bpo-46998: Allow subclassing Any at runtime by hauntsaninja · Pull Request #31841 · python/cpython ·

https://bugs.python.org/issue46998

This PR also permits issubclass(X, Any). I don't actually have a use case for doing so, so happy to forbid it if people feel strongly.

The error in functools.singledis used to be TypeError: Invalid annotation for 'x'. typing.Any is not a class.. Since typing.Any is now a class, that isn't quite true. We could add a special case check in singledis against typing.Any if we think it's important to prevent its use. The dedicated tests for Any were added very recently, in #30050

Lib/test/test_typing.py

Lib/typing.py

Misc/NEWS.d/next/Library/2022-03-13-08-52-58.bpo-46998.cHh-9O.rst

JelleZijlstra · 2022-03-13T20:26:29Z

Lib/test/test_functools.py

@@ -2802,8 +2802,6 @@ def f(arg):
 f.register(list[int] | str, lambda arg: "types.UnionTypes(types.GenericAlias)")
 with self.assertRaisesRegex(TypeError, "Invalid first argument to "):
 f.register(typing.List[float] | bytes, lambda arg: "typing.Union[typing.GenericAlias]")
-with self.assertRaisesRegex(TypeError, "Invalid first argument to "):
-f.register(typing.Any, lambda arg: "typing.Any")


This might be worth forbidding explicitly because the behavior could be quite unintuitive. Happy to leave that decision to the functools maintainer though.

@ambv, do you have any thoughts on the bits of this PR that touch singledis?

JelleZijlstra · 2022-03-13T20:27:34Z

Lib/typing.py

-@_SpecialForm
-def Any(self, parameters):
+class _AnyMeta(type):
+def __instancecheck__(self, obj):


Should we even have this? isinstance(X, Any) is now a meaningful operation.

I'm fine with removing it (as this PR currently does for issubclass). Doing so would also allow us to get rid of the metaclass, which will help remove restrictions on what classes can inherit from Any.
My reasoning for keeping it is that isinstance is very commonly used, potentially by typing / Python novices, and isinstance(..., Any) doesn't correspond well to the notion of Any at type check time. Sophisticated users have workarounds available to them for the equivalent isinstance check.

Lib/typing.py

JelleZijlstra · 2022-03-13T20:28:52Z

Lib/typing.py

@@ -428,8 +428,15 @@ def __getitem__(self, parameters):
 return self._getitem(self, *parameters)


-@_SpecialForm
-def Any(self, parameters):
+class _AnyMeta(type):


The metaclass is unfortunate because it restricts what classes can double-inherit from Any (due to metaclass conflicts). Seems unavoidable though.

Not entirely unavoidable, if we were willing to give up on instancecheck (and repr), I'd say we could just remove the metaclass entirely

Co-authored-by: Jelle Zijlstra <[email protected]>

Planning to merge in a few days unless there's more discussion.

Looking at it again, I realize we should document this. Probably fine to just add a note like .. versionchanged: 3.11: Any can now be used as a base class.

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

And if you don't make the requested changes, you will be poked with soft cushions!

@JelleZijlstra

Thanks for making the requested changes!

@JelleZijlstra: please review the changes made to this pull request.

merwok · 2022-03-30T12:53:30Z

Doc/library/typing.rst

@@ -578,6 +578,9 @@ These can be used as types in annotations and do not support ``[]``.
 * Every type is compatible with :data:`Any`.
 * :data:`Any` is compatible with every type.

+.. versionchanged:: 3.11
+:data:`Any` can now be used as a base class


Can you add some explanation about the use cases?
This doesn’t say why someone could want that, nor does the ticket, one has to hunt for the last message in the mailing list thread!

I added a sentence here. Let me know if I should make it longer; I tried to keep it short because this is a lot more niche than other things covered in typing.rst

I think adding one short example might be nice

Not sure about this. On the one hand an example would be useful; on the other hand it risks putting too much emphasis on a pretty obscure use case.

Let's omit the example then (devguide says "err on the side of being succinct" for docs). I'm hoping to do some work on typing docs sometime soon, which might be a better home for such details.

@Gobot1234

https://build.opensuse.org/request/show/1031001 by user mcepl + dimstar_suse - Clean specfile from old cruft. - Requires Python 3.7+ - Fix testsuite: Must test as module; don't need multibuild. - Update Summary and Description - Update to version 4.4.0 * Add `typing_extensions.Any` a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike `default` parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding `typing_extensions.override`. by Jelle Zijlstra. * Add the `infer_variance` parameter to `TypeVar`, as specified in PEP 695. by Jelle Zijlstra.

@Gobot1234

https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. (From OE-Core rev: 0b8f212744f8de7e6b33ab02d042009eba462241) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>

@Gobot1234

https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. (From OE-Core rev: 0b8f212744f8de7e6b33ab02d042009eba462241) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>

@Gobot1234

https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. (From OE-Core rev: 34c8f1eac66ae770d64eaa854b1f263848210773) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. License-Update: update copyright years; align with CPython LICENSE See python/typing_extensions#63 (From OE-Core rev: 6dc6c11b638c1d45f4dc9c7813f93a09229c33b3) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. License-Update: update copyright years; align with CPython LICENSE See python/typing_extensions#63 (From OE-Core rev: 0cb15457edaa6cee3ac152a18d8b6ba4204dd958) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. License-Update: update copyright years; align with CPython LICENSE See python/typing_extensions#63 (From OE-Core rev: 0cb15457edaa6cee3ac152a18d8b6ba4204dd958) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. License-Update: update copyright years; align with CPython LICENSE See python/typing_extensions#63 (From OE-Core rev: 15ca091ae01ae298c013e8cf82ee6af382259ed8) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]> Signed-off-by: Richard Purdie <[email protected]>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. License-Update: update copyright years; align with CPython LICENSE See python/typing_extensions#63 Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>

@Gobot1234

…thon-3.10.8 - Updated from version 4.1.1 to 4.4.0 - Update of rootfile - Changelog # Release 4.4.0 (October 6, 2022) - Add `typing_extensions.Any` a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). - Add initial support for TypeVarLike `default` parameter, PEP 696. by Marc Mueller (@cdce8p). - Runtime support for PEP 698, adding `typing_extensions.override`. by Jelle Zijlstra. - Add the `infer_variance` parameter to `TypeVar`, as specified in PEP 695. by Jelle Zijlstra. # Release 4.3.0 (July 1, 2022) - Add `typing_extensions.NamedTuple`, allowing for generic `NamedTuple`s on Python <3.11 (backport from python/cpython#92027, by Serhiy Storchaka). by Alex Waygood (@AlexWaygood). - Adjust `typing_extensions.TypedDict` to allow for generic `TypedDict`s on Python <3.11 (backport from python/cpython#27663, by Samodya Abey). by Alex Waygood (@AlexWaygood). # Release 4.2.0 (April 17, 2022) - Re-export `typing.Unpack` and `typing.TypeVarTuple` on Python 3.11. - Add `ParamSpecArgs` and `ParamSpecKwargs` to `__all__`. - Improve "accepts only single type" error messages. - Improve the distributed package. by Marc Mueller (@cdce8p). - Update `typing_extensions.dataclass_transform` to rename the `field_descriptors` parameter to `field_specifiers` and accept arbitrary keyword arguments. - Add `typing_extensions.get_overloads` and `typing_extensions.clear_overloads`, and add registry support to `typing_extensions.overload`. Backport from python/cpython#89263. - Add `typing_extensions.assert_type`. Backport from bpo-46480. - Drop support for Python 3.6. Original by Adam Turner (@AA-Turner). Tested-by: Adolf Belka <[email protected]> Signed-off-by: Adolf Belka <[email protected]>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://.com/python/typing_extensions/blob/main/CHANGELOG.md#release-440-october-6-2022 Release 4.4.0 (October 6, 2022) * Add typing_extensions.Any a backport of python 3.11's Any class which is subclassable at runtime. (backport from python/cpython#31841, by Shantanu and Jelle Zijlstra). by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. by Jelle Zijlstra. License-Update: update copyright years; align with CPython LICENSE See python/typing_extensions#63 (From OE-Core rev: 15ca091ae01ae298c013e8cf82ee6af382259ed8) Signed-off-by: Tim Orling <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]> Signed-off-by: Richard Purdie <[email protected]>

bpo-46998: Allow subclassing Any at runtime

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bedevere-bot added the awaiting review label Mar 13, 2022

the-knights-who-say-ni added the CLA signed label Mar 13, 2022

hauntsaninja added 2 commits March 12, 2022 19:10

make error consistent

abea39a

remove functools checks

771f492

📜🤖 Added by blurb_it.

900f2c7

hauntsaninja marked this pull request as ready for review March 13, 2022 08:54

hauntsaninja requested review from gvanrossum, Fidget-Spinner, JelleZijlstra and rhettinger as code owners March 13, 2022 08:54

JelleZijlstra reviewed Mar 13, 2022
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hauntsaninja and others added 6 commits March 13, 2022 14:38

more tests

6e76441

Update Misc/NEWS.d/next/Library/2022-03-13-08-52-58.bpo-46998.cHh-9O.rst

b00ab17
Co-authored-by: Jelle Zijlstra <[email protected]>

oops, fix test

4d913ad

cooperative inheritance

1c1ab38

fix tests

4927e78

okay, make instancecheck work with multiple inheritance

68ea3a8

hauntsaninja requested a review from JelleZijlstra March 23, 2022 06:24

JelleZijlstra approved these changes Mar 24, 2022
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JelleZijlstra self-assigned this Mar 24, 2022

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mention in docs

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bedevere-bot requested a review from JelleZijlstra March 30, 2022 02:35

hauntsaninja added 2 commits March 29, 2022 22:08

Merge remote-tracking branch 'upstream/main' into subclass-any

05db029

fix pydoc test

e11f405

merwok reviewed Mar 30, 2022
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hauntsaninja added 2 commits March 30, 2022 14:54

add a sentence on reasoning

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preposition

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JelleZijlstra approved these changes Apr 1, 2022
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JelleZijlstra merged commit 5a4973e into python:main Apr 5, 2022

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JelleZijlstra mentioned this pull request Apr 13, 2022
Add typing to 3.11 What's New #91491
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hauntsaninja deleted the subclass-any branch April 26, 2022 03:09

sobolevn mentioned this pull request Aug 30, 2022
gh-95987: Fix repr of Any type subclasses #96412
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mikelane mentioned this pull request Oct 7, 2022
Bump typing-extensions from 4.3.0 to 4.4.0 mikelane/reddit-get#82
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hauntsaninja mentioned this pull request Aug 1, 2023
Allow subclassing Any at runtime #91154
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