直接上源代码吧。

# 利用文件设计一个学生管理系统

class Student(object):

    def __init__(self):
        self.db_name = 'student_db.txt'
        self.students = {
            '7120214132341': '吕不韦',
            '8120214134348': '李明',
            '9120214131249': '张岩',
            '3220214121340': '祁门',
            '2120214431341': '吴峰'
        }
        try:
            with open(self.db_name, 'rt', encoding='UTF-8') as file:
                self.students.clear()
                db_data = file.readlines()
                for line in db_data:
                    line = [item.strip() for item in line.split(':') if line]
                    self.students[line[0]] = line[1]
        except FileNotFoundError as e:
            print('未发现数据库，系统将创建新的数据文件。')
        self.update_db()

    def update_db(self):
        self.students_list = list(self.students.keys())
        # 一个不好的文件更新实现
        with open(self.db_name, 'wt', encoding='UTF-8') as file:
            for key, value in self.students.items():
                file.write(f'{key}: {value}\n')

    def menu(self) -> None:
        """管理系统的菜单"""
        option = [
            '欢迎进入学生管理系统',
            '1. 查询全部学生',
            '2. 查询特定学生',
            '3. 更新学生信息',
            '4. 插入新的学生',
            '5. 删除已有学生',
            '6. 清除全部学生',
            '7. 退出管理系统'
        ]
        for item in option:
            print('|', item.center(30, '-'), '|')
        while True:
            choice = input('请根据菜单输入操作序号：')
            if choice.isdigit():
                if choice == '1':
                    self.query_all_student()
                elif choice == '2':
                    self.query_one_student()
                elif choice == '3':
                    self.update_student()
                elif choice == '4':
                    self.insert_new_student()
                elif choice == '5':
                    self.remove_one_student()
                elif choice == '6':
                    self.remove_all_student()
                elif choice == '7':
                    break
                else:
                    print('请输入正确的序号。')
            else:
                print('请输入数字。')

    def query_all_student(self) -> bool:
        """查询全部学生"""
        if not self.students:
            print('学生信息库是空的')
            return False
        for num in range(len(self.students_list)):
            student_sno = self.students_list[num]
            student_name = self.students.get(self.students_list[num])
            print(f'{num+1} 学号: {student_sno}, 学名: {student_name}')
        return True

    def query_one_student(self, query_name='') -> bool:
        """查询特定学生"""
        if not query_name:
            query_name = input('请输入要查询的学生姓名: ')
            if not self.is_name_valid(query_name):
                return False
        for sno, name in self.students.items():
            if query_name == name:
                print(f'{sno}: {name}')
                return True
        print('查无此人。')
        return False

    def update_student(self) -> bool:
        """更新一个学生信息"""
        sno = input('请输入要修改的学号: ')
        name = input('请输入学生姓名: ')
        if self.is_sno_valid(sno) and self.is_name_valid(name):
            if self.students.get(sno):
                self.students[sno] = name
                return True
            else:
                print('查无此人。')
        return False

    def insert_new_student(self) -> bool:
        """插入新的学生"""
        name = input('请输入学生的姓名: ')
        sno = input('请输入学生的学号: ')
        if self.is_sno_valid(sno) and self.is_name_valid(name):
            if self.students.get(sno):
                print('该学号已经存在。')
                return False
            self.students[sno] = name
            self.update_db()
        return True

    def remove_one_student(self) -> bool:
        """删除一个学生"""
        remove_name = input('请输入要删除的学生姓名: ')
        remove_sno = ''
        for sno, name in self.students.items():
            if remove_name == name:
                remove_sno = sno
                break
        if remove_sno:
            self.students.pop(remove_sno)
            self.update_db()
            return True
        else:
            print('查无此人。')
            return False

    def remove_all_student(self) -> bool:
        """删除所有学生"""
        self.students.clear()
        self.update_db()
        if self.students:
            print('清除失败，请排查故障')
            return False
        print('清除成功')
        return True

    def is_name_valid(self, name: str) -> bool:
        """检查输入的姓名是否合法"""
        if not name:
            print('姓名不可为空')
            return False
        if len(name) > 100:
            print('输入的姓名太长')
            return False
        return True

    def is_sno_valid(self, sno) -> bool:
        if not sno.isdigit() or len(sno) < 5 or len(sno) > 20:
            print('学号只能是5-20位的数字')
            return False
        return True


if __name__ == '__main__':
    Student().menu()