How to not have to type self in init when subclassing

Question

MCVE:

class A:
    def __init__(self, num: int):
        self.value = num

class B(A):
    def __init__(self): # Mypy: function is missing a type annotation
        A.__init__(self, 7) # Mypy: Expression has type "Any"

I would like Mypy to not force me to have to type self. It seems obvious to me what the type of self is, and Mypy is able to figure it out for A, so why not B?

How can I define B such that I'm not forced to do the following?

class A:
    def __init__(self, num: int):
        self.value = num

class B(A):
    def __init__(self: 'B'):
        A.__init__(self, 7)

Answer 1

You need to annotate the return type of your signature:

class Foo:
    def __init__(self) -> None:
        pass

Mypy will let you omit the return type on specifically the constructor if one or more other arguments are annotated, but you'll need to include it on no-argument constructors.