Exam statistics exercise: https://www.codecademy.com/courses/python-intermediate-en-7mgOa/2/3?curriculum_id=4f89dab3d788890003000096#

Despite the sum being printed, I repeatedly get an error message stating that it has not been printed I found a similar topic onthis forum, but I still cannot see where the mistake is. Thanks in advance

```
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_average(scores)
variance = 0
for score in scores:
variance += (average - score)**2
variance = variance / float(len(scores))
return variance
#print grades_variance(grades)
def grades_std_deviation(variance):
return variance ** 0.5
variance = grades_variance(grades)
#print grades_std_deviation(variance)
print "The grades: "
print_grades(grades)
#print
print "sum of grades: %s" % grades_sum(grades)
#print
print "Average: %d" % grades_average(grades)
print "Variance: %d" % grades_variance(grades)
print "Standard dev: %d" % grades_std_deviation(grades_variance(grades))
```