mypy:“__getitem__"的签名；与超类型“序列"不兼容

问题描述

我有一个继承自 MutableSequence 的类，如下所示:

I have a class that inherits from MutableSequence like this:

class QqTag(MutableSequence):
    def __init__(self):
        self._children = []
    def __getitem__(self, idx: int) -> 'QqTag':
        return self._children[idx]

mypy 抱怨 __getitem__"的签名与超类型Sequence"不兼容.

在Sequence中，该方法定义为:

@abstractmethod
def __getitem__(self, index):
    raise IndexError

那么，问题是什么?为什么 mypy 对我的实现不满意?

So, what's the problem and why mypy isn't happy with my implementation?

推荐答案

正如评论中提到的，也可以传递一个 typeof 切片.即，将 idx: int 更改为 idx: Union[int, slice].

As mentioned in comments, a typeof slice can also be passed. Ie, change idx: int to idx: Union[int, slice].

这会让 mypy 开心(至少在我的机器上；):

This will make mypy happy (at least on my machine ;):

class QqTag(MutableSequence):
    def __init__(self):
        self._children = []

    def __getitem__(self, idx: Union[int, slice]) -> 'QqTag':
        return self._children[idx]

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