On 20. 09. 22 10:59, Petr Viktorin wrote:
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.
Sorry, hit Send too soon: I'm not arguing against returning None being good design. Just the note that compares it to FP's Maybe.
On Mon, Sep 19, 2022 at 8:02 AM Philipp Burch <phip@hb9etc.ch <mailto:phip@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 _______________________________________________ Python-Dev mailing list -- python-dev@python.org <mailto:python-dev@python.org> To unsubscribe send an email to python-dev-leave@python.org <mailto:python-dev-leave@python.org> https://mail.python.org/mailman3/lists/python-dev.python.org/ <https://mail.python.org/mailman3/lists/python-dev.python.org/> Message archived at
https://mail.python.org/archives/list/python-dev@python.org/message/Q2MOF5CJ... <https://mail.python.org/archives/list/python-dev@python.org/message/Q2MOF5CJ...> Code of Conduct: http://python.org/psf/codeofconduct/ <http://python.org/psf/codeofconduct/>
-- --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-c...>
_______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/7HEZXSLT... Code of Conduct: http://python.org/psf/codeofconduct/