题解 | #牛牛的绩点#

绩点与等级的对应关系 = {
    'A': 4.0,
    'B': 3.0,
    'C': 2.0,
    'D': 1.0,
    'F': 0
}

sum_grade = 0
sum_credit = 0

while True:
    # 输入等级
    grade = input()
    if grade.lower() == 'false':
        break

    # 输入学分
    credit = int(input())
    sum_grade += credit * 绩点与等级的对应关系[grade]
    sum_credit += credit

# 计算平均绩点
average_grade = sum_grade / sum_credit

print('%.2f' % average_grade)