[Python-Dev] Pathlib enhancements - acceptable inputs and outputs for __fspath__ and os.fspath()

[Stephen J. Turnbull]

Koos Zevenhoven writes:
 > On Tue, Apr 19, 2016 at 2:55 PM, Stephen J. Turnbull <stephen at xemacs.org> wrote:
 > >
 > > AFAICS bytes return from __fspath__ is just YAGNI.  Show me something
 > > that actually wants it.
 > 
 > It might be,

May I take that as meaning you just jumped to the conclusion that
extending polymorphism is useful on no actual evidence of usefulness?

 > but as long as bytes paths are supported polymorphicly all over the
 > stdlib, we won't get rid of supporting bytes paths. So are you
 > proposing to deprecate bytes paths?

You claim "almost always want str", Ethan claims "bias against bytes."
Sorry, guys, you can't have it both ways.  Either bytes paths are
discouraged (not "deprecated", not yet), or they aren't.

I say, let's not encourage them.  Ie, keep the status quo for bytes,
and make things better for the preferred str.  Yes, that means
discouraging bytes relative to str in this context.  That's a Python 3
principle, one strong enough to justify the huge compatibility break
involved in making str be Unicode.  That compatibility break has been
extremely successful in my personal experience as a sometime Python
teacher and Mailman developer, though the Mercurial developers have a
different POV.