```
grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]
def print_grades(grades):
for grade in grades:
print grade
def grades_sum(grades):
total = 0
for grade in grades:
total += grade
return total
def grades_average(grades):
sum_of_grades = grades_sum(grades)
average = sum_of_grades / float(len(grades))
return average
def grades_variance(scores):
average = grades_variance(scores)
variance= 0
for score in scores:
variance = float(grades_sum(grades)) - (grades_average(grades)) ** 2
variance / scores
return variance
print grades_variance(grades)
```

I get this error "Oops, try again. grades_variance([4, 2, 2, 0, 9, 7, 4, 8]) raised an error: maximum recursion depth exceeded"