if score >= 90 :

return 'A'

elif score >= 80 :

return 'B'

elif score >= 70 :

return 'C'

elif score >= 60 :

return 'D'

else :

# indent to arrange this message right in the middle of the chart top

print(" Grade Distribution")

# a set of hash keys use for query operation

grades = ('A', 'B', 'C', 'D', 'E', 'F')

for letter in grades:

print(" |")

print(letter + " +", end = "")

# here, individual "key" act as an index into hash table to get corresponding "value"

# (count for that "key" category)

count = instanceHist.getCount(letter)

# multiply single asterisk by number we get multiple asterisk that visually represent

# the appear frequency of a specific letter grade category

print("*" * count)

print(" |")

print( " +-----+-----+-----+-----+-----+-----+-----+-----" )

instanceHistogram = Histogram("ABCDF")

dataset = open('score_transcript.txt', "r")

for each_line in dataset:

letter_grade = scoreToLetterGrade(int(each_line))

instanceHistogram.increaseCount(letter_grade)

# when for loop exit, the five category have finished their statistic, ready for subsequently display