What is wring with this ? It computes the right answer. ( I know it is more complicated than it has to be)

def grades_sum(scores):

total=0

index=0

for i in range(len(grades)):

total= total + grades[index]

index+=1

return total

print grades_sum(grades)

gives this error message: Oops, try again. It looks like your grades_sum function doesn't properly compute the sum of all the grades! It returned 1045.5 instead of 10 for grades_sum([10])