On Wed, May 23, 2012 at 8:24 PM, Eric V. Smith <eric@trueblade.com> wrote:
I tried this approach and it works fine. The only caveat is that it
assumes that the parent path can always be computed as described above,
independent of what's passed in to PathFinder.load_module(). I think
that's reasonable, since load_module() itself hard-codes sys.path if the
supplied path is missing.

Technically, PEP 302 says that finders aren't allowed to assume their parent packages are imported:

""" However, the find_module() method isn't necessarily always called during an actual import: meta tools that analyze import dependencies (such as freeze, Installer or py2exe) don't actually load modules, so a finder shouldn't depend on the parent package being available in sys.modules."""

OTOH, that's finders, and I think we're dealing with loaders here.  Splitting hairs, perhaps, but at least it's in a good cause.  ;-)

I've checked this in to the pep-420 branch. I prefer this approach over
Nick's because it doesn't require any changes to any existing
interfaces. The changes are contained to the namespace package code and
don't affect other code in importlib.

Assuming this approach is acceptable, I'm done with the PEP except for
adding some examples.

And I'm done with the implementation except for adding tests and a few
small tweaks.