[Python-Dev] PEP 420 - dynamic path computation is missing rationale

[PJ Eby]

On Wed, May 23, 2012 at 8:24 PM, Eric V. Smith <eric at 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.
>

Yay!
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