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Introduce importlib.abc. The module contains various ABCs related to imports
(mostly stuff specified by PEP 302). There are two ABCs, PyLoader and PyPycLoader, which help with implementing source and source/bytecode loaders by implementing load_module in terms of other methods. This removes a lot of gritty details loaders typically have to worry about.
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Brett Cannon
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9 changed files with 739 additions and 171 deletions
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@ -82,6 +82,175 @@ Functions
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occuring from to already be imported (i.e., *package* must already be
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imported).
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:mod:`importlib.abc` -- Abstract base classes related to import
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---------------------------------------------------------------
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.. module:: importlib.abc
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:synopsis: Abstract base classes related to import
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The :mod:`importlib.abc` module contains all of the core abstract base classes
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used by :keyword:`import`. Some subclasses of the core abstract base classes
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are also provided to help in implementing the core ABCs.
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.. class:: Finder
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An abstract base class representing a :term:`finder`.
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..method:: find_module(fullname, path=None)
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An abstract method for finding a :term:`loader` for the specified
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module. If the :term:`finder` is found on :data:`sys.meta_path` and the
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module to be searched for is a subpackage or module then *path* is set
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to the value of :attr:`__path__` from the parent package. If a loader
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cannot be found, :keyword:`None` is returned.
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The exact definition of a :term:`finder` can be found in :pep:`302`.
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.. class:: Loader
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An abstract base class for a :term:`loader`.
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..method:: load_module(fullname)
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An abstract method for loading a module. If the module cannot be
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loaded, :exc:`ImportError` is raised, otherwise the loaded module is
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returned.
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If the requested module is already exists in :data:`sys.modules`, that
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module should be used and reloaded.
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Otherwise a new module is to be created by the loader and inserted into
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:data:`sys.modules`before any loading begins to prevent recursion from
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the import. If the loader inserted into a module and the load fails it
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must be removed by the loader from :data:`sys.modules`; modules already
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in :data:`sys.modules` before the loader began execution should be left
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alone. The :func:`importlib.util.module_for_loader` decorator handles
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all of these details.
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The loader is expected to set several attributes on the module when
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adding a new module to :data:`sys.modules`.
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- :attr:`__name__`
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The name of the module.
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- :attr:`__file__`
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The path to where the module data is stored (not set for built-in
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modules).
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- :attr:`__path__`
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Set to a list of strings specifying the search path within a
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package. This attribute is not set on modules.
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- :attr:`__package__`
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The parent package for the module/package. If the module is
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top-level then it has a value of the empty string. The
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:func:`importlib.util.set_package` decorator can handle the details
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for :attr:`__package__`.
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- :attr:`__loader__`
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Set to the loader used to load the module.
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See :pep:`302` for the exact definition for a loader.
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.. class:: ResourceLoader
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An abstract base class for a :term:`loader` which implements the optional
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:pep:`302` protocol for loading arbitrary resources from the storage
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back-end.
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..method:: get_data(path)
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An abstract method to return the bytes for the data located at *path*.
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Loaders that have a file-like storage back-end can implement this
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abstract method to give direct access
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to the data stored. :exc:`IOError` is to be raised if the *path* cannot
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be found. The *path* is expected to be constructed using a module's
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:attr:`__path__` attribute or an item from :attr:`__path__`.
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.. class:: InspectLoader
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An abstract base class for a :term:`loader` which implements the optional
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:pep:`302` protocol for loaders which inspect modules.
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..method:: is_package(fullname)
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An abstract method to return a true value if the module is a package, a
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false value otherwise. :exc:`ImportError` is raised if the
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:term:`loader` cannot find the module.
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..method:: get_source(fullname)
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An abstract method to return the source of a module. It is returned as
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a string with universal newline support. Returns :keyword:`None` if no
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source is available (e.g. a built-in module). Raises :exc:`ImportError`
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if the loader cannot find the module specified.
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..method:: get_code(fullname)
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An abstract method to return the :class:`code` object for a module.
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:keyword:`None` is returned if the module does not have a code object
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(e.g. built-in module). :exc:`ImportError` is raised if loader cannot
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find the requested module.
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.. class:: PyLoader
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An abstract base class inheriting from :class:`importlib.abc.InspectLoader`
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and :class:`importlib.abc.ResourceLoader` designed to ease the loading of
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Python source modules (bytecode is not handled; see
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:class:`importlib.abc.PyPycLoader` for a source/bytecode ABC). A subclass
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implementing this ABC will only need to worry about exposing how the source
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code is stored; all other details for loading Python source code will be
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handled by the concrete implementations of key methods.
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..method:: source_path(fullname)
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An abstract method that returns the path to the source code for a
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module. Should return :keyword:`None` if there is no source code.
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:exc:`ImportError` if the module cannot be found.
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..method:: load_module(fullname)
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A concrete implementation of :meth:`importlib.abc.Loader.load_module`
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that loads Python source code.
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..method:: get_code(fullname)
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A concrete implementation of
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:meth:`importlib.abc.InspectLoader.get_code` that creates code objects
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from Python source code.
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.. class:: PyPycLoader
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An abstract base class inheriting from :class:`importlib.abc.PyLoader`.
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This ABC is meant to help in creating loaders that support both Python
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source and bytecode.
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..method:: source_mtime(fullname)
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An abstract method which returns the modification time for the source
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code of the specified module. The modification time should be an
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integer. If there is no source code, return :keyword:`None. If the
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module cannot be found then :exc:`ImportError` is raised.
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..method:: bytecode_path(fullname)
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An abstract method which returns the path to the bytecode for the
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specified module. :keyword:`None` is returned if there is no bytecode.
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:exc:`ImportError` is raised if the module is not found.
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..method:: write_bytecode(fullname, bytecode)
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An abstract method which has the loader write *bytecode* for future
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use. If the bytecode is written, return :keyword:`True`. Return
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:keyword:`False` if the bytecode could not be written. This method
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should not be called if :data:`sys.dont_write_bytecode` is true.
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:mod:`importlib.machinery` -- Importers and path hooks
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------------------------------------------------------
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@ -93,44 +262,27 @@ find and load modules.
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.. class:: BuiltinImporter
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:term:`Importer` for built-in modules. All known built-in modules are
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listed in :data:`sys.builtin_module_names`.
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An :term:`importer` for built-in modules. All known built-in modules are
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listed in :data:`sys.builtin_module_names`. This class implements the
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:class:`importlib.abc.Finder` and :class:`importlib.abc.Loader` ABCs.
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Only class methods are defined by this class to alleviate the need for
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instantiation.
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.. classmethod:: find_module(fullname, path=None)
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Class method that allows this class to be a :term:`finder` for built-in
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modules.
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.. classmethod:: load_module(fullname)
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Class method that allows this class to be a :term:`loader` for built-in
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modules.
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.. class:: FrozenImporter
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:term:`Importer` for frozen modules.
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An :term:`importer` for frozen modules. This class implements the
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:class:`importlib.abc.Finder` and :class:`importlib.abc.Loader` ABCs.
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Only class methods are defined by this class to alleviate the need for
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instantiation.
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.. classmethod:: find_module(fullname, path=None)
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Class method that allows this class to be a :term:`finder` for frozen
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modules.
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.. classmethod:: load_module(fullname)
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Class method that allows this class to be a :term:`loader` for frozen
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modules.
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.. class:: PathFinder
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:term:`Finder` for :data:`sys.path`.
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:term:`Finder` for :data:`sys.path`. This class implements the
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:class:`importlib.abc.Finder` ABC.
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This class does not perfectly mirror the semantics of :keyword:`import` in
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terms of :data:`sys.path`. No implicit path hooks are assumed for
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@ -142,15 +294,15 @@ find and load modules.
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.. classmethod:: find_module(fullname, path=None)
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Class method that attempts to find a :term:`loader` for the module
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specified by *fullname* either on :data:`sys.path` or, if defined, on
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specified by *fullname* on :data:`sys.path` or, if defined, on
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*path*. For each path entry that is searched,
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:data:`sys.path_importer_cache` is checked. If an non-false object is
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found then it is used as the :term:`finder` to query for the module
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being searched for. For no entry is found in
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found then it is used as the :term:`finder` to look for the module
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being searched for. If no entry is found in
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:data:`sys.path_importer_cache`, then :data:`sys.path_hooks` is
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searched for a finder for the path entry and, if found, is stored in
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:data:`sys.path_importer_cache` along with being queried about the
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module.
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module. If no finder is ever found then :keyword:`None` is returned.
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:mod:`importlib.util` -- Utility code for importers
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@ -166,10 +318,11 @@ an :term:`importer`.
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A :term:`decorator` for a :term:`loader` which handles selecting the proper
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module object to load with. The decorated method is expected to have a call
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signature of ``method(self, module_object)`` for which the second argument
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will be the module object to be used by the loader (note that the decorator
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signature taking two positional arguments
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(e.g. ``load_module(self, module)``) for which the second argument
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will be the module object to be used by the loader. Note that the decorator
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will not work on static methods because of the assumption of two
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arguments).
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arguments.
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The decorated method will take in the name of the module to be loaded as
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expected for a :term:`loader`. If the module is not found in
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