Review


#1



https://www.codecademy.com/en/courses/python-intermediate-en-7mgOa/2/3?curriculum_id=4f89dab3d788890003000096#

grades_std_deviation(1199.5555555555559) returned 18.2776094147 instead of the correct value 34.6346005543

Hi! I have no idea, why the standard deviation function isn't working properly... please help.


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+=(average-score)**2
        scores_variance=variance/len(scores)
    return scores_variance

print grades_variance(grades)
def grades_std_deviation(variance):
    variance=grades_variance(grades)
    return variance**0.5

print grades_std_deviation(variance)


print grades
print grades_sum(grades)
print grades_average(grades)
print grades_variance(grades)
print grades_std_deviation(grades)


#2

Start by doing it manually and see what you get so that you can determine whether it's your understanding of what's supposed to be done or the implementation thereof -- in so doing you'll be cutting the problem in about half and be in a better position to look for other things that can be ruled out or asked about

And then you can either read the instructions more carefully or look closer at what your code is doing, for example by adding print statements explaining what's being done step by step, allowing you to further narrow down what the problem is

You can also use print statements to only do part of the problem manually, allowing you to start or stop with some partial result that you can compare to what your program got


#3

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 += (average - score) ** 2
return variance / (len(scores))

def grades_std_deviation(variance):
return variance ** 0.5

variance = grades_variance(grades)

print grades_std_deviation(variance)
print grades
print grades_sum(grades)
print grades_average(grades)
print grades_variance(grades)
print grades_std_deviation(grades)

I have tried but the problem still persists


#4

Thanks guys. ionatan, i liked your approach in helping me to think more instead of just giving the answer lol

The problem was in "print grades_std_deviation(variance)" before the final printing sequence (it was part of a previous exercise though, don't know why this was a problem). I just erased that and it worked fine.


#5

If you change several things and see a different outcome, then you don't have enough information to say that only one of the changes was what made that difference. Maybe you didn't notice making other changes as well. You can easily verify this by starting over with the code you posted and making only that change


#6

I did verify bro, that was the only change i've made.
Edit: actually, instead of printing ''grades'' at the end i printed the ''print_grades'' function. That's all i changed from my original post.


#7

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