Python: Get type of `typing.List`

Question

I have annotated the arguments of a function as

import typing

def f(x: typing.List[MyType]):
    ...

By inspecting the parameter arguments, I get for the type of x, an instance of typing.GenericMeta which is, correctly, printed as typing.List[MyType]

How can I get the List and MyType from this object?

Answer 1

If you want to get MyType, you can find it under .__args__:

import typing

def f(x: typing.List[MyType]):
    ...

print(f.__annotations__["x"].__args__[0])  # prints <class '__main__.MyType'>

List (i.e. typing.List) is accessible from .__base__, and the actual list class comes from .__orig_bases__:

print(f.__annotations__["x"].__base__)  # prints typing.List[float]
print(f.__annotations__["x"].__orig_bases__[0])  # prints <class 'list'>