Python Return Use Cases

Question

Why should I use return in python functions when I can use print() and it gives me the same result? Is there any specific use cases or there's something that I can't understand? I'll be glad if you describe the answer simple and clear:)

Using print:

def test(var):
    print(var)
test("Hello World!")

Result: Hello World!

Using Return

def test(var):
    Return var
print(test("Hello World!"))

Result:Hello World!

"when I can use print() and it gives me the same result" - **it does not**. It only looks like that in interactive mode because of interactive auto-printing. — user2357112, Jan 14 '23 at 17:33
Does this answer your question? [What is the purpose of the return statement? How is it different from printing?](https://stackoverflow.com/questions/7129285/what-is-the-purpose-of-the-return-statement-how-is-it-different-from-printing) — Sören, Jan 14 '23 at 18:09
You might check out the result of doing `def test3(var): return print(var)` and a `print(test3("Hello World!"))`. That might also help you see what is happening. — JonSG, Jan 14 '23 at 19:06

score 2 · Answer 1 · answered Jan 14 '23 at 18:11

The use case is that it is not always, rather rarely, a matter of outputting the result of a function to the console.

Imagine having a function to square a number:

def square(number):
    return number * number

If you would do it with print() you just output the result to the console, nothing more. Using return you have the result returned to where the function call came from so you can proceed using it for something.

For example now you want to add two squared numbers like: a² + b² Using the function we build earlier we could do:

number = square(a) + square(b)

This would not be possible if the square function would simply output the result to the console since then there is nothing returned we could add together.

And yes, i know you don't need a function to square a number, that's just an example to explain it.

@PouryaMamadi yes, you can use the result for more computations if you use return — Caridorc, Jan 15 '23 at 15:29

score 0 · Answer 2 · answered Jan 15 '23 at 04:21

The return statement should be used in scenarios where you want to process the results which are the output of your function. An example of this is the function getEvens which tries to return all the even numbers in a given list:

def getEvens(l):
    """
        The function takes a list as input and returns only even no.s of the list.
    """
    
    # Check if all elements are integers
    for i in l:
        if type(i) != int:
            return None  # return None if the list is invalid

    return [i for i in l if i%2 == 0]  # return filtered list

Here in the driver code, we are passing the input list to the getEvens function, depending upon the value function returns we output a customized message.

def main(l):

    functionOutput = getEvens(l)  # pass the input list to the getEvens function

    if functionOutput is None:
        # As the function returned none, the input validation failed
        print("Input list is invalid! Accepting only integers.")

    else:
        # function has returned some other value except None, so print the output
        print("Filtered List is", functionOutput)

If we consider some scenarios now

Case 1:

l = [1, 7, 8, 4, 19, 34]
main(l)
# output is: Filtered List is [8, 4, 34]

Case 2:

l = [1.05, 7, 8, 4.0, 19, 34]
main(l)
# output is: Input list is invalid! Accepting only integers.

Case 3:

l = [1, 7, 8, 4, "19", 34]
main(l)
# output is: Input list is invalid! Accepting only integers.

So the main thing to look out for here is we are using the output of the function for later processing, in this case taking a decision to customize the output message. A similar use-case is of function chaining where the output of 1st function will be an input to the 2nd one, and 2nd output will be input to the 3rd (this cycle may continue longer ;P).

score 0 · Answer 3 · answered Jan 15 '23 at 15:17

In this case yes print would do exactly the same thing, but its usually better to do a return statement so the code would be more readable then with print

For example if you have this code

some_random_function("I am a String!")

You wouldn't know what the function does without going and finding the definition, but with return

# with a variable
v = some_random_function("I am a String!")
print(v)

# without one
print(some_random_function("I am a String!"))

The code suddenly becomes much more readable because you know that the function returns something then prints it and maybe there is a case when you would need the functions output, but not print it.

I hope this helped

Python Return Use Cases

3 Answers3