提问人：Boris Mirzakhanyan 提问时间：9/28/2023 最后编辑：Boris Mirzakhanyan 更新时间：9/28/2023 访问量：80
如何在Python中正确使用类型提示？
How to properly use type hints in Python?
问：
我不知道如何在我的type_casting函数中正确使用类型提示。
def type_casting(var, _type):
if _type not in (str, int, float, bool):
return Exception
return _type(var)
assert type_casting("55", int) == 55
assert type_casting(55, str) == "55"
如何在Python中正确使用类型提示？
我想做这样的事情：
T = int | float | str | bool
def type_casting(var: Any, _type: Type[T]) -> T:
答：
1赞
Noé Duruz
9/28/2023
#1
这似乎有点麻烦，但您可以让它处理一些重载。请注意，您必须从较窄的类型开始，否则永远无法访问它，并且 MyPy 会抱怨它。
from typing import TYPE_CHECKING, Any, overload
T = int | float | str | bool
@overload
def type_casting(var: Any, type_: type[bool]) -> bool:
...
@overload
def type_casting(var: Any, type_: type[int]) -> int:
...
@overload
def type_casting(var: Any, type_: type[float]) -> float:
...
@overload
def type_casting(var: Any, type_: type[str]) -> str:
...
def type_casting(var: Any, type_: type[T]) -> T:
if type_ not in (str, int, float, bool):
raise Exception
return type_(var)
my_int = type_casting(55, int)
my_float = type_casting(55, float)
my_str = type_casting(55, str)
my_bool = type_casting(55, bool)
if TYPE_CHECKING:
reveal_type(my_int) # note: Revealed type is "builtins.int"
reveal_type(my_float) # note: Revealed type is "builtins.float"
reveal_type(my_str) # note: Revealed type is "builtins.str"
reveal_type(my_bool) # note: Revealed type is "builtins.bool"
assert type_casting("55", int) == 55
assert type_casting(55, str) == "55"
2赞
Yuri R
9/28/2023
#2
您可以使用 和AnyTypeVar
from typing import TypeVar, Type, Any
T = TypeVar('T', int, float, str, bool)
def type_casting(var: Any, _type: Type[T]) -> T:
if _type not in (str, int, float, bool):
raise ValueError(f"Unsupported type {_type}")
return _type(var)
你可以在这里参考 TypeVar
评论
0赞
Noé Duruz
9/28/2023
这比我的解决方案优雅得多！
下一个：带参数的函数的返回类型
评论
|Type[...]Type[int] | Type[float], ...