Alas, MyPy doesn't have the concept of "keyof" and mapped types like TypeScript. So in place of that I would: 1. Define a variable called Params = Any; 2. Li

Alas, MyPy doesn't have the concept of "keyof" and mapped types like TypeScript. So in place of that I would: 1. Define a variable called Params = Any; 2. Liberally use Param["foo"] and Param["bar"] anywhere. 3. Once you stabilize, reimplement Params as a TypedDict. You'll get failures if accessing any invalid key. You can also use a NamedTuple if you prefer. If you insist passing a param name, then you'll have to create a big list of Literals for param with every key in your dict. So Param = Literal["foo", "bar"] etc.