rades = [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):

average = grades_sum(grades) / float(len(grades))

return average

def grades_variance(scores):

average = grades_average(scores)

variance = 0

for score in scores:

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

variance = variance / float(len(scores))

return variance

def grades_std_deviation(variance):

return variance ** 0.5

variance = grades_variance(grades)

print "The class grades are:"

print print_grades(grades)

print "The sum of all grades in the class is", grades_sum(grades)

print "The class average is", grades_average(grades)

print "The grade variance is", grades_variance(grades)

print "Standard deviation is", grades_std_deviation(variance)