I need to type-hint that a value is either some TypedDict or a completely empty dict. The TypedDict itself already exists and is non-trivial, and it's an all-or-nothing situation – so modifying the TypedDict to have optional keys is not sufficient. How can I type-hint the "completely empty dict" part for use in a union or similar? Since I already use TypedDict, defining an empty TypedDict seems natural. However, neither MyPy nor PyRight meaningfully accept this: the resulting type cannot actually be used even as a trivial Mapping. from typing import TypedDict, Mapping class EmptyDict(TypedDict): pass def foo(bar: Mapping[str, float]) -> None:... foo(EmptyDict()) MyPy rejects this with: error: Argument 1 to "foo" has incompatible type "EmptyDict"; expected "Mapping[str, float]" [arg-type] PyRight rejects this with: Argument of type "EmptyDict" cannot be assigned to parameter "bar" of type "Mapping[str, float]" in function "foo" "EmptyDict" is not assignable to "Mapping[str, float]" Type parameter "_VT_co@Mapping" is covariant, but "object" is not a subtype of "float" "object" is not assignable to "float" (reportArgumentType) Continue reading...
