What does return do? Nothing is ever returned

Question

I have been learning Python for some days now. However, I do not understand return. I have read several explanations from my textbooks and online; they don\'t help!

Answer 1

return returns a value from a function:

def addseven(n):
    return n + 7

a = 9
b = addseven(a)
print(b)        # should be 16

It can also be used to exit a function:

def addseventosix(n):
    if n != 6:
        return
    else:
        return n + 7

However, even if you don't have a return statement in a function (or you use it without specifying a value to return), the function still returns something - None.

def functionthatisuseless(n):
    n + 7

print(functionthatisuseless(8))        # should output None

Sometimes you might want to return multiple values from a function. However, you can't have multiple return statements - control flow leaves the function after the first one, so anything after it won't be executed. In Python, we usually use a tuple, and tuple unpacking:

def addsevenandaddeight(n):
    return (n+7, n+8)        # the parentheses aren't necessary, they are just for clarity

seven, eight = addsevenandaddeight(0)
print(seven)        # should be 7
print(eight)        # should be 8

return statements are what allow you to call functions on results of other functions:

def addseven(n):
    return n+7

def timeseight(n):
    return n*8

print(addseven(timeseight(9))

# what the intepreter is doing (kind of):
# print(addseven(72))    # 72 is what is returned when timeseight is called on 9
# print(79)
# 79