我正在尝试实现一个通用协议。我的目的是使用一个带有简单getter的widget[key\u type,value\u type]协议。mypy抱怨 Protocol[K, T]
这样就变成了 Protocol[K_co, T_co]
. 我已经去掉了所有其他的限制,但我甚至不能得到最基本的情况, widg0: Widget[Any, Any] = ActualWidget()
,工作。actualwidget.get应与完全兼容 get(self, key: K) -> Any
,这让我觉得我在某种程度上使用泛型/协议是错误的,或者mypy无法处理这个问题。
来自mypy的命令/错误:
$ mypy cat_example.py
cat_example.py:34: error: Argument 1 to "takes_widget" has incompatible type "ActualWidget"; expected "Widget[Any, Any]"
cat_example.py:34: note: Following member(s) of "ActualWidget" have conflicts:
cat_example.py:34: note: Expected:
cat_example.py:34: note: def [K] get(self, key: K) -> Any
cat_example.py:34: note: Got:
cat_example.py:34: note: def get(self, key: str) -> Cat
Found 1 error in 1 file (checked 1 source file)
或者,如果我试图用 widg0: Widget[Any, Any] = ActualWidget()
:
error: Incompatible types in assignment (expression has type "ActualWidget", variable has type "Widget[Any, Any]")
完整代码:
from typing import Any, TypeVar
from typing_extensions import Protocol, runtime_checkable
K = TypeVar("K") # ID/Key Type
T = TypeVar("T") # General type
K_co = TypeVar("K_co", covariant=True) # ID/Key Type or subclass
T_co = TypeVar("T_co", covariant=True) # General type or subclass
K_contra = TypeVar("K_contra", contravariant=True) # ID/Key Type or supertype
T_contra = TypeVar("T_contra", contravariant=True) # General type or supertype
class Animal(object): ...
class Cat(Animal): ...
@runtime_checkable
class Widget(Protocol[K_co, T_co]):
def get(self, key: K) -> T_co: ...
class ActualWidget(object):
def get(self, key: str) -> Cat:
return Cat()
def takes_widget(widg: Widget):
return widg
if __name__ == '__main__':
widg0 = ActualWidget()
#widg0: Widget[str, Cat] = ActualWidget()
#widg0: Widget[Any, Any] = ActualWidget()
print(isinstance(widg0, Widget))
print(isinstance({}, Widget))
takes_widget(widg0)
暂无答案!
目前还没有任何答案,快来回答吧!