Please help me on this

```

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=variance+((average - score) ** 2)

variance1=variance/len(scores)

return variance1

print grades_variance(grades)

def grades_std_deviation(variance):

return variance ** 0.5

variance=grades_variance(grades)

print grades_std_deviation(variance)

def print_all(grades):

print_grades(grades)

grade_sum(grades)

grades_average(grades)

grades_variance(grades)

grades_std_deviation(grades_variance(grades))

```

I am getting error