On Monday, August 22, 2011 12:06:44 PM UTC-7, Stephen Hansen wrote: > On 8/22/11 11:51 AM, Matthew Brett wrote: > > Hi, > > > > I recently ran into this behavior: > > > >>>> import sys > >>>> import apkg.subpkg > >>>> del sys.modules['apkg'] > >>>> import apkg.subpkg as subpkg > > Traceback (most recent call last): > > File "<stdin>", line 1, in <module> > > AttributeError: 'module' object has no attribute 'subpkg' > > > > where 'apkg' and 'subpkg' comprise empty __init__.py files to simplify the > > example. > > > > It appears then, that importing a subpackage, then deleting the containing > > package from sys.modules, orphans the subpackage in an unfixable state. > > > > I ran into this because the nose testing framework does exactly this kind > > of thing when loading test modules, causing some very confusing errors and > > failures. > > > > Is this behavior expected? > > Yes. Doing an import of "apkg.subpkg" results in more then just "test1" > being cached in sys.modules, and you're removing half of that so leaving > Python in a weird state. > > You also want to del sys.modules["apkg.subpkg"], then you'll be able to > re-import apkg.subpkg. I.e: > > Python 2.7.1 (r271:86882M, Nov 30 2010, 10:35:34) > [GCC 4.2.1 (Apple Inc. build 5664)] on darwin > Type "help", "copyright", "credits" or "license" for more information. > >>> import sys > >>> import test1.test2 > >>> del sys.modules['test1'] > >>> del sys.modules['test1.test2'] > >>> import test1.test2 as test2 > >>>
Yes, sorry, I should have mentioned that I explored these kind of variations. I think I see that there isn't an obvious way for del sys.modules['apkg'] to know to delete or modify 'apkg.subpkg', because sys.modules is just a dict. However, I could imagine the import machinery being able to recognize that 'apkg.subpkg' is broken, and re-import it without error. Is that reasonable? Best, Matthew -- http://mail.python.org/mailman/listinfo/python-list
