"Animal"的"foo"的重载变体与参数类型"str"匹配

Question

我有一个文件t.py，它有一个类Animal和一个子类Cat。两者都有方法foo，该方法根据布尔值inplace的值有不同的返回类型。

文件的完整代码:

# t.py
from __future__ import annotations
from typing import TypeVar, Optional, overload, Literal 
CatOrDog = TypeVar("CatOrDog", bound="Animal")

class Animal:
@overload
def foo(self: CatOrDog, inplace: Literal[False], bar) -> CatOrDog:
...
@overload
def foo(self: CatOrDog, inplace: Literal[True], bar) -> None:
...
def foo(
self: CatOrDog, inplace: bool = False, bar=None
) -> Optional[CatOrDog]:
...
def ffill(self) -> Optional[CatOrDog]:
return self.foo(bar="a")

class Cat(Animal):
@overload
def foo(self, inplace: Literal[False], bar) -> Cat:
...
@overload
def foo(self, inplace: Literal[True], bar) -> None:
...
def foo(self, inplace: bool = False, bar=None) -> Optional[Cat]:
...

如果我在上面运行mypy，我得到

$ mypy t.py 
t.py:23: error: No overload variant of "foo" of "Animal" matches argument type "str"
t.py:23: note: Possible overload variants:
t.py:23: note:     def foo(self, inplace: Literal[False], bar: Any) -> Animal
t.py:23: note:     def foo(self, inplace: Literal[True], bar: Any) -> None
Found 1 error in 1 file (checked 1 source file)

我如何才能正确地重载foo，以便我可以调用self.foo(bar="a")?我试过设置bar: Any，但这不起作用。

Answer 1

您需要允许其中一个重载的默认参数，并在ffill方法中为self设置正确的类型。

:

from __future__ import annotations
from typing import TypeVar, Optional, overload, Literal 
CatOrDog = TypeVar("CatOrDog", bound="Animal")

class Animal:
@overload
def foo(self: CatOrDog, inplace: Literal[False]=..., bar=...) -> CatOrDog:
...
@overload
def foo(self: CatOrDog, inplace: Literal[True], bar=...) -> None:
...
def foo(
self: CatOrDog, inplace: bool = False, bar=None
) -> Optional[CatOrDog]:
...
def ffill(self: CatOrDog) -> Optional[CatOrDog]:

return self.foo(bar="a")

class Cat(Animal):
@overload
def foo(self, inplace: Literal[False]=..., bar=...) -> Cat:
...
@overload
def foo(self, inplace: Literal[True], bar=...) -> None:
...
def foo(self, inplace: bool = False, bar=None) -> Optional[Cat]:
...

见https://mypy-play.net/?mypy=latest& python = 3.9, = 49要点da369f6343543769eed2060fa61639