Return Statements and Return Values

What a Return Statement Does

When you call a function, the program jumps into that function and executes its code line by line. But what happens when the function finishes? How does the program know to stop running the function's code and go back to where it was called? The answer is the return statement. The return statement does two things at once: it breaks out of the function (stops executing any more code inside it), and it sends a value back to the place where the function was called. Without a return statement, your function still exits when it reaches the end, but it sends back a special value called None, which means nothingness.

How Return Values Flow Back to the Caller

When a return statement executes, it does not just disappear. The value you return travels back through the call and becomes the result of that function call. Think of it like this: when you call a function, you are asking it a question. The return statement is the function's answer. That answer can then be stored in a variable, printed, used in a calculation, or passed to another function. The key insight is that a function call can be used anywhere you would use a value.

Return Stops Execution Immediately

One of the most important things to understand about the return statement is that it stops the function right away. Any code after the return statement inside that function will never run. This is called early exit. This is useful when you want to stop processing and send back a result without running the rest of the function. For example, if you are searching for a value in a list and you find it, you can return immediately without checking the rest of the list.

Returning a Value Versus Returning Nothing

You can write a return statement in two ways. You can write return followed by a value, like return 42 or return name. This sends that value back to the caller. Or you can write return with nothing after it, like just return by itself. When you do this, the function still exits, but it returns None instead of a specific value. In fact, if you do not write any return statement at all, Python automatically adds an invisible return None at the very end of your function. This is why every function in Python always returns something, even if you did not explicitly write a return statement.

Worked Example: Finding the Maximum

def maximum(a, b):
    if a > b:
        return a
    else:
        return b

result = maximum(5, 8)
print(result)

8

Common Mistakes with Return Statements

• Forgetting to actually use the returned value

  The function returns 8, but if you do not store it in a variable or print it, the value is lost and you cannot use it

  Fix: Store the result in a variable (result = maximum(5, 8)) or print it directly (print(maximum(5, 8)))

• Writing code after a return statement inside the function

  The return statement exits the function immediately, so the print statement will never run

  Fix: Put any code that needs to run before the return statement, or remove the code after return if it is not needed

• Confusing return with print

  print() displays a value on the screen but does not send it back to the caller. The function still returns None

  Fix: Use return to send a value back to the caller; use print only if you want to display something on the screen

• Assuming a function without an explicit return statement returns 0

  Functions without an explicit return statement return None, not 0

  Fix: Remember that every function implicitly returns None unless you write your own return statement

Multiple Return Statements in One Function

A function can have more than one return statement. This is common when you have different conditions and want to return different values depending on which condition is true. When the function runs, it will execute the code line by line until it hits a return statement. At that moment, it exits and sends back the value from that specific return statement. The other return statements are never reached. This is why it is safe to have multiple return statements in different branches of an if/else structure.

def check_grade(score):
    if score >= 90:
        return "A"
    elif score >= 80:
        return "B"
    elif score >= 70:
        return "C"
    else:
        return "F"

grade = check_grade(85)
print(grade)

B

Practice: Trace the Execution

Key Takeaways

1. The return statement exits a function immediately and sends a value back to the caller. Any code after the return statement does not run.
2. A function can return a specific value (like return 42) or return nothing explicitly (just return), which sends back None.
3. Every function in Python implicitly returns None at the end if you do not write your own return statement.
4. The value returned by a function becomes the result of the function call and can be stored in a variable, printed, or used in calculations.
5. A function can have multiple return statements in different branches (if/else blocks). Only one will execute per function call, and it exits the function immediately.