Why I cannot type a `list` parameter in a class with an existing `list` method

Question

I'm working with Python 3.10 and I have this class (which I have simplified):

class Greetings:
    def list(self) -> list[str]:
        return ['ab', 'cd']

    def hello(self, names: list[str]) -> None:
        for name in names:
            print("Hello", name)

While testing it, I got this error:

... in Greetings
    def hello(self, names: list[str]) -> None:
E   TypeError: 'function' object is not subscriptable` error.

I know that the issue comes from my list method, which Python is trying to use in the typing of the names parameter. But I don't understand why this is happening or if it an issue with Python language. It is suppose that starting with Python 3.10 I can use list as typing instead of importing List from the typing module.

Any guess?

Answer 1

After you define def list, the name list inside your class block refers to that def list method. You've shadowed the name. You can work around this by aliasing list, or by using builtins:

import builtins

class Greetings:
    ...

    def hello(self, names: builtins.list[str]) -> None:
        ...