gh-116241: Add support of multiple inheritance with typing.NamedTuple by serhiy-storchaka · Pull Request #31781 · python/cpython

serhiy-storchaka · 2022-03-09T10:16:05Z

https://bugs.python.org/issue43923

Issue: NamedTuple can't inherit from another class #116241

JelleZijlstra

I think this goes too far because it's not realistic to expect type checkers to support arbitrary base classes on NamedTuple. Also, there haven't been any user requests that I can see for multiple inheritance with anything other than Generic. So I'd prefer to merge the other PR that allows multiple inheritance with Generic only.

AlexWaygood · 2022-04-29T03:50:02Z

I think this goes too far because it's not realistic to expect type checkers to support arbitrary base classes on NamedTuple. Also, there haven't been any user requests that I can see for multiple inheritance with anything other than Generic. So I'd prefer to merge the other PR that allows multiple inheritance with Generic only.

I also think it makes sense to only allow multiple inheritance with Generic, for now. It's a smaller change; and, there should be opportunity to rethink it in the future if it turns out that people really need arbitrary multiple inheritance for whatever reason.

gvanrossum · 2022-04-30T04:22:10Z

So, let's just close this?

Jason-Y-Z

people really need arbitrary multiple inheritance for whatever reason

Thanks for reopening! This looks like the case now indeed

CoolCat467

Looks great! I ended up doing nearly exactly the same thing in some code of my own to get around this limitation.

Doc/library/typing.rst

Doc/whatsnew/3.13.rst

Misc/NEWS.d/next/Library/2022-04-28-18-45-58.gh-issue-116241.hu9kRk.rst

Doc/library/typing.rst

serhiy-storchaka · 2024-10-09T16:36:57Z

Thank you @AlexWaygood and @gvanrossum. Updated to 3.14 and applied the suggestions.

AlexWaygood

Given that we've had multiple requests for this, I'm okay with landing it. But please get sign-offs from @gvanrossum and @JelleZijlstra before merging.

gvanrossum

Let's do it! (I approve of the idea, I haven't carefully reviewed the code.)

JelleZijlstra · 2024-10-09T18:41:19Z

I'm OK with this given the discussion on the issue; will take another look at the code soon.

hugovk · 2025-04-23T16:38:42Z

Reminder for this: the 3.14 beta freeze is in two weeks.

picnixz

That'd be great to have. I needed this more than once!

picnixz · 2025-05-08T13:22:47Z

Doc/library/typing.rst

      disallowed in Python 3.15. To create a NamedTuple class with 0 fields,
      use ``class NT(NamedTuple): pass`` or ``NT = NamedTuple("NT", [])``.

+   .. versionchanged:: 3.14


Suggested change

.. versionchanged:: 3.14

.. versionchanged:: next

picnixz · 2025-05-08T13:25:50Z

Lib/test/test_typing.py

+        self.assertEqual(a.y, 5)
+        self.assertEqual(len(a), 1)
+
+        class Y(A, NamedTuple):


Maybe add a test to check the order of the members as well when doing unpacking? And maybe test class Z(X, Y, NamedTuple)? (I don't know if this leads to a MRO incompatibilty though)

It will be error. This is tested in the next test.

github-actions · 2026-04-10T12:15:27Z

This PR is stale because it has been open for 30 days with no activity.

johnslavik · 2026-04-10T17:11:00Z

Lib/typing.py

-        for base in bases:
-            if base is not _NamedTuple and base is not Generic:
-                raise TypeError(
-                    'can only inherit from a NamedTuple type and Generic')


Please consider addressing https://gist.github.com/johnslavik/4d0e22df6cb61868f74269fe7d401f5b.

serhiy-storchaka added the type-feature A feature request or enhancement label Mar 9, 2022

bedevere-bot added the awaiting core review label Mar 9, 2022

the-knights-who-say-ni added the CLA signed label Mar 9, 2022

JelleZijlstra mentioned this pull request Mar 10, 2022

bpo-43923: Allow NamedTuple multiple inheritance #31779

Closed

AlexWaygood added the topic-typing label Apr 13, 2022

FHTMitchell mannequin mentioned this pull request Apr 28, 2022

Can't create generic NamedTuple as of py3.9 #88089

Closed

serhiy-storchaka added 2 commits April 28, 2022 19:33

bpo-43923: Add support of generic typing.NamedTuple

939d5f0

bpo-43923: Add support of multiple inheritance with typing.NamedTuple

64f0c5f

serhiy-storchaka force-pushed the typing-namedtuple-multiple-inheritance branch from 637bdd3 to 64f0c5f Compare April 28, 2022 16:48

serhiy-storchaka marked this pull request as ready for review April 28, 2022 17:18

serhiy-storchaka requested review from Fidget-Spinner, JelleZijlstra and gvanrossum as code owners April 28, 2022 17:18

JelleZijlstra reviewed Apr 29, 2022

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serhiy-storchaka closed this Apr 30, 2022

serhiy-storchaka mentioned this pull request Mar 2, 2024

NamedTuple can't inherit from another class #116241

Open

serhiy-storchaka changed the title ~~bpo-43923: Add support of multiple inheritance with typing.NamedTuple~~ gh-116241: Add support of multiple inheritance with typing.NamedTuple Mar 2, 2024

serhiy-storchaka reopened this Mar 2, 2024

serhiy-storchaka requested a review from AlexWaygood as a code owner March 2, 2024 16:01

Merge branch 'main' into typing-namedtuple-multiple-inheritance

d4bc711

serhiy-storchaka force-pushed the typing-namedtuple-multiple-inheritance branch from 5077333 to d4bc711 Compare March 2, 2024 16:09

Jason-Y-Z approved these changes Mar 4, 2024

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CoolCat467 approved these changes Oct 9, 2024

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Fidget-Spinner removed their request for review October 9, 2024 14:36

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serhiy-storchaka added 2 commits October 9, 2024 19:22

Merge branch 'main' into typing-namedtuple-multiple-inheritance

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Address review comments.

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JelleZijlstra self-requested a review October 9, 2024 18:41

Merge branch 'main' into typing-namedtuple-multiple-inheritance

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picnixz reviewed May 8, 2025

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serhiy-storchaka added 2 commits April 10, 2026 17:48

Merge branch 'main' into typing-namedtuple-multiple-inheritance

e44773c

Add also tests for unpacking.

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serhiy-storchaka requested a review from AA-Turner as a code owner April 10, 2026 15:03

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