Example of how classes work in python

ClassExample.py

# import the math module (this will be used in Circle class)
import math

# created a generic shape class
class Shape:
    # the function to initialize the shape
    def __init__(self, width, height):
        # the properties of the shape
        self.width = width
        self.height = height

    # the function to get area, but not implelmented
    def get_area(self):
        pass

    # overridden 'tostring' method that will return all properties
    # see lines 49, 53, 57
    def __str__(self):
        return str(vars(self))

# rectangle is a subclass of shape
class Rectangle(Shape):
    # overloaded get_ara method: w * h
    def get_area(self):
        return self.width * self.height;

# Square is a subclass of Rectangle
class Square(Rectangle):
    # added a new __init__ method
    def __init__(self, side_length):
        # sets width and height to side_length
          self.width = self.height = side_length

# circle is a subclass of Shape
class Circle(Shape):
    # custom init w/ radius
    def __init__(self, radius):
        # make new radius paramter
        self.radius = radius
        # set the width and height (optional, but good to stay consistent)
        self.width = self.height = radius * 2

    # area of circle: 2πr
    def get_area(self):
        return math.pi * 2 * self.radius


shape = Shape(4, 5)
print(str(shape))                # prints {'width': 4, 'height': 5}
print(shape.get_area())     # prints None

sq = Square(4)
print(str(sq))                   # prints {'width': 4, 'height': 4}
print(sq.get_area())        # prints 16

c = Circle(4)
print(str(c))                    # prints {'width': 8, 'radius': 4, 'height': 8}
print(c.get_area())         # prints 25.1327412287