Basically a distilled down version of this (as yet unanswered) question. I want to state that a variable should only take on values that are keys in a TypedDict. At present I'm defining a separate Literal type to represent the keys, for example: from typing import Literal, TypedDict class MyTD(TypedDict): a: int b: int mytd = MyTD(a=1, b=2) key = "a" mytd[key] # error: TypedDict key must be a string literal; expected one of ('a', 'b') MyTDKeyT = Literal["a", "b"] typed_key: MyTDKeyT = "b" mytd[typed_key] # no error I would like to be able to replace the Literal definition for all the usual reasons of wanting to minimize duplicated code. Pseudo-code: key: Keys[MyTD] = "a" mytd[key] # would be no error not_key: Keys[MyTD] = "z" # error Is there a way to achieve this? To clarify, given that mypy can tell me that the key type needs to be a literal of "a" or "b", I'm hoping there might be a less error prone way to annotate a variable to that type, rather than having to maintain two separate lists of keys side-by-side, once in the TypedDict definition, once in the Literal definition. Continue reading...
