Solutions

1. Basic Solution

This function is very simple: it takes two inputs a and b, adds them, and returns the result.

def add_two_numbers(a: int, b: int) -> int: return a + b

2. With variable

This version performs the same addition but introduces an intermediate variable, which we have named sum_result, to hold the sum before it's returned. This can sometimes improve readability for more complex calculations, although for simple addition like this, it adds an extra step.

def add_two_numbers_with_variable(a: int, b: int) -> int: # Calculate the sum and store it in a variable sum_result = a + b # Return the stored result return sum_result

Common mistakes

1. Forgetting the return statement

A very common mistake for beginners is to forget the return statement. For example:

def add_two_numbers(a: int, b: int) -> int: a + b # This does nothing!

In this version, Python evaluates a + b, but the result isn't stored or returned — so the function returns None by default. This would cause all your tests to fail, even though the logic looks correct.

2. Using print instead of return

Another common mistake is trying to print the result instead of returning it:

def add_two_numbers(a: int, b: int) -> int: print(a + b) # This prints the result but doesn't return it

This will show the right number on screen, but when used in code (like in a test or another function), the return value is still None.

Always remember: if a function is supposed to give you back a value, you must use return.