Re: PEP 505 (None-aware operators) for Python 3.11

On 19. 09. 22 17:58, Guido van Rossum wrote:
> Personally I think returning None is a fine API design, and IMO the 
> concerns about this pattern are overblown. Note that X|None is no 
> different than the "Maybe X" pattern that functional programmers are so 
> fond of.

I must disagree here. With `X|None` there is no way to do 
`Maybe[Maybe[X]]`, and FP is all about proper composition.

One practical consequence is that "Maybe X" doesn't have the problem 
that PEP 661 (Sentinel Values) tries to solve.


> On Mon, Sep 19, 2022 at 8:02 AM Philipp Burch <[email protected] 
> <mailto:[email protected]>> wrote:
> 
>     Hi all,
> 
>     I've only here found out that there is a discussion going on about
>     those
>     none-aware operators and my first thought was "great, finally!". FWIW,
>     I'd be happy with the syntax suggestion in the PEP, since '?' looks
>     rather intuitive to me to mean something like "maybe".
> 
>     However, I then read the mentioned post of Steve Dower, with the final
>     summary:
> 
>       > So to summarise my core concern - allowing an API designer to "just
>     use None" is a cop out, and it lets people write lazy/bad APIs rather
>     than coming up with good ones.
> 
>     This is a very good point. In fact, I've never really thought about it
>     that way and of course he's totally right that "SomeType | None" (or
>     Optional[SomeType], which also somehow made me feel that this usage is
>     fairly intended) is not optimal, at least for user defined
>     types/classes. The problem is, that I never actually thought about his
>     suggested way. And I wouldn't be surprised if this holds for many other
>     people as well.
> 
>     Maybe it would be great to boldly mention these thoughts in the
>     documentation at an appropriate place. In my opinion, there are at
>     least
>     the following good places where this would fit nicely:
> 
>     - The documentation of the dataclasses
>     (https://docs.python.org/3/library/dataclasses.html
>     <https://docs.python.org/3/library/dataclasses.html>), since this is
>     probably the most common use case for the "| None" pattern. Going
>     further, the dataclasses functionality might even be extended to
>     make it
>     simpler to generate such null-types (or however they are called), so
>     that it is no longer "a tonne more work".
> 
>     - Linters like pylint could emit a note when seeing the "| None"
>     pattern, linking to the explanation about why it is possibly not the
>     best way to do it.
> 
>     - The documentation of the discussed None-aware operators. Since these
>     new operators are closely coupled to the arguably suboptimal "| None"
>     pattern, it is probably good to tell folks right there why they should
>     consider better alternatives.
> 
>     As mentioned, I absolutely see Steve's point. However, there are many
>     Python scripts/programs working without a complex API, where this "|
>     None" pattern may still have its legitimate uses and the none-aware
>     operators can make code easier to read (and write).
> 
>     Best regards,
>     Philipp
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> 
> -- 
> --Guido van Rossum (python.org/~guido <http://python.org/~guido>)
> /Pronouns: he/him //(why is my pronoun here?)/ 
> <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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