英文:
Expected no type arguments for class "Self"
问题
我有一个通用类，其中有一个next方法，该方法返回一个参数化为不同类型变量的自身实例。
我可以使用"来指定next方法的返回类型，以引用类本身：
DataIn = TypeVar('DataIn')
DataOut = TypeVar('DataOut')
@dataclass
class Msg(Generic[DataIn]):
source: str
data: DataIn
def next(self, data: DataOut) -> "Msg[DataOut]":
"""
创建一个具有相同源但不同数据的新消息
"""
return Msg(source=self.source, data=data)
我想使用PEP 673中的Self类型来避免使用"：
def next(self, data: DataOut) -> Self[DataOut]:
但是在Pylance / Pyright中无法通过类型检查：
Expected no type arguments for class "Self"
文档中说：“Self也可以在通用类方法中使用”，但没有显示这个特定的用例。
它是否被支持？
英文:
I have a generic class, with a next method which returns an instance of itself parameterized to a difference type variable.
I can specify the next method's return type using " to reference the class itself:
DataIn = TypeVar('DataIn')
DataOut = TypeVar('DataOut')
@dataclass
class Msg(Generic[DataIn]):
source: str
data: DataIn
def next(self, data: DataOut) -> "Msg[DataOut]":
"""
Create a new message with the same source but different data
"""
return Msg(source=self.source, data=data)
I would like to use the PEP 673 Self type to avoid the "':
def next(self, data: DataOut) -> Self[DataOut]:
But that fails to type check in Pylance / Pyright:
Expected no type arguments for class "Self"
The docs say: "Self can also be used in generic class methods", but don't show this specific use case.
Is it supported?
答案1
得分: 0
这是不支持的，而且是有意不支持的。在通用类型的情况下，Self（在普通方法中，而不是类方法中）指的是已经参数化的实例。
引用你提供的文档（即相同的部分）：
注意，我们拒绝使用带有类型参数的
Self，比如Self[int]。这是因为它会对self参数的类型产生歧义，并引入不必要的复杂性：
class Container(Generic[T]):
def foo(
self, other: Self[int], other2: Self,
) -> Self[str]: # 被拒绝
...
在这种情况下，我们建议为self使用显式类型：
class Container(Generic[T]):
def foo(
self: Container[T],
other: Container[int],
other2: Container[T]
) -> Container[str]: ...
英文:
This is not supported, and not supported intentionally. In case of generic types Self refers (in regular methods - not classmethods) to some already parametrized instance.
Quoting the docs (even the same section) that you linked:
> Note that we reject using Self with type arguments, such as Self[int]. This is because it creates ambiguity about the type of the self parameter and introduces unnecessary complexity:
class Container(Generic[T]):
def foo(
self, other: Self[int], other2: Self,
) -> Self[str]: # Rejected
...
> In such cases, we recommend using an explicit type for self:
class Container(Generic[T]):
def foo(
self: Container[T],
other: Container[int],
other2: Container[T]
) -> Container[str]: ...
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