImporter(dirname=None)
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:pep:`302` Finder that wraps Python's "classic" import algorithm.
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If *dirname* is a string, a :pep:`302` finder is created that searches that
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directory. If *dirname* is ``None``, a :pep:`302` finder is created that
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searches the current :data:`sys.path`, plus any modules that are frozen or
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built-in.
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Note that :class:`ImpImporter` does not currently support being used by
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placement on :data:`sys.meta_path`.
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.. deprecated:: 3.3
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This emulation is no longer needed, as the standard import mechanism
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is now fully :pep:`302` compliant and available in :mod:`importlib`.
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.. class:: ImpLoader(fullname, file, filename, etc)
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:term:`Loader <loader>` that wraps Python's "classic" import algorithm.
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.. deprecated:: 3.3
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This emulation is no longer needed, as the standard import mechanism
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is now fully :pep:`302` compliant and available in :mod:`importlib`.
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.. function:: find_loader(fullname)
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Retrieve a module :term:`loader` for the given *fullname*.
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This is a backwards compatibility wrapper around
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:func:`importlib.util.find_spec` that converts most failures to
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:exc:`ImportError` and only returns the loader rather than the full
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:class:`ModuleSpec`.
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.. versionchanged:: 3.3
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Updated to be based directly on :mod:`importlib` rather than relying
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on the package internal :pep:`302` import emulation.
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.. versionchanged:: 3.4
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Updated to be based on :pep:`451`
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.. function:: get_importer(path_item)
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Retrieve a :term:`finder` for the given *path_item*.
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The returned finder is cached in :data:`sys.path_importer_cache` if it was
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newly created by a path hook.
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The cache (or part of it) can be cleared manually if a rescan of
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:data:`sys.path_hooks` is necessary.
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.. versionchanged:: 3.3
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Updated to be based directly on :mod:`importlib` rather than relying
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on the package internal :pep:`302` import emulation.
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.. function:: get_loader(module_or_name)
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Get a :term:`loader` object for *module_or_name*.
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If the module or package is accessible via the normal import mechanism, a
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wrapper around the relevant part of that machinery is returned. Returns
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``None`` if the module cannot be found or imported. If the named module is
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not already imported, its containing package (if any) is imported, in order
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to establish the package ``__path__``.
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.. versionchanged:: 3.3
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Updated to be based directly on :mod:`importlib` rather than relying
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on the package internal :pep:`302` import emulation.
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.. versionchanged:: 3.4
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Updated to be based on :pep:`451`
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.. function:: iter_importers(fullname='')
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Yield :term:`finder` objects for the given module name.
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If fullname contains a '.', the finders will be for the package
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containing fullname, otherwise they will be all registered top level
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finders (i.e. those on both sys.meta_path and sys.path_hooks).
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If the named module is in a package, that package is imported as a side
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effect of invoking this function.
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If no module name is specified, all top level finders are produced.
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.. versionchanged:: 3.3
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Updated to be based directly on :mod:`importlib` rather than relying
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on the package internal :pep:`302` import emulation.
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.. function:: iter_modules(path=None, prefix='')
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Yields :class:`ModuleInfo` for all submodules on *path*, or, if
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*path* is ``None``, all top-level modules on ``sys.path``.
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*path* should be either ``None`` or a list of paths to look for modules in.
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*prefix* is a string to output on the front of every module name on output.
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.. note::
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Only works for a :term:`finder` which defines an ``iter_modules()``
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method. This interface is non-standard, so the module also provides
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implementations for :class:`importlib.machinery.FileFinder` and
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:class:`zipimport.zipimporter`.
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.. versionchanged:: 3.3
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Updated to be based directly on :mod:`importlib` rather than relying
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on the package internal :pep:`302` import emulation.
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.. function:: walk_packages(path=None, prefix='', onerror=None)
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Yields :class:`ModuleInfo` for all modules recursively on
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*path*, or, if *path* is ``None``, all accessible modules.
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*path* should be either ``None`` or a list of paths to look for modules in.
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*prefix* is a string to output on the front of every module name on output.
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Note that this function must import all *packages* (*not* all modules!) on
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the given *path*, in order to access the ``__path__`` attribute to find
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submodules.
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*onerror* is a function which gets called with one argument (the name of the
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package which was being imported) if any exception occurs while trying to
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import a package. If no *onerror* function is supplied, :exc:`ImportError`\s
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are caught and ignored, while all other exceptions are propagated,
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terminating the search.
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Examples::
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# list all modules python can access
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walk_packages()
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# list all submodules of ctypes
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walk_packages(ctypes.__path__, ctypes.__name__ + '.')
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.. note::
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Only works for a :term:`finder` which defines an ``iter_modules()``
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method. This interface is non-standard, so the module also provides
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implementations for :class:`importlib.machinery.FileFinder` and
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:class:`zipimport.zipimporter`.
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.. versionchanged:: 3.3
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Updated to be based directly on :mod:`importlib` rather than relying
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on the package internal :pep:`302` import emulation.
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.. function:: get_data(package, resource)
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Get a resource from a package.
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This is a wrapper for the :term:`loader`
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:meth:`get_data <importlib.abc.ResourceLoader.get_data>` API. The
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*package* argument should be the name of a package, in standard module format
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(``foo.bar``). The *resource* argument should be in the form of a relative
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filename, using ``/`` as the path separator. The parent directory name
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``..`` 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
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resource.
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For packages located in the filesystem, which have already been imported,
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this is the rough equivalent of::
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d = os.path.dirname(sys.modules[package].__file__)
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data = open(os.path.join(d, resource), 'rb').read()
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If the package cannot be located or loaded, or it uses a :term:`loader`
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which does not support :meth:`get_data <importlib.abc.ResourceLoader.get_data>`,
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then ``None`` is returned. In particular, the :term:`loader` for
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:term:`namespace packages <namespace package>` does not support
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:meth:`get_data <importlib.abc.ResourceLoader.get_data>`.
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.. function:: resolve_name(name)
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Resolve a name to an object.
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This functionality is used in numerous places in the standard library (see
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:issue:`12915`) - and equivalent functionality is also in widely used
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third-party packages such as setuptools, Django and Pyramid.
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It is expected that *name* will be a string in one of the following
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formats, where W is shorthand for a valid Python identifier and dot stands
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for a literal period in these pseudo-regexes:
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* ``W(.W)*``
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* ``W(.W)*:(W(.W)*)?``
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The first form is intended for backward compatibility only. It assumes that
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some part of the dotted name is a package, and the rest is an object
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somewhere within that package, possibly nested inside other objects.
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Because the place where the package stops and the object hierarchy starts
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can't be inferred by inspection, repeated attempts to import must be done
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with this form.
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In the second form, the caller makes the division point clear through the
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provision of a single colon: the dotted name to the left of the colon is a
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package to be imported, and the dotted name to the right is the object
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hierarchy within that package. Only one import is needed in this form. If
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it ends with the colon, then a module object is returned.
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The function will return an object (which might be a module), or raise one
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of the following exceptions:
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:exc:`ValueError` -- if *name* isn't in a recognised format.
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:exc:`ImportError` -- if an import failed when it shouldn't have.
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:exc:`AttributeError` -- If a failure occurred when traversing the object
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hierarchy within the imported package to get to the desired object.
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.. versionadded:: 3.9
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