Now that we have a function to print the grades, let’s create another function to compute the sum of all of the test grades.

This will be super-helpful when we need to compute the average score.

I know what you’re thinking, “let’s just use the built-in sum function!” The built-in function would work beautifully, but it would be too easy.

Computing the sum manually involves computing a rolling sum. As you loop through the list, add the current grade to a variable that keeps track of the total, let’s call that variable total.