Pydoc usesinspect.signature() to get a function signature.inspect.signature() supports Python functions, and also extension functions defined with Argument Clinic (by parsing the__text_signature__ attribute). Unfortunately Argument Clinic is used with functions whose signature cannot be expressed in Python, e.g.getattr() ordict.pop(). It produces a human readable__text_signature__, but it can not be represented as aSignature object, soinspect.signature() fails. Pydoc display generic(...) for such functions.

Since pydoc only needs a string representation of signature, not aSignature object, I propose to use__text_signature__ ifinspect.signature() fails. It needs only some trivial processing.

Before:

getattr(...)    Get a named attribute from an object.    getattr(x, 'y') is equivalent to x.y    When a default argument is given, it is returned when the attribute doesn't    exist; without it, an exception is raised in that case.

After:

getattr(object, name, default=<unrepresentable>, /)    Get a named attribute from an object.    getattr(x, 'y') is equivalent to x.y    When a default argument is given, it is returned when the attribute doesn't    exist; without it, an exception is raised in that case.

Linked PRs

• gh-107782: Pydoc: fall back to __text_signature__ if inspect.signature() fails #107786
• gh-107782: Use _testcapi to test non-representable signatures #109325