bpo-46998: Allow subclassing Any at runtime #31841

hauntsaninja · 2022-03-13T03:07:23Z

https://bugs.python.org/issue46998

hauntsaninja · 2022-03-13T08:48:53Z

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.singledispatch 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 singledispatch 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 singledispatch?

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 <jelle.zijlstra@gmail.com>

JelleZijlstra · 2022-03-29T23:13:48Z

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

JelleZijlstra

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.

bedevere-bot · 2022-03-29T23:28:55Z

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.

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hauntsaninja · 2022-03-30T02:35:29Z

a comment on this pull request containing the phrase I have made the requested changes; please review again

bedevere-bot · 2022-03-30T02:35:32Z

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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike `default` parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding `typing_extensions.override`. Patch by Jelle Zijlstra. * Add the `infer_variance` parameter to `TypeVar`, as specified in PEP 695. Patch by Jelle Zijlstra.

@Gobot1234

https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch by Jelle Zijlstra. (From OE-Core rev: 0b8f212744f8de7e6b33ab02d042009eba462241) Signed-off-by: Tim Orling <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

@Gobot1234

https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch by Jelle Zijlstra. (From OE-Core rev: 0b8f212744f8de7e6b33ab02d042009eba462241) Signed-off-by: Tim Orling <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

@Gobot1234

https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch by Jelle Zijlstra. (From OE-Core rev: 34c8f1eac66ae770d64eaa854b1f263848210773) Signed-off-by: Tim Orling <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch 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 <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch 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 <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch 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 <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch 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 <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

@Gobot1234

* Add SUMMARY, DESCRIPTION, BUGTRACKER and SECTION * Update HOMEPAGE to agree with PyPi https://github.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). Patch by James Hilton-Balfe (@Gobot1234). * Add initial support for TypeVarLike default parameter, PEP 696. Patch by Marc Mueller (@cdce8p). * Runtime support for PEP 698, adding typing_extensions.override. Patch by Jelle Zijlstra. * Add the infer_variance parameter to TypeVar, as specified in PEP 695. Patch by Jelle Zijlstra. License-Update: update copyright years; align with CPython LICENSE See python/typing_extensions#63 Signed-off-by: Tim Orling <tim.orling@konsulko.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

@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). Patch by James Hilton-Balfe (@Gobot1234). - Add initial support for TypeVarLike `default` parameter, PEP 696. Patch by Marc Mueller (@cdce8p). - Runtime support for PEP 698, adding `typing_extensions.override`. Patch by Jelle Zijlstra. - Add the `infer_variance` parameter to `TypeVar`, as specified in PEP 695. Patch 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). Patch 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). Patch 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. Patch 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 patch by Adam Turner (@AA-Turner). Tested-by: Adolf Belka <adolf.belka@ipfire.org> Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>

bpo-46998: Allow subclassing Any at runtime

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hauntsaninja added 2 commits March 12, 2022 19:10

make error consistent

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remove functools checks

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📜🤖 Added by blurb_it.

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

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

more tests

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

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Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

oops, fix test

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cooperative inheritance

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fix tests

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okay, make instancecheck work with multiple inheritance

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

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mention in docs

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hauntsaninja added 2 commits March 29, 2022 22:08

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

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fix pydoc test

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add a sentence on reasoning

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preposition

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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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sobolevn mentioned this pull request Aug 30, 2022

gh-95987: Fix repr of Any type subclasses #96412

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Bump typing-extensions from 4.3.0 to 4.4.0 mikelane/reddit-get#82

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Allow subclassing Any at runtime #91154

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bpo-46998: Allow subclassing Any at runtime #31841

bpo-46998: Allow subclassing Any at runtime #31841

hauntsaninja commented Mar 13, 2022 •

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bpo-46998: Allow subclassing Any at runtime #31841

bpo-46998: Allow subclassing Any at runtime #31841

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