Why Is My Python Function Returning None?

Why Is My Python Function Returning `None`?

You've reached a major milestone in your Python journey: writing your own functions. You're excited to organize your code into reusable blocks. You write your first function to add two numbers, and it seems to work perfectly:

Python
def add_numbers(a, b):
    result = a + b
    print(result)

# Let's test it!
add_numbers(5, 10)

You run the code, and the number 15 appears on your screen. Success!

But then you try to do something with that result. You try to save it to a variable to use later, and everything falls apart.

Python
# Let's save the result
sum_value = add_numbers(5, 10)

print("The saved value is:")
print(sum_value)

The output is deeply confusing:

15
The saved value is:
None

You clearly saw the number 15 printed. Where did it go? Why is your sum_value variable holding this strange None value? This isn't a bug; it's a vital distinction between displaying a value and delivering a value.

The Problem: A Display vs. a Delivery

The confusion between print and return is the most common conceptual hurdle when learning functions. Here’s the simple analogy to make it clear forever:

print() is a Display Screen: Think of print() as a television screen connected to your function. Its only job is to display information for a human to see. Your main program is completely blind to what's on that screen. It shows you the value, but it doesn't give that value back to your code.
return is a Delivery Person: Think of return as a delivery person. Its job is to take a value from inside the function and hand-deliver it back to the exact spot in your code that called the function. This is how you get data out of a function for your program to actually use.

The Code Explained

Let's look at your first function again. It had a display screen (print) but no delivery person (return).

Python
def add_and_print(a, b):
    # This function only DISPLAYS the result
    result = a + b
    print(result)

# You call the function, and it displays '15' on its screen.
sum_value = add_and_print(5, 10)

# But it never DELIVERED anything back. So, what's in the variable?
# By default, a function that doesn't deliver anything gives back 'None'.
print(sum_value) # Output: None

Now, let's rewrite the function with a delivery person (return):

Python
def add_and_return(a, b):
    # This function DELIVERS the result
    result = a + b
    return result

# You call the function and CATCH the delivered value in a variable.
sum_value = add_and_return(5, 10)

# Now, the variable actually holds the value.
print(sum_value) # Output: 15

A Simple Rule: When to Use `print` vs. `return`

Use print() when the entire purpose of your function is to show information to the user and you don't need that information for any further calculations in your code. (e.g., a function that prints a welcome message or a formatted report).
Use return when the purpose of your function is to calculate or produce a value that your main program needs to use for something else—like storing it in a variable, passing it to another function, or using it in an if statement.

Frequently Asked Questions (FAQs)

1. What happens if I have code after a return statement?

It will never be executed. The return statement immediately exits the function and delivers the value. Any code after it is unreachable.

2. Can a function have both print and return?

Yes! A function can print status updates for the user while it's working and then return the final result at the end. The return must be the last thing the function does.

3. Can I return more than one value from a function?

Yes, and it's a powerful feature of Python! You simply separate the values with a comma. Python will automatically package them into a tuple.

Python
def get_user_info():
    name = "Alice"
    age = 30
    return name, age # Returns a tuple ('Alice', 30)

user_data = get_user_info()
print(user_data[0]) # Output: Alice

Conclusion: You've Mastered the Flow of Data

The empty None value isn't an error; it's Python telling you that your function didn't make a delivery. By understanding the critical difference between print (displaying for humans) and return (delivering for your program), you have unlocked the true power of functions.

You can now build modular, reusable blocks of code that reliably pass data between each other, which is the foundation of all serious programming.

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