Again... Experimenting with `return` but-in Python

Examples

As usual, let's dive into a bit of experimentation to better understand return, but this time with Python. (I felt uncomfortable with Perl as I mentioned in the previous post.) Anyway, back to Python! In Python, the return keyword is used to stop a function’s execution and give back a value from that function. But there are a few things worth understanding about how it works. For example, here’s a function where we want to add two numbers and print the result:

def main(a, b):
    c = a + b
    return c
    print(c)  # This line won't execute

main(19, 18)

In this function, main takes in two parameters, a and b, adds them together, then returns the result with return c. After the return, there’s a print(c), which should print out c. But when we run this, it doesn’t print anything. Why?

Why `print` Doesn’t Work After `return`

When Python hits return, it immediately stops the function’s execution. So anything that comes after return (in this case, print(c)) never runs. If we want c to print, we need to move print(c) before return. Here’s how it looks fixed:

def main(a, b):
    c = a + b
    print(c)  # Print the value before returning it
    return c

main(19, 18)

With this order, print(c) gets executed, so the value of c (37) prints before the function returns it.

Alternative: Printing the Function’s Return Value

There’s another way to print the result without changing the position of return. Instead of using print inside the function, we can print the return value of main directly:

def main(a, b):
    c = a + b
    return c

print(main(19, 18))  # Print the result of the function call

With this approach, main just returns the value of c, while the print outside of it takes care of printing it.

Using `print` and `return` Together in One Line

Alternatively, we can write print along with return in a single line, like this:

def main(a, b):
    c = a + b
    return print(c)  # Note: This returns None

main(19, 18)

In this example, print(c) will print when the function runs. But there’s a catch: in Python, print always returns None. So, even though this code works for printing the result, the value returned by main isn’t c—it’s None.

Best Practice Recommendation

If you want the function to both print and return the value of c, use code like this:

def main(a, b):
    c = a + b
    print(c)
    return c

main(19, 18)

Or, even simpler, you can skip return entirely since Python automatically returns the last evaluated expression:

def main(a, b):
    c = a + b
    print(c)

main(19, 18)

Again... Experimenting with return but-in Python