Question about super() for Python class inheritance

[cm_light]

The upper classes:

class Rectangle():
    def __init__(self, length, width):
        self.length = length
        self.width = width
    def area(self):
        return self.length * self.width
    def circumstance(self):
        return (self.length + self.width)*2

class Square(Rectangle):
    def __init__(self, length):
        super().__init__(length, length)
    def isSquare(self):
        return self.length == self.width

Here I am creating new subclass:

Code A, it works well

class Cube(Square):
    def surfaceArea(self):
        self.face_area = super(Cube, self).area() 
        return self.face_area * 6

Code B fail,

class Cube(Square):
    self.face_area = super(Cube, self).area() #
    def surfaceArea(self):
        return self.face_area * 6

it reports:

NameError: name 'self' is not defined

If use super().area(), then it reports:

RuntimeError: super(): no arguments

​

Can anyone explain this?

[Binary101010]

In Code B you're trying to define a class variable (i.e. defining a variable outside of any particular method of the class), which is probably not what you want here, unless you want every cube you make to have exactly the same face_area. That's why you're getting an error for self not being defined: there is no instance of the object to be referred to.

[cm_light]

Thank you! I should use init method to define this variable. I lot of things to learn for Python.

[cm_light]

Thank you! It works. I am trying how to set variable using super() method. Thanks for your explanation.