[Python-Dev] file system path protocol PEP

[Sven R. Kunze]

On 11.05.2016 23:57, Brett Cannon wrote:
> On Wed, 11 May 2016 at 14:29 Nikolaus Rath <Nikolaus at rath.org 
> <mailto:Nikolaus at rath.org>> wrote:
>
>     On May 11 2016, Brett Cannon <brett at python.org
>     <mailto:brett at python.org>> wrote:
>     > This PEP proposes a protocol for classes which represent a file
>     system
>     > path to be able to provide a ``str`` or ``bytes`` representation.
>     [...]
>
>     As I said before, to me this seems like a lot of effort for a very
>     specific use-case.
>

Exactly. Especially when considering what else can be done to improve 
the situation considerably.

>     So let me put forward two hypothetical scenarios to
>     better understand your position:
>
>     - A new module for URL handling is added to the standard library (or
>       urllib is suitably extended). There is a proposal to add a new
>       protocol that allows classes to provide a ``str`` or ``bytes``
>       representation of URLs.
>
>     - A new (third-party) library for natural language processing arises
>       that exposes a specific class for representing audio data. Existing
>       language processing code just uses bytes objects. To ease transition
>       and interoperability, it is proposed to add a new protocol for
>     classes
>       that represend audio data to provide a bytes representation.
>

You can even add the timedelta-to-seconds protocol that somebody thought 
would be good idea:

https://mail.python.org/pipermail/python-dev/2016-April/144018.html
https://mail.python.org/pipermail/python-ideas/2016-May/040226.html

The generalization is straight-forward and a result of this discussion. 
If it works and is a good idea for pathlib, then there's absolutely no 
reason not to do this for the datetime lib and other rich-object libs. 
Same goes the other way round. Question still is: is it a good idea?

Maybe, it will become a successful pattern. Maybe not.

>     Do you think you would you be in favor of adding these protocols to
>     the stdlib/languange reference as well?
>
>
> Maybe for URLs, not for audio data (at least not in the stdlib; 
> community can do what they want).
>
>     If not, what's the crucial
>     difference to file system paths?
>
>
> Nearly everyone uses file system paths on a regular basis, less so 
> than URLs but still a good amount of people. Very few people work with 
> audio data.

Amount of usage should be taken into account of course. However, 
question remains if that suffices as a justification for the effort.


Best,
Sven
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