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

the erro said File "python", line 29

```
variance=grades_variance(grades)
^
IndentationError: unindent does not match any outer indentation level
```