Well, I fact, I was playing with metaclasses and descriptors, and I was thinking about a way to use the famous variable annotation to instatiate decrptors like this:

class Point(metaclass=MyMeta):

    x: int

    y: int

class Circle(metaclass=MyMeta):

    center: Point

    radius: PositiveInteger

Here the radius must be [strictly] positive, but since I'm using the annotations to get the type to test in the __set__ method of the descriptor, I didn't found a more elegant way than that...

And it was before I knew the existance of dataclasses!!! I was pretty shocked by the way. Maybe I can make this compatible with it anyway.