Python inheritance changing child class field

I am creating a database in a for of classes with inheritance. I would like Child class to inherit all field of parent class, however it doesn't happen as I am getting "AttributeError: 'Child' object has no attribute 'default'". If I define 'default' variable in Child class, I will get it working, but I want that Child inherited parent value for 'default' and not redefine it again at Child class. If I don't specify __init__ method in Child class, all fields are inherited, but I can't change their value.

#!/usr/bin/env python3
import sys

class Parent():
    def __init__(self, y, x):
        self.result = self.action(x,y)
        default = 5
    def action(self,x,y):
        return (x*y)
    def setResult(self, x):
        def __init__(self, y, x):
            self.result = x
class Child(Parent):

    def __init__(self, y, x):
        self.result = self.action(x,y)
    def action(self,x,y):
        return (x/y)


def main(argv):
    data = Child(2,3)
    print (data.result)
    print (data.default)

if __name__ == "__main__":
    main(sys.argv[1:])

To consolidate the comments you received into an actual answer:

class Parent():
    def __init__(self, y, x):
        self.result = self.action(x,y)
        self.default = 5 #----- this requires a "self" to attach to any instance of the class

class Child(Parent):
    def __init__(self, y, x):
        super().__init__(y, x)
        self.result = self.action(x,y)

To restate everything that has been stated in the comments:

You are overriding __init__ by making a function for it.

__init__ is a built-in function, if you don't make one yourself - python uses one it makes itself. __init__ is always run when a class is being initiated.

When you declare variables to self in this function, you are adding the variables to any instance of the class that is created. (as opposed to using self in some other function)

By writing your own version of __init__ you are taking on the burden of making sure that it creates every value the class is supposed to have - for cases where you want to make use of inheritance, this is why we have the super() function.

The super() function is used to give access to methods and properties of a parent or sibling class.

By calling super().__init__(y, x) you call Parent()'s __init__ function and thus 'inherit' its values / settings / properties.

Just to crystallize the subject more - the following two classes are (effectively) identical:

class Child(Parent):
    def __init__(self, y, x):
        super().__init__(y, x)
    def action(self,x,y):
        return (x/y)

class Child(Parent):
    def action(self,x,y):
        return (x/y)

Further reference:<br>
https://www.w3schools.com/python/gloss_python_class_init.asp <br>
https://www.w3schools.com/python/ref_func_super.asp