WIth Ethan volunteering to do the work to help make a path protocol a thing -- and I'm willing to help along with propagating this through the stdlib where I think Serhiy might be interested in helping as well -- and a seeming consensus this is a good idea, it seems like this proposal has a chance of actually coming to fruition.
Now we need clear details. :) Some open questions are: 1. Name: __path__, __fspath__, or something else? 2. Method or attribute? (changes what kind of one-liner you might use in libraries, but I think historically all protocols have been methods and the serialized string representation might be costly to build) 3. Built-in? (name is dependent on #1 if we add one) 4. Add the method/attribute to str? (I assume so, much like __index__() is on int, but I have not seen it explicitly stated so I would rather clarify it) 5. Expand the C API to have something like PyObject_Path()? Some people have asked for the pathlib PEP to have a more flushed out reasoning as to why pathlib doesn't inherit from str. If Antoine doesn't want to do it I can try to instil my blog post into a more succinct paragraph or two and update the PEP myself. Is this going to require a PEP or if we can agree on the points here are we just going to do it? If we think it requires a PEP I'm willing to write it, but I obviously have no issue if we skip that step either. :) Oh, and we should resolve this before the next release of Python 3.4, 3.5, or 3.6 so that pathlib can be updated in those releases. -Brett On Wed, 6 Apr 2016 at 08:09 Ethan Furman <et...@stoneleaf.us> wrote: > On 04/05/2016 11:57 PM, Nick Coghlan wrote: > > On 6 April 2016 at 16:53, Nathaniel Smith <n...@pobox.com> wrote: > >> On Tue, Apr 5, 2016 at 11:29 PM, Nick Coghlan <ncogh...@gmail.com> > wrote: > > >>> I'd missed the existing precedent in DirEntry.path, so simply taking > >>> that and running with it sounds good to me. > >> > >> This makes me twitch slightly, because NumPy has had a whole set of > >> problems due to the ancient and minimally-considered decision to > >> assume a bunch of ad hoc non-namespaced method names fulfilled some > >> protocol -- like all .sum methods will have a signature that's > >> compatible with numpy's, and if an object has a .log method then > >> surely that computes the logarithm (what else in computing could "log" > >> possibly refer to?), etc. This experience may or may not be relevant, > >> I'm not sure -- sometimes these kinds of twitches are good guides to > >> intuition, and sometimes they are just knee-jerk responses to an old > >> and irrelevant problem :-) > >> > >> But you might want to at least think about > >> how common it might be to have existing objects with unrelated > >> attributes that happen to be called "path", and the bizarro problems > >> that might be caused if someone accidentally passes one of them to a > >> function that expects all .path attributes to be instances of this new > >> protocol. > > > > sys.path, for example. > > > > That's why I'd actually prefer the implicit conversion protocol to be > > the more explicitly named "__fspath__", with suitable "__fspath__ = > > path" assignments added to DirEntry and pathlib. However, I'm also not > > offering to actually *do* the work here, and the casting vote goes to > > the folks pursuing the implementation effort. > > If we decide upon __fspath__ (or __path__) I will do the work on pathlib > and scandir to add those attributes.
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