student_scores = [75, 84, 66, 99, 51, 65]

def get_grade_stats(scores): 
    #calculate the arithmetic mean 
    mean = sum(scores)/len(scores)

#calculate the standard deviation 
 tmp = 0 
 for score in scores: 
     tmp += (score - mean ) **2 
     std_dev = (tmp/len(scores)) **0.5 

     #Package and return average, standard deciation in a tuple
     return mean, std_dev 

# unpack tuple 
average, standard_deviation = get_grade_stats(student_scores)

print(f'Average score: {average}')
print(f'Standard deviation: {standard_deviation}')


# the mean and standard deviation of a set of student test scores.
# The statement return mean, std_dev creates and returns a tuple container. Recall that a tuple doesn't require parentheses around the contents, 
# as the comma indicates a tuple should be created. 

# An equivalent statement would have been return (mean, std_dev). The outputs could also have been returned in a list, as in return [mean, std_dev]