How can I ensure I’m printing everything properly?

Frequently Asked Questions Python FAQ
1

Question

How can I ensure I’m printing everything properly?

Answer

In this last exercise, Review, we are not creating any new functionality in our program. We’re simply calling all of the functions we’ve built to this point so we can see the output!
When using print_grades(), pass it the grades list, and there’s no need to write print before it because that’s what the function does inside already.
From the previous lessons, you should already have the variance and standard deviation printed out, so all that’s left is printing the sum and average by using the corresponding functions.
If you didn’t yet, be sure to define variance outside of any functions and set it to grades_variance(grades). Having that variable allows us to pass it to our grades_std_deviation() function.

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2 
grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]

def print_grades(grades_input):
  for grade in grades_input:
    print grade,

def grades_sum(scores):
  total = 0
  for score in scores: 
    total += score
  return total
    
def grades_average(grades_input):
  sum_of_grades = grades_sum(grades_input)
  average = sum_of_grades / float(len(grades_input))
  return average

def grades_variance(scores):
  average = grades_average(scores)
  variance = 0
  for score in scores:
    variance += (average-score) ** 2
  total_variance = variance/float(len(scores))
  return total_variance

def grades_std_deviation(variance):
  return variance ** 0.5

variance = grades_variance(grades)

print_grades(grades)
print
print "The sum of grades is %d" % grades_sum(grades)
print                                            
print "The average of grades is %d" % grades_average(grades)     
print
print "The variance of grades is %d" % grades_variance(grades)
print
print "The standard deviation of grades is %d" % grades_std_deviation(variance)

It says ‘sum of grades was not printed’ even though it was. What am I doing wrong?

3

Unfortunately you can’t really do so :joy:

Please print the numbers directly first:

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

Then do whatever formatting you want afterwards.

Have a good day.

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4

Man, why doesn’t Codecademy use modern python syntax -_-

print(print_grades(grades))
5

It is not that Codecademy not using modern syntax. It is purely because the course in question was built on Python 2. For modern syntax please check out the new Python 3 course.

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6

Oof, okay then. Thanks for telling me :slight_smile:

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7

Thank you, my friends.

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8

with the below code :grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]

def print_grades(grades_input):
for grade in grades_input:
print grade

def grades_sum(scores):
total = 0
for score in scores:
total += score
return total

def grades_average(grades_input):
sum_of_grades = grades_sum(grades_input)
average = sum_of_grades / float(len(grades_input))
return average

def grades_variance(scores):
average = grades_average(scores)
variance = 0
for score in scores:
variance += (average-score)**2
return variance/float(len(scores))

def grades_std_deviation(variance):
return variance**0.5

variance = grades_variance(grades)
print “Grades:”,print_grades(grades)
print “Sum of Grades:”,grades_sum(grades)
print “average grade:”,grades_average(grades)
print “variance:”,grades_variance(grades)
print "standard deviation: ",grades_std_deviation(variance)

I am getting ‘none’ in the output window while printing grades, is this expected or I am doing something wrong here.
Please help me with this.
Output Screen:
image
Please

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9

I have same result @siva.mnr. Have you solved the issue yet? After hours of research I still don’t know why?? Anybody please???

10

The function print_grades() prints a column of grades as it executes, but it has no return statement. In Python, very function lacking a return statement returns the value None.
So, when you call

print “Grades:”,print_grades(grades)

… the print statement prints what it sees, from left to right. First, it prints the string, “Grades”

Next, it comes to the function, print_grades(), so it must execute that function, and print the returned value.

During execution, a column of grades is printed, as we have seen.

But the function returns None, which is exactly what the print statement prints.

Remember, in Python, we print what we want to see on the screen
… but we return what Python needs to use, be it to assign to a variable, pass to a function, or place within a print statement.

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11

Cool, thank you. Getting a better understanding slowly but this explanation helps greatly.
Thanks again and have fun coding! :stuck_out_tongue_winking_eye:

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