In typescript, there is a construct called index signature that let me, for instance, express that all properties of a particular object have values of type string, i.e:
type Foo = { [key: string]: string }
How do I type hint something similar in Python, e.g express that all attributes of a class should have values of type string? The reason I want to do this because I have a Python class whose attributes are not known in advance, but are set dynamically.
The equivalent of your Foo type would be a dict with keys and values that both have type str:
Foo = dict[str, str]
If you're generating attributes on a custom class dynamically via __getattr__, the signature of __getattr__ determines the type of the attributes:
class Foo:
def __getattr__(self, name: str) -> str:
return "foo"
f = Foo()
reveal_type(f.bar) # note: Revealed type is "builtins.str"