Python programming

courses=[]
students=[]
grades=[]

d=dict(A=10,AB=9,B=8,BC=7,C=6,CD=5,D=4,AA=0)

inp=input()

while True:
    if inp == 'Courses':
        inp = input()
        while inp != 'Students':
            courses.append(inp)
            inp = input()
    elif inp == 'Students':
        inp = input()
        while inp != 'Grades':
         
            students.append(inp)
            inp = input()

    elif inp == 'Grades':
        inp = input()
        while inp != 'EndOfInput':
            grades.append(inp)
            inp = input()
    elif inp == 'EndOfInput':
        break
    else:
        break



def split2(l):
  l=l.split('~')
  return l



s_courses=[]
s_students=[]
s_grades=[]

for item in courses:
  s_courses.append(split2(item))
for item in students:
  s_students.append(split2(item))
for item in grades:
  s_grades.append(split2(item))




for item in s_grades:
  item[-1]=d[item[-1]]

result=[]

for item in s_students:
  stu_grades_avg=0
  stu_grades_sum=0
  count=0

  for x in s_grades:
    if item[0]==x[3]:
      count=count+1
      stu_grades_sum=stu_grades_sum+x[-1]
      stu_grades_avg=round(stu_grades_sum/count,2)

  result.append([item[0],item[1],str(stu_grades_avg)])



def rn(l):
  return l[0]

result.sort(key=rn)

result1=[]

for item in result:
  z=('~').join(item)
  result1.append(z)


for item in result1:
  print (item)