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):

#float total

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

print print_grades(grades)

print "============="

print grades_sum(grades)

print "============="

print grades_average(grades)

def grades_variance(grades):

average = grades_average(grades)

print "\tAverage:\t" + str(average)

print "=1=========="

variance = 0

for n in grades:

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

# print variance

```
print "=2=========="
print "\tvariance:\t" + str(float(variance) / len(grades))
print "=3=========="
```

return float(variance) / len(grades)

# print grades_variance(grades)

def grades_std_deviation(grades):

variance = grades_variance(grades)

# print grades_variance(grades)

print "=4= The std_deviation is:"

return variance **0.5

print grades_std_deviation(grades)

def grades_std_deviation(grades):

variance = grades_variance(grades)

return variance **0.5

print grades_std_deviation(grades)