[Python-Dev] PEP 420 - dynamic path computation is missing rationale (original) (raw)

Eric V. Smith eric at trueblade.com
Thu May 24 03:02:04 CEST 2012

On 5/23/2012 8:58 PM, PJ Eby wrote:

On Wed, May 23, 2012 at 8:24 PM, Eric V. Smith <eric at trueblade.com_ _<mailto: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.loadmodule(). I think that's reasonable, since loadmodule() 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 findmodule() 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 guess I could store the passed-in parent path, and use that if it can't be found through sys.modules.

I'm not sure I can conjure up code to test this.

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