> Remi: Your use case is taken care of by `len(path.parts)`.

Yes, and your use case is taken care of by `len(str(path))` which works as well.

The reason in the PR is to simplify:

sorted(paths, key=lambda path: len(str(path)), reverse=True)

to 

sorted(paths, key=len, reverse=True)

but why avoiding a few characters?


My remark is not that it __len__ should be len(path.parts) but that the semantics are unclear (I should have wrote "**if __len__ is defined** I would expect...")


Since the semantics are unclear I would except it not to be defined. Also, it's common to use a lambda or an helper function in sorted(), map(), filter(), etc. Most use case can't be covered using existing methods and shouldn't necessarely be.