7. The variance
It passed me for the lesson but it prints None when I " print grades_variance(grades)"
I expect the variance to be a number.
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 i in scores: variance+=(average-i)**2 variance=variance/len(scores) return variance print grades_variance(grades)