By the way, you shouldn't name any real module abc, because there is also a standard Python module named abc, which can be used to create abstract base classes (or ABCs). By writing your own module named abc, you make the standard abc module very hard to load, and anything that uses import abc will import your module instead of the standard one.
I understand that your file probably isn't called abc, but naming conflicts can still be an issue. In general when you write a module it's a good idea to check if another module with the same name exists, simply by running import thing in the Python prompt. To find out where that module is located, see thing.__file__.
