examples/classes/inheritance/shapes.py
from __future__ import print_function

class Point(object):
    def __init__(self, x, y):
        print('__init__ of Point')
        self.x = x
        self.y = y

    def move(self, dx, dy):
        self.x += dx
        self.y += dy

class Circle(Point):
    def __init__(self, x, y, r):
        print('__init__ of Circle')
        Point.__init__(self, x, y)
        # super(Circle, self).__init__(x, y)
        self.r = r

    def area(self):
        return self.r * self.r * 3.14
examples/classes/inheritance/circle.py
from __future__ import print_function
import shapes

c = shapes.Circle(2, 3, 10)   # __init__ of Circle
                              # __init__ of Point
print(c)          # <shapes.Circle instance at 0x7fb58c31ccb0>
print(c.x)        # 2
print(c.y)        # 3
print(c.r)        # 10

c.move(4, 5)
print(c.x)        # 6
print(c.y)        # 8
print(c.area())   # 314.0