Returned Function Values

So far, our functions have done something (printed output) but not produced a value for the calling code to use. Functions that return values are far more flexible.

The return Statement

Use return to send a value back to the caller:

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>>> def add(a, b):
...     return a + b
...
>>> add(3, 4)
7

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The returned value can be used in any expression:

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>>> def add(a, b):
...     return a + b
...
>>> add(3, 4) * 2
14
>>> print(f"Sum: {add(10, 5)}")
Sum: 15

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Example: Weekly Wages

Here is a function that calculates wages including overtime:

def weekly_wages(hours, rate):
    """Return total weekly wages including overtime pay above 40 hours."""
    if hours <= 40:
        return hours * rate
    else:
        overtime = hours - 40
        return 40 * rate + overtime * rate * 1.5


hours = float(input("Enter hours worked: "))
rate = float(input("Enter hourly rate: $"))
pay = weekly_wages(hours, rate)
print(f"Weekly wages: ${pay:.2f}")

Sample run:

Enter hours worked: 45
Enter hourly rate: $20
Weekly wages: $950.00

The function computes the value and returns it; the calling code decides what to do with it (here, print it).

Functions Without return

A function that does not have a return statement (or that reaches the end without hitting one) automatically returns None:

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>>> def say_hi():
...     print("Hi!")
...
>>> result = say_hi()
Hi!
>>> print(result)
None

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A function that performs an action but returns no value implicitly returns None. Use return only when the caller needs a value.

Early Return

A function can have more than one return statement. Python exits the function and returns as soon as it hits any return:

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>>> def absolute_value(x):
...     if x >= 0:
...         return x
...     return -x
...
>>> absolute_value(-5)
5
>>> absolute_value(5)
5

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The second return is only reached if x < 0.