Practical Programming, 2nd Edition

Dealing with Situations That Your Code Doesn’t Handle

You’ll often write a function that only works in some situations. For example, you might write a function that takes as a parameter a number of people who want to eat a pie and returns the percentage of the pie that each person gets to eat. If there are five people, each person gets 20% of the pie; if there are two people, each person gets 50%; if there is one person, that person gets 100%; but if there are zero people, what should the answer be?

Here is an implementation of this function:

def pie_percent(n):
    """ (int) -> int

    Assuming there are n people who want to eat a pie, return the percentage
    of the pie that each person gets to eat.

    >>> pie_percent(5)
 20 ...