At 12:37 PM 7/20/2011 -0400, Erik wrote:

The best solution I can think of would be to have a way for a module to mark itself as "finalized" (I'm not sure if that's the best term--just the first that popped into my head). This would prevent its __path__ from being created or extended in any way. For example, if the json module contains `__finalized__ = True` or something of the like, any `import json.foo` would immediately fail.

That wouldn't actually fix the problem Jeff brought up, which was the case where there *wasn't* a json.py. In any case, we can fix this now by banning direct import of pure-virtual packages.

In that case there would need to be a way to mark a directory as not containing importable code. Not sure what the best approach to that would be, especially since one of the goals of this PEP seems to be to avoid marker files.

For this particular issue, we don't need it. For tools that process Python code, or use pkgutil.walk_modules(), there may still be use cases, so we'll keep an eye open for relevant input. Hopefully someone will say something that jars loose an idea or two, as happened with Jeff's issue above. (Btw, as we speak, I am swiping Jeff's example and adding it into the PEP. ;-) It makes a great motivating example for banning pure-virtual package imports.)