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 <p...@hb9etc.ch
<mailto:p...@hb9etc.ch>> 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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