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

Koos Zevenhoven k7hoven at gmail.com
Wed Apr 20 06:19:50 EDT 2016 
On Wed, Apr 20, 2016 at 6:16 AM, Stephen J. Turnbull <stephen at xemacs.org> wrote:
>
> (1) some really attractive producer of pathlib.Paths will be
>     published, and
>

Yes, pathlib is str-only, so this sounds just right.

> (2) people will want to plug that producer into their bytes paths
>     consumers using os.fspath(path) "and be done with it".
>

No, fspath can't know that is the the right thing to do.  There should
be *someone* that is aware of the encoding that happens, either the
provider or the consumer. That byte path consumer, assuming it wants
to support the behavior you describe, should use os.fsencode instead
of os.fspath, which will do exactly what you want, and just as easy
for the bytes path consumer to implement!

(Unless you want to explicitly reject plain str objects, which you
would then indeed do *explicitly*, but I'm not sure there is a point
in accepting plain bytes and str-based pathlib objects but not str).

To avoid further unnecessary discussion, please read [1] carefully,
where I already explained this, among other things.

-Koos

[1] https://mail.python.org/pipermail/python-dev/2016-April/144239.html
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