I've written this code: from typing import overload, TYPE_CHECKING, Protocol, Any import pyarrow as pa # type: ignore[import-not-found] class PyArrowArray(Protocol): @property def buffers(self) -> Any: ... @overload def func(a: PyArrowArray) -> int: ... @overload def func(a: str) -> str: ... @overload def func(a: Any) -> str | int: ... def func(a) -> str | int: if isinstance(a, pa.Array): return 0 return '0' reveal_type(func(pa.array([1,2,3]))) PyArrow is a Python library which does not have type hints. However, there is a package pyarrow-stubs which provides types for it. I have a function can accept either a pyarrow.Array or a str: if it receives a pyarrow.Array, it returns an int if it receives a str, it returns a str I would like to annotate it such that: if a user has pyarrow-stubs installed, then func(pa.array([1,2,3])) is revealed to be int if a user doesn't have pyarrow-stubs installed, then func(pa.array([1,2,3])) should be revealed to be int | str, because pa is not known statically I was hoping that the code above would accomplish that, but it doesn't. If pyarrow-stubs is not installed, I get Revealed type is "Any" I was expecting that the @overload def func(a: Any) -> str | int: ... overload would be matched and that I'd get Revealed type is int | str Continue reading...
