Traceback (most recent call last):

File "python", line 30, in

NameError: name 'variance' is not defined

I included the variable, but it looks like the variance is not defined?

```
def grades_std_deviation(variance):
variance = grades_variance(grades)
result = 0
for grades in result:
variance = variance ** 0.5
variance = variance / float(len(result))
return result
print grades_std_deviation(variance)
```