判断学生的成绩情况

import student
def main():
    listOfSt = list_St()
    display(listOfSt)

def list_St():
    listOfSt = []
    flag = 'Y'
    while flag == 'Y':
        name = raw_input("请输入名字：")
        grade = flag(input("请输入成绩："))
        choice = raw_input("请选择(L or P)")
        if choice.upper() == 'L':
            s = student.LevelSt(name, grade)
        else:
            s = student.PassSt(name, grade)
        listOfSt.append(s)
        flag = raw_input("继承?(y/n):").upper()
    return listOfSt

def display(listOfSt):
    print("\n 姓名 \t 等级")
    listOfSt.sort(key=lambda x:x.getName())
    for each in listOfSt:
        each.show()