Type hint for a dict gives TypeError: 'type' object is not subscriptable

If you're using python 3.8, then perhaps you need to do some import from typing import Dict memo: Dict[int, int] = {0: 0, 1: 1} If you're using python 3.9 and above, you should be good. If you're going to do some type hinting. memo: dict[int, int] = {0: 0, 1: 1}