Error when deleting and reimporting subpackages

[John Nagle]

On 8/22/2011 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?

    It's undefined behavior.  You're dealing with CPython implementation
semantics, not Python language semantics.

				John Nagle