[aribaskagan]

Fixes #77371.

help(types.new_class) only said "Create a class object dynamically using the appropriate metaclass." Callers coming from type(name, bases, dict) were treating kwds as that namespace. As discussed on the issue, kwds is the keywords of the class statement, and the body is filled in by exec_body. Doc/library/types.rst already says this, so it is unchanged. prepare_class() gets the same one-sentence note.

Before:

Create a class object dynamically using the appropriate metaclass.

After:

Create a class object dynamically using the appropriate metaclass.

*name*, *bases*, and *kwds* are the class name, the base classes,
and the keywords of the equivalent class definition (such as
'metaclass').  *kwds* is not a namespace like the third argument
of type().  For example:

    new_class('Test', (A, B), {'metaclass': Meta, 'foo': 42})

is equivalent to:

    class Test(A, B, metaclass=Meta, foo=42):
        pass

To populate the namespace, pass *exec_body*, a callable that takes
the newly created dictionary and populates it.  For example:

    new_class('C', (MyABC,), {},
              exec_body=lambda ns: ns.update(namespace))

AI assistance was used in preparing this change; I reviewed and tested it.

• Issue: problem with ABCMeta.__prepare__ when called after types.new_class #77371

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[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-12T17:50:55.047307Z	adf3991	PR opened

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[chatgpt-codex-connector]

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Reviewed commit: adf39919c7

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[chatgpt-codex-connector]

Describe exec_body's argument as a namespace mapping

With a metaclass whose __prepare__ returns a valid non-dict mapping, prepare_class() returns that object and new_class() passes it to exec_body; a mapping need not implement dictionary methods such as .update(), so calling it a “dictionary” can mislead callbacks that use dict-only methods, and the example immediately below uses .update(). Please use “prepared namespace” or “mapping,” as Doc/library/types.rst does.

AGENTS.md reference: AGENTS.md:L14-L14

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