
class Student(object):
    def __init__(self,name,score):
        self.__name = name
        self.__score = score
    def print_score(self):
        print('%s:%s' % (self.__name,self.__score))

    def get_name(self):
        return self.__name

    def get_score(self):
        return self.__score

    def set_score(self,score):
        if 0<= score<=100:
            self.__score = score
        else:
            raise ValueError('bad error')

    def get_grade(self):
        if self.__score >= 90:
            print('A')
        elif self.__score >= 60:
            print('B')
        else:
            print('C')






