Python: What is the typing.TypeAliasType (Python 3.12)?

1# Python 3.12+ syntax
2type UserID = int
3type JSON = dict[str, any]
4type Handler = Callable[[str, int], bool]
5
6# Usage
7def get_user(user_id: UserID) -> JSON:
8    return {"id": user_id}
9
10def register_handler(handler: Handler) -> None:
11    handlers.append(handler)
12
13# Complex aliases
14type Response[T] = dict[str, T]
15type Result[T, E] = tuple[T | None, E | None]
16
17# Usage with generics
18def process() -> Response[User]:
19    return {"data": User("Alice")}
20
21def divide(a: int, b: int) -> Result[int, str]:
22    if b == 0:
23        return (None, "Division by zero")
24    return (a // b, None)
25
26# Pre-3.12 equivalent
27from typing import TypeAlias
28
29UserID: TypeAlias = int
30JSON: TypeAlias = dict[str, any]
31
32# Runtime behavior
33print(type(UserID))  # <class 'typing.TypeAliasType'>
34print(UserID.__value__)  # <class 'int'>