题解 | #牛牛的绩点#

class_score = {"A":4.0,"B":3.0,"C":2.0,"D":1.0,"F":0} #键值对存储在字典内
class_list = [] #等级列表
score_list = [] #学分列表
while True:
    a = input()
    if a == 'False':
        break
    else:
        b = input()
        class_list.append(a)
        score_list.append(b)
sum_score = 0 #总学分绩
total_score = 0 #总学分
for i in range(len(score_list)):
    sum_score += int(score_list[i])*int(class_score[class_list[i]])
    total_score += int(score_list[i])
print('%.2f'%(sum_score/total_score))