[Python-Dev] Defining a path protocol (original) (raw)

Brett Cannon brett at python.org
Wed Apr 6 13:41:14 EDT 2016

On Wed, 6 Apr 2016 at 10:36 Michel Desmoulin <desmoulinmichel at gmail.com> wrote:

Wouldn't be better to generalize that to a "location" protocol, which allow to return any kind of location, including path, url or coordinate, ipaddress, etc ?

No because all of those things have different semantic meaning. See the index PEP for reasons why you would tightly bound protocols instead of overloading ones like int for multiple meanings.

-Brett

Le 06/04/2016 19:26, Brett Cannon a écrit : > 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 PyObjectPath()? > > > 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 <ethan at stoneleaf.us_ _> <mailto:ethan at stoneleaf.us>> wrote: > > On 04/05/2016 11:57 PM, Nick Coghlan wrote: > > On 6 April 2016 at 16:53, Nathaniel Smith <njs at pobox.com_ _> <mailto:njs at pobox.com>> wrote: > >> On Tue, Apr 5, 2016 at 11:29 PM, Nick Coghlan <ncoghlan at gmail.com_ _> <mailto:ncoghlan at 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. > > > _> ________________________ > Python-Dev mailing list > Python-Dev at python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/desmoulinmichel%40gmail.com >

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