6.3. Calculate Expenses

A group of people who needs to do some shopping wants to know how much they will spend in total approximately. As being a good samaritan, you decide to help them. You have the following function to calculate the total price of a shopping list, at hand. This function takes a shopping list as a list of tuples where the first element is supposed to be the name of an item as string, where the second one should be the price of this item as float.

def sum_prices(shopping_list):

    total = 0
    for (item, price) in shopping_list:
        total += price

    return round(total, 2)

This simple function can help you to calculate the total cost of each of the given shopping lists by rounding it 2 digits after the decimal point. However, although people know all of the items that they want to buy, they might not be sure about the price of each one. So, a list provided by one of these people may include a note indicating their lack of knowledge near the item’s name, instead of the price. Since these notes can differ from person to person, you have to deal with this problem in a way that covers all such notes.

Write a function named calculate_expenses which takes the list of shopping lists, where each of them is a list of tuples as explained above. This function must return a list including the total prices for the complete shopping lists as floats and "Incomplete" string for the incomplete ones using the function above.

Sample I/O:

>>> calculate_expenses([[("chocolate", 4.25), ("jambonbutter", 4.75), ("ice cream", 3.5), ("milk", 3.25)], [("coffee", 4.75), ("olive", 2.25), ("ice cream", 2.99)]])
[15.75, 9.99]

>>> calculate_expenses([[("coffee", 2.5), ("milk", "dunno"), ("ice cream", 2.75)],
                        [("candy", 2.99), ("chocolate", 3.99), ("tea", 3.5), ("coffee", 2.99), ("olive", 2.99)],
                        [("tea", 3.99), ("coffee", 2.5), ("olive", 2.25), ("chocolate", 4.25), ("jambonbutter", 4.25), ("egg", 2.25)]])
['Incomplete', 16.46, 19.49]

>>> calculate_expenses([[("tea", 4.99), ("olive", 3.5), ("chocolate", 4.75), ("coffee", 3.99),
                         ("milk", 2.99), ("egg", 3.99), ("jambonbutter", "not sure")],
                         [("jambonbutter", 3.5), ("egg", 3.75), ("tea", 3.99), ("coffee", 4.5), ("olive", 3.75)],
                         [("jambonbutter", 3.99), ("milk", 3.5), ("chocolate", 4.25), ("ice cream", 3.5),
                          ("cheese", 2.75), ("candy", 2.75), ("tea", 4.5), ("olive", "unknown")],
                          [("ice cream", 3.99), ("olive", 3.75), ("chocolate", 2.99), ("coffee", 4.5),
                          ("milk", 3.25), ("tea", 2.25), ("candy", 4.25), ("cheese", 4.75)],
                          [("ice cream", 3.75), ("coffee", 3.25), ("candy", "unknown"),
                          ("chocolate", 3.99), ("egg", 4.99), ("olive", 3.25), ("milk", 2.5)]])
['Incomplete', 19.49, 'Incomplete', 29.73, 'Incomplete']

Show the Answer

def calculate_expenses(shopping_lists):
    result = []
    for lst in shopping_lists:
        try:
            result.append(sum_prices(lst))
        except TypeError:
            result.append("Incomplete")
    return result