[Python-Dev] isolating import state during tests

Sun Apr 22 03:25:44 CEST 2012

On Sat, Apr 21, 2012 at 21:02, Eric Snow <ericsnowcurrently at gmail.com>wrote:
> It looks like the test suite accommodates a stable import state to
> some extent, but would it be worth having a PEP-405-esque context
> manager to help with this? For example, something along these lines:
>>> class ImportState:
> # sys.modules is part of the interpreter state, so
> # repopulate (don't replace)
> def __enter__(self):
> self.path = sys.path[:]
> self.modules = sys.modules.copy()
> self.meta_path = sys.meta_path[:]
> self.path_hooks = sys.path_hooks[:]
> self.path_importer_cache = sys.path_importer_cache.copy()
>> sys.path = site.getsitepackages()
> sys.modules.clear()
> sys.meta_path = []
> sys.path_hooks = []
> sys.path_importer_cache = {}
>> def __exit__(self, *args, **kwargs):
> sys.path = self.path
> sys.modules.clear()
> sys.modules.update(self.modules)
> sys.meta_path = self.meta_path
> sys.path_hooks = self.path_hooks
> sys.path_importer_cache = self.path_importer_cache
>>>> # in some unit test:
> with ImportState():
> ... # tests
>
That practically all done for you with a combination of
importlib.test.util.uncache and importlib.test.util.import_state.
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