shapes.py

class Shape:
    def area(self):
        raise NotImplementedError

    def perimeter(self):
        raise NotImplementedError


class Rectangle(Shape):
    def __init__(self, side1, side2):
        self.side1 = side1
        self.side2 = side2

    def area(self):
        return self.side1 * self.side2

    def perimeter(self):
        return (self.side1 * 2) + (self.side2 * 2)


class Triangle(Shape):
    def __init__(self, side1, side2, side3):
        pass


class Circle(Shape):
    def __init__(self, radius):
        pass


rectangle = Rectangle(10.0, 50.0)
triangle = Triangle(3.0, 7.0, 11.0)
circle = Circle(14)

print('Rectangle area: {}, perimeter: {}'.format(
    rectangle.area(), rectangle.perimeter()))

print('Triangle area: {}, perimeter: {}'.format(
    triangle.area(), triangle.perimeter()))

print('Circle area: {}, perimeter: {}'.format(
    circle.area(), circle.perimeter()))