from math import sqrt

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 / len(grades)

return average

def grades_variance(scores, average):

variance = 0

for each in scores:

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

a = (variance / len(scores))

return a

def grades_std_deviation(variance):

var = grades_variance(grades, grades_average(grades))

std_dev = sqrt(var)

return std_dev

print print_grades(grades)

print grades_sum(grades)

print grades_average(grades)

print grades_variance(grades, grades_average(grades))

print grades_std_deviation(grades_variance(grades, grades_average(grades)))