pyhthon 求GPA平均学分绩点

 #coding=utf-8
 '''
 北大4.0
 成绩    学分
 100～90    4.0
 89～85    3.7
 84～82    3.3
 81～78    3.0
 77～75    2.7
 74～72    2.3
 71～68    2.0
 67～64    1.5
 63～60    1.0
 59～0    0
 平均学分绩点=∑(课程学分×成绩绩点)/∑课程学分=各门课程学分绩点之和/各门课程学分数之和
 '''
 filename='./myscore.txt'
 list1=[]
 def cal():
     fr=open(filename)
     for line in fr.readlines():
         line1=line.strip("\n").split(",")
         # print(line1)
         a=float(line1[0])
         b=float(line1[1])
         if(a>=90):
             list1.append((a,(b,4.0)))
         if(a>=85 and a<=89):
             list1.append((a,(b,3.7)))
         if(a>=82 and a<=84):
             list1.append((a,(b,3.3)))
         if(a>=78 and a<=81):
             list1.append((a,(b,3.0)))
         if(a>=75 and a<=77):
             list1.append((a,(b,2.7)))
         if(a>=72 and a<=74):
             list1.append((a,(b,2.3)))
         if(a>=68 and a<=71):
             list1.append((a,(b,2.0)))
         if(a>=64 and a<=67):
             list1.append((a,(b,1.5)))
         if(a>=60 and a<=63):
             list1.append((a,(b,1.0)))
         if(a<60):
             list1.append((a,(b,0.0)))

     # print(list1)
     # print(list1.keys())
     # print(list1.values())
     c=list1
     sum_p=0
     sum_s=0
     # print(c)
     for i in range(len(c)):
         sum_p=sum_p+c[i][1][0]*c[i][1][1]
         sum_s=sum_s+c[i][1][0]
     # print(sum_p)
     # print(sum_s)
     result=sum_p/sum_s
     print("北大4.0(GPA):%.2f"%result)

 if __name__ == '__main__':
     cal()