[SOLVED] Cannot import from package in same namespace tree until pkg

Cannot import from package in same namespace tree until pkg_resources has been imported

I have a strange problem that I somehow cannot reproduce separately, yet it shows up in production code, and of course the production code cannot be shared publically.

I have two packages, for argument's sake ns.server and ns.protobuf, where the latter implements protobuf specific extensions for the project. Both packages properly declare the namespace packages in setup.py, and both have the boilerplate pkg_resources stuff in __init__.py:

try:
    __import__('pkg_resources').declare_namespace(__name__)
except ImportError:
    from pkgutil import extend_path
    __path__ = extend_path(__path__, __name__)

Now for some strange reason, I get this:

>>> import ns.protobuf
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named protobuf
>>> import pkg_resources
>>> import ns.protobuf
>>>

So it appears that my namespaces are all screwy until I import pkg_resources and then it is fixed. It's not too bad, the workaround is then simply to import pkg_resources first. I would just like to understand what is going on.

Solution

Ugh, second question I self-answer in as many days. I had a stale egg-info directory lying around in lib/python2.7/site-packages, from a previous install where I accidentally neglected to pass -e (development mode) to pip. Completely clearing everything and reinstalling fixed it.