classes_with_lists_as_attribues.py

cost_of_items = {'apple': 4,
                 'cake': 6,
                 'doughnut': 12}

class ShoppingBasket:
    """
    A class for a shopping basket with attributes for the cost and the contents of a shopping basket
    """
    def __init__(self):
        self.cost = 0  # Initialising a cost of 0 (basically the value of the basket when someone picks it up
        self.contents = []  # Initialising the contents of the basket as an empty list
    def add_item(self, item):
        """
        A method to add an item to the basket, this appends it to the list but also updates the cost
        """
        self.contents.append(item)
        self.cost += cost_of_items[item]

basket = ShoppingBasket()
print basket.cost
print basket.contents
print 20 * '='  # We're putting cake in the basket
basket.add_item('cake')
print basket.cost
print basket.contents
print 20 * '='  # We're putting cake in the basket again (cake is nice)
basket.add_item('cake')
print basket.cost
print basket.contents
print 20 * '='  # We're putting an apple in the basket
basket.add_item('apple')
print basket.cost
print basket.contents
print 20 * '='  # We're putting a doughnut in the basket
basket.add_item('doughnut')
print basket.cost
print basket.contents