1.写一个程序

a.用一个变量来保存一个班级的学生信息，学生信息:姓名、学号、成绩(英语、体育、美术、数学)、年龄
b.可以给这个班级添加学生
c.根据姓名查看班级里的某个学生的信息
d.根据姓名删除一个指定的学生信息
e.查看班级所有的学生的信息
f.求指定学生的平均成绩

import os


def screen_clear():
    os.system('cls')


# 定义一个列表来保存学生信息
stu_info = [{'name':'joe', 'stu_id':'py1805001', 'score':{'English':'80', 'PE':'70', 'art':'75', 'math':'85'}, 'age':'22'},
            {'name':'re', 'stu_id':'py1805002', 'score':{'English':'81', 'PE':'71', 'art':'76', 'math':'86'}, 'age':'21'}]
eye = False
while True:
    # 清屏
    screen_clear()
    # 打印信息
    print('''
    欢迎来到学生信息系统！
    1.添加学生信息
    2.根据学号查看个人信息
    3.根据学号删除一个指定的学生信息
    4.查看所有学生的信息
    5.求指定学号的学生的平均成绩
    输入"exit"退出程序
    ''')

    # 用户输入
    user_cmd = input('>>>>>')
    if user_cmd == '1':
        # 清屏
        screen_clear()
        stu_id_new = input('请输入学生的学号:')
        for index_info in range(len(stu_info)):
            if stu_id_new in stu_info[index_info]['stu_id']:
                print('该学生信息已存在！')
                eye = True
                break
        if eye:
            continue


        name_new = input('请输入学生的姓名：')
        score_new_english = input('请输入音乐成绩：')
        score_new_pe = input('请输入体育成绩：')
        score_new_art = input('请输入美术成绩：')
        score_new_math = input('请输入数学成绩：')
        age_new = input('请输入学生的年龄：')

        # 插入数据
        stu_info.append({'name':name_new, 'stu_id':stu_id_new,
                         'score':{'English':score_new_english, 'PE':score_new_pe, 'art':score_new_art, 'math':score_new_math},
                         'age':age_new})

    elif user_cmd == '2':
        stu_id_retrieve = input('请输入学生的学号:')
        for index_info in range(len(stu_info)):
            # 查找学生
            if stu_id_retrieve in stu_info[index_info]['stu_id']:
                # 清屏
                screen_clear()
                # 打印学生信息
                print('姓名:%s\t学号:%s\t英语:%s\t体育:%s\t美术:%s\t数学:%s\t年龄:%s\t'%(stu_info[index_info]['name'],
                      stu_info[index_info]['stu_id'],stu_info[index_info]['score']['English'],
                      stu_info[index_info]['score']['PE'],stu_info[index_info]['score']['art'],
                      stu_info[index_info]['score']['math'],stu_info[index_info]['age'] ))
                break
            elif not stu_id_retrieve in stu_info[index_info]['stu_id']:
                print('不存在该学生！')

    elif user_cmd == '3':
        stu_id_del = input('请输入学生的学号:')
        for index_info in range(len(stu_info)):
            # 查找学生
            if stu_id_del in stu_info[index_info]['stu_id']:
                del stu_info[index_info]
                print('删除信息成功！')
                break

    elif user_cmd == '4':
        for index_info in range(len(stu_info)):
            print('姓名:%s\t学号:%s\t英语:%s\t体育:%s\t美术:%s\t数学:%s\t年龄:%s\t' % (stu_info[index_info]['name'],
                    stu_info[index_info]['stu_id'],stu_info[index_info]['score']['English'],
                    stu_info[index_info]['score']['PE'],stu_info[index_info]['score']['art'],
                    stu_info[index_info]['score']['math'],stu_info[index_info]['age']))

    elif user_cmd == '5':
        stu_id_ave = input('请输入学生的学号:')
        for index_info in range(len(stu_info)):
            # 查找学生
            if stu_id_ave in stu_info[index_info]['stu_id']:
                score_ave = (int(stu_info[index_info]['score']['English'])+int(stu_info[index_info]['score']['PE'])
                            +int(stu_info[index_info]['score']['art'])+int(stu_info[index_info]['score']['math']))/4

                print('姓名:%s\t学号:%s\t平均成绩是:%d'%(stu_info[index_info]['name'],
                                                stu_info[index_info]['stu_id'],score_ave))
    elif user_cmd == 'exit':
        break
    else:
        print('输入内容有误！')

2.学生管理系统

stu_infos = [{'name':'joe', 'stu_id':'py1805001', 'score':{'English':'80', 'PE':'70', 'art':'75', 'math':'85'},
              'age':'22'},
            {'name':'re', 'stu_id':'py1805002', 'score':{'English':'81', 'PE':'71', 'art':'76', 'math':'86'},
             'age':'21'}]

def list_main():
    print('''
        欢迎来到学生信息系统！
        1.添加学生信息
        2.根据学号查看个人信息
        3.根据学号删除一个指定的学生信息
        4.查看所有学生的信息
        5.求指定学号的学生的平均成绩
        输入"exit"退出程序
        ''')
    user_cmd = input('>>>>>')
    return user_cmd


# 判断用户输入
def user_input(user_cmd):
    if user_cmd == '1':
        stu_info = stu_find()
        if not isinstance(stu_info, str):
            print('该学生信息已存在！')
            return
        name, stu_id, english, pe, art, math, age = stu_info_input(stu_info)
        stu_create(name, stu_id, english, pe, art, math, age)
        # 判断是否继续或者退出
        flag = '1'
        redo(flag)

    elif user_cmd == '2':
        stu_info = stu_find()
        if isinstance(stu_info, str):
            print('学生信息不存在！')
        else:
            # 打印学生信息
            print('姓名:%s\t学号:%s\t英语:%s\t体育:%s\t美术:%s\t数学:%s\t年龄:%s\t' % (stu_info['name'],
                stu_info['stu_id'],stu_info['score']['English'],stu_info['score']['PE'],
                stu_info['score']['art'],stu_info['score']['math'],stu_info['age']))
            # 判断是否继续或者退出
            flag = '2'
            redo(flag)

    elif user_cmd == '3':
        stu_info = stu_find()
        if isinstance(stu_info, str):
            print('学生信息不存在！')
        else:
            stu_del(stu_info)
            # 判断是否继续或者退出
            flag = '3'
            redo(flag)

    elif user_cmd == '4':
        stu_find_all()
        # 判断是否继续或者退出
        flag = '4'
        redo(flag)

    elif user_cmd == '5':
        stu_info = stu_find()
        if isinstance(stu_info, str):
            print('学生信息不存在！')
        else:
            score_ave(stu_info)
            # 判断是否继续或者退出
            flag = '5'
            redo(flag)

    elif user_cmd == 'exit':
        exit(0)
    else:
        print('输入内容有误！')




# 查找学生
def stu_find():
    stu_info = input('请输入学生的学号:')
    for index_info in range(len(stu_infos)):
        # 学生信息存在
        if stu_info == stu_infos[index_info]['stu_id']:
            return stu_infos[index_info]
        # 学生信息不存在
    return stu_info



# 查找全部
def stu_find_all():
    for index_info in range(len(stu_infos)):
        print('姓名:%s\t学号:%s\t英语:%s\t体育:%s\t美术:%s\t数学:%s\t年龄:%s\t' % (stu_infos[index_info]['name'],
                                                                     stu_infos[index_info]['stu_id'],
                                                                     stu_infos[index_info]['score']['English'],
                                                                     stu_infos[index_info]['score']['PE'],
                                                                     stu_infos[index_info]['score']['art'],
                                                                     stu_infos[index_info]['score']['math'],
                                                                     stu_infos[index_info]['age']))

# 用户输入学生信息
def stu_info_input(stu_info):
    stu_id = stu_info
    name = input('请输入学生的姓名：')
    english = input('请输入音乐成绩：')
    pe = input('请输入体育成绩：')
    art = input('请输入美术成绩：')
    math = input('请输入数学成绩：')
    age = input('请输入学生的年龄：')
    return name, stu_id, english, pe, art, math, age


# 添加学生信息
def stu_create(name, stu_id, english, pe, art, math, age):
    stu_infos.append({'name':name, 'stu_id':stu_id,'score':{'English':english, 'PE':pe, 'art':art, 'math':math},
                      'age':age})


# 删除学生信息
def stu_del(stu_info):
    index_stu = stu_infos.index(stu_info)
    del stu_infos[index_stu]
    print('删除信息成功！')


# 平均成绩
def score_ave(stu_info):
    score_ave = (int(stu_info['score']['English']) + int(stu_info['score']['PE'])
                 + int(stu_info['score']['art']) + int(stu_info['score']['math'])) / 4

    print('姓名:%s\t学号:%s\t平均成绩是:%d' % (stu_info['name'],
                                      stu_info['stu_id'], score_ave))


#
def redo(flag):
    if flag =='1':
        user_cmd = input('''
                1.继续添加
                2.返回上一层
                >>>>>
                ''')
        if user_cmd == '1':
            user_input(flag)
        elif user_cmd == '2':
            return
        else:
            print('输入有误!')

    elif flag == '2':
        user_cmd = input('''
                1.继续查看
                2.返回上一层
                >>>>>
                ''')
        if user_cmd == '1':
            user_input(flag)
        elif user_cmd == '2':
            return
        else:
            print('输入有误!')

    elif flag == '3':
        user_cmd = input('''
                1.继续删除
                2.返回上一层
                >>>>>
                ''')
        if user_cmd == '1':
            user_input(flag)
        elif user_cmd == '2':
            return
        else:
            print('输入有误!')
    elif flag == '4':
        user_cmd = input('''
                1.继续查看
                2.返回上一层
                >>>>>
                ''')
        if user_cmd == '1':
            user_input(flag)
        elif user_cmd == '2':
            return
        else:
            print('输入有误!')

    elif flag == '5':
        user_cmd = input('''
                1.继续查询
                2.返回上一层
                >>>>>''')
        if user_cmd == '1':
            user_input(flag)
        elif user_cmd == '2':
            return
        else:
            print('输入有误!')


# 主程序
def main():
    while True:
        # 打印列表内容，等待用户输入
        user_input(list_main())


# 开始程序
if __name__ == '__main__':
    main()

ps:变着花样的CRUD