Returned Function Values

Note

Source: Adapted from the C# edition (functions/funcreturn.rst). The weekly-wages example mirrors the C# original. Python-specific details (implicit None return, early return pattern) are original additions.

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:

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

result = add(3, 4)
print(result)

Output:

7

The returned value can be used in any expression:

>>> add(3, 4) * 2
14
>>> print(f"Sum: {add(10, 5)}")
Sum: 15

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:

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

This is Python’s way of handling what C# calls void functions. 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:

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

The second return is only reached if x < 0.