Whats wrong with my code? It seems that my code is correct to me but why i am having that kind of error even if it prints all the the value correctly?

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

Oops, try again. It looks like not all grades were printed! Make sure you are printing ech one on their own line.

output:

[100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]

1045.5

80.4230769231

334.071005917

18.2776094147

None

```
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):
variance = 0
for score in scores:
variance += (grades_average(scores) - score) ** 2
variance = variance / len(scores)
return variance
def grades_std_deviation(variance):
return variance ** 0.5
variance = grades_variance(grades)
print grades
print grades_sum(grades)
print grades_average(grades)
print grades_variance(grades)
print grades_std_deviation(variance)
```