小编mac*_*jan的帖子

以下代码无法按预期工作。显然，我不能在类定义中使用类自己的类型：

class Foo:
    def __init__(self, key :str) -> None:
        self.key = key

    def __eq__(self, other :Foo) -> bool:
        return self.key == other.key

print('should be true: ', Foo('abc') == Foo('abc'))
print('should be false: ', Foo('abc') == Foo('def'))

运行结果如下：

Traceback (most recent call last):
  File "class_own_type.py", line 1, in <module>
    class Foo:
  File "class_own_type.py", line 5, in Foo
    def __eq__(self, other :Foo) -> bool:
NameError: name 'Foo' is not defined

此外，检查代码mypy返回：

class_own_type.py:5: error: Argument 1 of "__eq__" incompatible with supertype …