[Python-Dev] pathlib - current status of discussions

[Brett Cannon]

On Wed, 13 Apr 2016 at 15:46 Nikolaus Rath <Nikolaus at rath.org> wrote:

> On Apr 13 2016, Brett Cannon <brett at python.org> wrote:
> > On Tue, 12 Apr 2016 at 22:38 Michael Mysinger via Python-Dev <
> > python-dev at python.org> wrote:
> >
> >> Ethan Furman <ethan <at> stoneleaf.us> writes:
> >>
> >> > Do we allow bytes to be returned from os.fspath()?  If yes, then do we
> >> > allow bytes from __fspath__()?
> >>
> >> De-lurking. Especially since the ultimate goal is better
> interoperability,
> >> I
> >> feel like an implementation that people can play with would help guide
> the
> >> few remaining decisions. To help test the various options you could
> >> temporarily add a _allow_bytes=GLOBAL_CONFIG_OPTION default argument to
> >> both
> >> pathlib.__fspath__() and os.fspath(), with distinct configurable
> defaults
> >> for
> >> each.
> >>
> >> In the spirit of Python 3 I feel like bytes might not be needed in
> >> practice,
> >> but something like this with defaults of False will allow people to
> easily
> >> test all the various options.
> >>
> >
> > https://gist.github.com/brettcannon/b3719f54715787d54a206bc011869aa1 has
> > the four potential approaches implemented (although it doesn't follow the
> > "separate functions" approach some are proposing and instead goes with
> the
> > allow_bytes approach I originally proposed).
>
>
> When passing an object that is of type str and has a __fspath__
> attribute, all approaches return the value of __fspath__().
>
> However, when passing something of type bytes, the second approach
> returns the object, while the third returns the value of __fspath__().
>
> Is this intentional? I think a __fspath__ attribute should always be
> preferred.
>

It's very much intentional. If we define __fspath__() to only return
strings but still want to minimize boilerplate of allowing bytes to simply
pass through without checking a path argument to see if it is bytes then
approach #2 is warranted. But if __fspath__() can return bytes then
approach #3 allows for it.
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