Oops, try again. It looks like the standard deviation was not printed! Make sure you are printing it on its own line.

I've printed everything, yet the standard deviation doesn't show up on the console. Why is this so?

```
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:
b = (average - score) ** 2
variance = variance + b
result = variance / len(scores)
return result
print grades_variance(grades)
def grades_std_deviation(variance):
c= variance ** 0.5
return c
variance = grade_variance(grades)
print grades_std_deviation(variance)
print print_grades(grades)
print grades_sum(grades)
print grades_average(grades)
print grades_variance(grades)
print grades_std_deviation(variance)
```