Undeprecate typing.Callable and deprecate collections.abc.Callable

[nathanielmanistaatgoogle]

Feature or enhancement

Proposal:

Callable doesn't seem to have much "idea overlap" with Collection - Callables don't deal with zero-or-more of a thing, or whether or not a thing appears among another population of things, or any of the other concerns that give conceptual coherence to Collection and the rest of the family (Set, Mapping, Sequence and so forth) in collections.abc.

Also old-issue-tracker issue 27598 seems to be the scope for the change that introduced Callable to collections.abc, but it doesn't give any insight into why Callable was included.

What might I be overlooking that would motivate a reason for Callable to "belong" in collections.abc?

If there's no particular reason for Callable to be in collections.abc, might typing.Callable be un-deprecated? And might collections.abc.Callable be deprecated?

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

[ZeroIntensity]

As far as I know, this has been brought up before, and not just for Callable--types like Coroutine, Generator, and some others are also not necessarily "collections." I'm not sure what the consensus was, but I suspect the motivation for keeping them in collections.abc is to keep all the types in the same place.

[picnixz]

Many linters mark typing.* aliases as replaceable by collections.abc.* and I believe this is the right course of action. Any project that updated according to those recommendations would then need to revert this :/

Note that importing typing is usually heavier than importing collections.abc so there is also some benefits not to import typing.

Also, I think we've been deprecating it since 3.9 but we don't have a removal version yet (so they are just deprecated but they still work as they should).

I would advise closing this issue and open a DPO thread (or find one that is about it) since this doesn't seem a simple feature request.

And yes, I also think we wanted to keep protocol-like and base ABCs classes in one place (a shame we didn't have a top-level module like "interfaces.py" to gather them there).

cc @JelleZijlstra

[hauntsaninja]

We're not going to remove typing.Callable. If it makes you happy, use it.

[gvanrossum]

But then why deprecate it at all? Why not have two equivalent names? Sometimes importing it from typing is free (if you’re using other things from there anyways) while collections.abc costs extra. Sometimes the Zen is not worth sticking to.

[hauntsaninja]

It's a fair question!

If OP or anyone else would like to pursue undeprecation, picnixz's suggestion of starting a discuss.python.org thread sounds like the right first move.

For me personally:
The SC signed off on the deprecations in PEP 585 (at a time before I felt confident contributing to typing discussions). Rather than relitigate, I've chosen so far to just focus on not breaking people (e.g. https://github.com/python/peps/pull/2778/files). Sometimes these threads go round in circles and I don't currently have the patience to take that on, given that the main current cost is a note in the docs.

[sobolevn]

I feel like collections.abc.* types have better runtime semantics, unlike Python-based typing.* aliases. To me - this is the main point of using them instead of older typing ones.

[JelleZijlstra]

I feel similarly to Shantanu; I think actually removing the typing.* versions would be very disruptive for little gain.

[gvanrossum]

Maybe we could do the following. Make it clear in the docs that the removal must be a Typing Council decision and remove the explicit end date, since that is too soon for comfort.