Exercise · Classes · lesson 11 of 11

Exercise: shape areas

The stub already has the class Shape, a shape with no __init__ of its own whose method area(self) returns 0; do not change it. The math module is already imported in the stub too. Write:

a class Rect(width, height), a rectangle and a child class of Shape, whose method area(self) returns width * height;
a class Circle(radius), a circle and also a child class of Shape, whose method area(self) returns math.pi * radius ** 2, where math.pi is the number π;
a function total_area(shapes) that returns the sum of the areas of all the shapes in the list shapes.

Examples:

Rect(2, 3).area() → 6
Circle(1).area() → 3.141592653589793
total_area([Rect(2, 3), Circle(1)]) → 9.141592653589793

Constraints: sizes are positive numbers; the list may hold instances of Shape, Rect and Circle; for an empty list, total_area returns 0.

Do not add extra imports unless the task says so explicitly.

shapes.py — python

python · 27 lines

import math


class Shape:
    def area(self):
        return 0


class Rect(Shape):
    def __init__(self, width, height):
        pass

    def area(self):
        return None


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

    def area(self):
        return None


def total_area(shapes):
    return None

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