Python overriding setter to an attribute with no setter?

Question

I have a class A made by someone else, that I cannot edit:

class A:
    def __init__(self, x):
        self.x = x

Now I'm trying to inherit my own class B from A, and have x as a property instead of an attribute. Is this possible?

I already tried:

class B(A):
    def __init__(self, x):
        super().__init__(x)

    @property
    def x(self):
        return super().x

    @x.setter
    def x(self, x):
        super().x = x
        print(x)  # my stuff goes here

But as I expected, it's not possible: AttributeError: 'super' object has no attribute 'x'

Is there any other method, some workaroud maybe?

Answer 1

No, you cannot use super() for anything other than class attributes; x is an instance attribute, and there is no inheritance mechanism for attributes.

Instance attributes live in a single namespace; there is no 'parent instance' attribute namespace.

You can still reach the attribute in the instance __dict__ object:

class B(A):
    @property
    def x(self):
        return self.__dict__['x']

    @x.setter
    def x(self, x):
        self.__dict__['x'] = x
        print(x)  # my stuff goes here

A property is a data descriptor, meaning that it is looked up before the instance attributes are consulted (see the descriptor howto), but you can still access it directly.