Return values and defaults

print shows a value. return gives a value back to whoever called the function, so you can use it.

def add(a, b):
    return a + b

total = add(2, 3)
print(total * 10)    # 50

When Python reaches return, the function ends right there.

Default values

A parameter can have a default, used when you don't pass that argument:

def area(length, width=1):
    return length * width

print(area(5, 3))   # 15
print(area(5))      # 5   (width is 1)

In tests, functions are checked by what they return. If you print instead of return, the caller gets None.