The documentation is pretty opaque or non-existent on other aspects of importlib use, too. If I enable warnings, I see this (and many more like it). I've read PEP 302 a couple times, read the code in importlib that detects the warning and searched down several rabbit holes, only to come up empty...
T:\Python36\lib\importlib\_bootstrap.py:219: ImportWarning: can't resolve package from __spec__ or __package__, falling back on __name__ and __path__ My thoughts when I see it: "Ok. So what does that mean? Is it bad? It must be bad, otherwise I wouldn't get a warning. How do I reconcile __spec__ and __package__? Which one is missing and/or incorrect?" On Mon, Apr 16, 2018 at 9:36 AM, Paul Moore <p.f.mo...@gmail.com> wrote: > On 16 April 2018 at 17:22, Nick Coghlan <ncogh...@gmail.com> wrote: > > If we're not covering explicit __path__ manipulation anywhere, we > > should definitely mention that possibility. > > https://docs.python.org/3/library/pkgutil.html#pkgutil.extend_path > > does talk about it, but only in the context of scanning sys.path for > > matching names, not in the context of building a package from an > > arbitrary set of directory names. > > It's quite possible that we're not. > > > I'm not sure where we could put an explanation of some of the broader > > implications of that fact, though - while __path__ manipulation is > > usually fairly safe, we're always a little hesitant about encouraging > > too many dynamic modifications to the import system state, since it > > can sometimes have odd side effects based on whether imports happen > > before or after that state is adjusted.. > > One of the problems with PEP 302 was that there was no really good > place in the documentation to put all the information that was present > (certainly not in the version of the docs that was around when we > wrote it). So a lot of the important details remained buried in PEP > 302. Since then, a lot of the details ended up in the docs, mostly in > the importlib sections, but I don't recall ever seeing anything about > __path__ (and particularly not the nice summary you gave, "packages > are ultimately just modules with a > __path__ attribute that works like sys.path". > > Paul > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ >
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