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Inconsistent TypeError messages with callables #136327
Description
Bug report
Bug description:
Consider this example:
>>> class A:
... def __str__(self): return "some random text"
... def __call__(self, a): ...
>>> A()()
Traceback (most recent call last):
File "<python-input-16>", line 1, in <module>
A()()
~~~^^
TypeError: A.__call__() missing 1 required positional argument: 'a'
>>> A()(*None)
Traceback (most recent call last):
File "<python-input-17>", line 1, in <module>
A()(*None)
~~~^^^^^^^
TypeError: some random text argument after * must be an iterable, not NoneTypeThe first one gets the callable's __qualname__. The second, on the other hand, does not, but should do so.
Another example, mentioned in #135975 (issuecomment link):
>>> exit(*None)
Traceback (most recent call last):
File "<python-input-0>", line 1, in <module>
exit(*None)
~~~~^^^^^^^
TypeError: Use exit() or Ctrl-Z plus Return to exit argument after * must be an iterable, not NoneTypeWhich just gets the exit's __repr__.
If this is recognized as unwanted behaviour, I'm ready to make a PR.
CPython versions tested on:
3.13
Operating systems tested on:
Windows
Edit: ** also does not work properly:
# the code from the first example
>>> A()(**1)
Traceback (most recent call last):
File "<python-input-26>", line 1, in <module>
A()(**1)
~~~^^^^^
TypeError: some random text argument after ** must be a mapping, not int
Activity
pythongh-136327: Harmonize arg types for incompatibel types after `*`…
sobolevn commentedon Jul 6, 2025
Please, go ahead :)
I would love to review it!
Tapeline commentedon Jul 7, 2025
I've done some investigation on this bug. Seems that it's harder, than I initially thought.
The function's name is received via
_PyObject_FunctionStr, which indeed gets the function's qualname. If the qualname isn't present, it just gets whatever is in__str__/__repr__of the function.Regarding the examples I've shown earlier:
exitis behaving this way, because some objects in__builtins__for some reason do not have the__qualname__attribute. Here's the full list:I'm not quite sure about the dunder ones, but all others definetly should have a qualname.
_PyObject_FunctionStr. Since it does not have a__qualname__, it defaults to whatever is in__str__/__repr__of that object. Possible solution would be to just add an edge-case handler to_PyObject_FunctionStr: if an object is not an instance offunctionorbuiltin_function_or_method, then we try searching inobject.__call__.Merge branch 'refs/heads/main' into fix-pythongh-136327
gh-136327: Fix inconsistent ``TypeError`` messages regarding invalid …
pythongh-136327: Fix inconsistent ``TypeError`` messages regarding in…