Type Hints

Syntax

• typing.Callable[[int, str], None] -> def func(a: int, b: str) -> None
• typing.Mapping[str, int] -> {“a”: 1, “b”: 2, “c”: 3}
• typing.List[int] -> [1, 2, 3]
• typing.Set[int] -> {1, 2, 3}
• typing.Optional[int] -> None or int
• typing.Sequence[int] -> [1, 2, 3] or (1, 2, 3)
• typing.Any -> Any type
• typing.Union[int, str] -> 1 or “1”
• T = typing.TypeVar(‘T’) -> Generic type

Remarks

Type Hinting, as specified in PEP 484, is a formalized solution to statically indicate the type of a value for Python Code. By appearing alongside the typing module, type-hints offer Python users the capability to annotate their code thereby assisting type checkers while, indirectly, documenting their code with more information.