How can I check whether one type is derived from another (python typing module)

Question

For instance, I want

from typing import Dict, List
check_derived(Dict[int, int], Dict) == True
check_derived(List[str], List) == True
check_derived(List, Dict) == False

and so on.

Do I have to write my own mapping of derived classes to classes in order to achieve this? Seems hacky.

Possible duplicate of [List all base classes in a hierarchy of given class?](https://stackoverflow.com/questions/1401661/list-all-base-classes-in-a-hierarchy-of-given-class) — Green Cloak Guy, Oct 28 '19 at 20:56
Like this, I will say that is not usefull as Dict[x, x] is a Dict what ever are inside. Are you looking for `isinstance`? — Florian Bernard, Oct 28 '19 at 20:57

Cory Nezin · Answer 1 · 2019-10-28T21:18:29.447

Thanks @Green Clock Guy, that seems to have worked!

import inspect
from typing import Dict, List

def check_derived(left, right):
  """True if left derived from right"""
  left_classes = inspect.getmro(left)
  return right in left_classes

assert check_derived(Dict[int, int], Dict) == True
assert check_derived(List[str], List) == True
assert check_derived(List, Dict) == False

Edit: However I see that this fails for the case

assert check_derived(Union[str, int], int) == True

How can I check whether one type is derived from another (python typing module)

1 Answers1