How to Think Like a Computer Scientist - Iteration Problem

[rubicana]

Code from here

def checkout():
    total = 0
    count = 0
    moreItems = True
    while moreItems:
        price = float(input('Enter price of item (0 when done): '))
        if price != 0:
            count = count + 1
            total = total + price
            print('Subtotal: $', total)
        else:
            moreItems = False
    average = total / count
    print('Total items:', count)
    print('Total $', total)
    print('Average price per item: $', average)

checkout()

On the site underneath the code it states

"If you enter zero the first time you are asked for a price, the loop will end, and the program will try to divide by zero. Use an if/else statement outside the loop to avoid the division by zero and tell the user that you can’t compute an average without data."

Haven't been able to work this out - a seemingly simple if/else statement outside of the loop to catch the divide by zero. Any help gratefully received. Many thanks Tom