Defining and Using Functions

We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.

—Will Durant, The Story of Philosophy

We have already seen many examples of simple functions. Functions let you write and package code so that it may be used more than once. Suppose you want to print out the odd integers greater than 0 and less than 6. This works:

for i in range(6):
    if i % 2 == 1:
        print(f"{i} ", end="")

1 3 5

Instead of 6, what if you wanted to use 9 or 16 or 1,036? You do not want to repeat the above every time you change the upper bound. Instead, you code a function that is called repeatedly with different values.

def odd_numbers_less_than(n):
    # this function prints out all odd numbers greater
    # than 0 and less than n
    for i in range(n):
        if i % 2 == 1:
            print(f"{i} ", end="")

odd_numbers_less_than...