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Implement the more specific PEP 302 semantics for loaders and what happens upon

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load failure in relation to reloads. Also expose
importlib.util.module_for_loader to handle all of the details of this along
with making sure all current loaders behave nicely.
This commit is contained in:
Brett Cannon 2009-02-17 02:45:03 +00:00
parent 0586ed6288
commit d2e7b33815
5 changed files with 159 additions and 62 deletions
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33
Doc/library/importlib.rst
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@ -151,3 +151,36 @@ find and load modules.
searched for a finder for the path entry and, if found, is stored in
:data:`sys.path_importer_cache` along with being queried about the
module.
:mod:`importlib.util` -- Utility code for importers
---------------------------------------------------
.. module:: importlib.util
:synopsis: Importers and path hooks
This module contains the various objects that help in the construction of
an :term:`importer`.
.. function:: module_for_loader(method)
A :term:`decorator` for a :term:`loader` which handles selecting the proper
module object to load with. The decorated method is expected to have a call
signature of ``method(self, module_object)`` for which the second argument
will be the module object to be used (note that the decorator will not work
on static methods because of the assumption of two arguments).
The decorated method will take in the name of the module to be loaded as
normal. If the module is not found in :data:`sys.modules` then a new one is
constructed with its :attr:`__name__` attribute set. Otherwise the module
found in :data:`sys.modules` will be passed into the method. If an
exception is raised by the decorated method and a module was added to
:data:`sys.modules` it will be removed to prevent a partially initialized
module from being in left in :data:`sys.modules` If an exception is raised
by the decorated method and a module was added to :data:`sys.modules` it
will be removed to prevent a partially initialized module from being in
left in :data:`sys.modules`. If the module was already in
:data:`sys.modules` then it is left alone.
Use of this decorator handles all the details of what module a loader
should use as specified by :pep:`302`.