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5.3. Return Value

Functions could return a value as a result of its calling. This page covers various features and details about the return statement.

We've already seen in previous sections how return works. It returns a value back to the caller.

def add(n1, n2):
    return n1 + n2

result = add(5, 2)
print(result)

7

Here, result is assigned the value returned by function.

Behaviour of return

The return statement is like a terminating statement for a function. When you return something, the function terminates with the returned value.

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def check_password(password):
    if password == '1234':
        return True

    return False

print(check_password('1234'))
print(check_password('123456'))

True
False

In this case, when we passed 1234 to password parameter, the if condition was satisfied and return True on line 3 was executed. As soon as this happened, the rest of the function body was skipped and True was yielded back to caller.

On the otherhand, when if condition wasn't satisfied (second function call), the rest of function body was executed and False was returned.

This is equivalent to the following code but the else block is unnecessary here:

# equivalent to code shown above
def check_password(password):
    if password == '1234':
        return True
    else:
        # This else block is redundant and unnecessary!
        return False

print(check_password('1234'))
print(check_password('123456'))

True
False

Return nothing

In some cases, a function performs an action and returns nothing. "Nothing" in Python is represented using the None value.

def greet(name):
    print(f'Hello, {name}!')

result = greet('John')
print(result)

Hello, John!
None

Since greet() has no return statement and isn't returning anything, it simply returns a None value representing nothing was returned.

Return vs Print

Do not confuse "returning a value" and "printing a value". In cases shown previously, both might seem to do the same thing but there's a difference.

print() itself is a builtin function that simply outputs the given message to console.

return on the other hand, is a keyword used in a function to yield the value back to caller.

When we do, print(2), we're telling Python to show the output on screen. In case of return 2 inside a function, we're telling Python to assign the value 2 to the call of the given function.

def print_value():
    print(12)

def return_value():
    return 12

print_value()  # prints 12
return_value()  # does nothing

12

However, to print result of return_value, we use the print again:

print_value()  # prints 12
print(return_value())  # prints returned value of return_value()

12
12

Returning multiple values

A function could return a sequence of values. To do so, separate the values to return using a comma ,.

For example, consider this function that returns result of division and remainder:

def divide_and_remainder(n1, n2):
    return n1 / n2, n1 % n2

values = divide_and_remainder(5, 2)
print(values[0])
print(values[1])

2.5
1

In fact, the values returned are stored as a tupleand could be unpacked too:

quotient, remainder = divide_and_remainder(5, 2)
print(quotient)
print(remainder)

2.5
1

Note

Function shown in above example is same as builtin divmod() function.

Returning Nested Functions

Nested functions are also referred to as closures and are used to retain values from original (outer) function even after the original function is done executing.

def factor(a):
    def inner(b):
        return a * b

    return inner

doubler = factor(2)
tripler = factor(3)

print(doubler(20))
print(tripler(20))

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In this case, we're creating a function inside factor everytime it is called and returning it.