"""Exercise 6.3.1 — Relying on a shared method

Chapter 6: Objects — Everyday Programming

Different shapes each provide an area() method, so one function can
total them all.

This program contains exactly one bug. Solution: sol_6_3_1.py
"""

class Square:
    def __init__(self, side):
        self.side = side

    def area(self):
        return self.side * self.side

class Triangle:
    def __init__(self, base, height):
        self.base = base
        self.height = height

    def area(self):
        return self.base * self.height / 2

def total_area(shapes):
    total = 0
    for shape in shapes:
        total = total + shape.area
    return total

print(total_area([Square(4), Triangle(6, 3)]))   # 25.0