8.19实验：足球球队花名册程序（字典）报错求助

作业要求 #

• 输入5组球员球衣号（0-99）和评分（1-9），存入字典并按球衣号升序输出花名册；
• 实现菜单功能，包含添加、删除、更新评分、输出指定评分以上球员、输出花名册、退出选项；
• 依次实现各菜单选项功能。

我的代码 #

Roster1={
    'player 1':[],
    'player 2':[],
    'player 3':[],
    'player 4':[],
    'player 5':[]
    }
for n in range(5):
    jersey=int(input("Enter player %s"%(n+1)+"'s jersey number:\n"))
    rating=int(input("Enter player %s"%(n+1)+"'s rating:\n\n"))
    Roster1[f"player {n+1}"]=(int(jersey),int(rating))

sorted_roster = dict(sorted(Roster1.items(), key=lambda x: x[1][0]))

userchoice=''    

print("ROSTER")
for player, (jersey, rating) in sorted_roster.items():
    print(f'Jersey number: {jersey}, Rating: {rating}')
print('')
print("MENU")
print("a - Add player")
print("d - Remove player")
print("u - Update player rating")
print("r - Output players above a rating")
print("o - Output roster")
print("q - Quit")
print('\nChoose an option:')

while userchoice != 'q':
    userchoice=str(input())
    
    if userchoice=='q':
        break
    elif userchoice=='o':
        print()
        print("ROSTER")
        for player, (jersey, rating) in sorted_roster.items():
            print(f'Jersey number: {jersey}, Rating: {rating}')
        continue
    elif userchoice=='a':
        addjersey=str(input("Enter a jersey number:\n"))
        addrate=str(input("Enter a new rating for player:\n"))
        sorted_roster["player 6"]=(addjersey,addrate)
        sorted_roster = dict(sorted(Roster1.items(), key=lambda x: x[1][0]))
        print("ROSTER")
        for player, (jersey, rating) in sorted_roster.items():
            print(f'Jersey number: {jersey}, Rating: {rating}')
        print('')
        print("MENU")
        print("a - Add player")
        print("d - Remove player")
        print("u - Update player rating")
        print("r - Output players above a rating")
        print("o - Output roster")
        print("q - Quit")
        print('\nChoose an option:')
    
    elif userchoice=='d':
        removejersey=int(input("Enter a jersey number:\n"))
        for player,(jersey,rating) in sorted_roster.items():
            if jersey==removejersey:
                del sorted_roster[player]
        print()
        for player, (jersey, rating) in sorted_roster.items():
            print(f'Jersey number: {jersey}, Rating: {rating}')
        print('')
        print("MENU")
        print("a - Add player")
        print("d - Remove player")
        print("u - Update player rating")
        print("r - Output players above a rating")
        print("o - Output roster")
        print("q - Quit")
        print('\nChoose an option:')
    elif userchoice=='r':
        above=int(input("Enter a rating\n"))
        print(f'ABOVE {above}')
        sorted_roster = dict(sorted(Roster1.items(), key=lambda x: x[1][0]))
        for player, (jersey, rating) in sorted_roster.items():
            if rating>above:
                print(f'Jersey number: {jersey}, Rating: {rating}')
        print('')
        print("MENU")
        print("a - Add player")
        print("d - Remove player")
        print("u - Update player rating")
        print("r - Output players above a rating")
        print("o - Output roster")
        print("q - Quit")
        print('\nChoose an option:')

报错情况 #

运行时错误：遍历字典期间字典大小发生变化（RuntimeError: dictionary changed size during iteration）

问题排查与修复方案 #

1. 核心报错原因 #

删除球员的代码中，直接遍历sorted_roster.items()并同时删除字典元素，Python不允许在遍历字典的同时修改其大小，因此触发RuntimeError。

2. 其他潜在问题 #

• 添加球员时，将新球员存入sorted_roster后又重新从Roster1排序，导致新添加的球员丢失（Roster1未同步更新）；同时球衣号和评分被存为字符串，后续排序、比较会触发类型错误。
• 输出指定评分以上球员时，重新从Roster1排序，会丢失之前的添加/删除操作结果。
• 未实现更新评分的功能。
• 球员命名硬编码（如player 6），多次添加会覆盖已有球员。

3. 修复后的完整代码 #

# 用球衣号作为字典键，便于查找、修改、删除操作
roster = {}

# 输入5组球员信息
for n in range(5):
    jersey = int(input(f"Enter player {n+1}'s jersey number:\n"))
    rating = int(input(f"Enter player {n+1}'s rating:\n\n"))
    roster[jersey] = rating

# 封装排序输出花名册的函数，避免重复代码
def print_roster():
    print("\nROSTER")
    # 按球衣号升序遍历输出
    for jersey in sorted(roster.keys()):
        print(f'Jersey number: {jersey}, Rating: {roster[jersey]}')

# 打印初始花名册
print_roster()

# 菜单循环
while True:
    print('\nMENU')
    print("a - Add player")
    print("d - Remove player")
    print("u - Update player rating")
    print("r - Output players above a rating")
    print("o - Output roster")
    print("q - Quit")
    choice = input('\nChoose an option: ').strip().lower()

    if choice == 'q':
        break
    elif choice == 'o':
        print_roster()
    elif choice == 'a':
        jersey = int(input("Enter a jersey number:\n"))
        rating = int(input("Enter a new rating for player:\n"))
        roster[jersey] = rating
        print_roster()
    elif choice == 'd':
        remove_jersey = int(input("Enter a jersey number:\n"))
        # 通过键直接判断并删除，避免遍历字典时修改其大小
        if remove_jersey in roster:
            del roster[remove_jersey]
        print_roster()
    elif choice == 'u':
        jersey = int(input("Enter a jersey number:\n"))
        if jersey in roster:
            new_rating = int(input("Enter a new rating:\n"))
            roster[jersey] = new_rating
        else:
            print("Player not found.")
        print_roster()
    elif choice == 'r':
        above_rating = int(input("Enter a rating:\n"))
        print(f"\nABOVE {above_rating}")
        for jersey in sorted(roster.keys()):
            if roster[jersey] > above_rating:
                print(f'Jersey number: {jersey}, Rating: {roster[jersey]}')
    else:
        print("Invalid option, please try again.")

修复说明 #

• 改用球衣号作为字典键，符合业务逻辑，查找、修改、删除操作更高效，无需遍历整个字典。
• 封装print_roster()函数，避免重复代码，保证输出始终按球衣号升序排列。
• 删除球员时直接通过键判断并删除，解决遍历字典时修改大小的RuntimeError。
• 统一将输入的球衣号和评分转为整数，避免类型错误。
• 修复添加球员时数据丢失的问题，直接更新主字典roster。
• 补充实现更新评分的功能。
• 增加无效输入提示，提升程序健壮性。

内容的提问来源于stack exchange，提问作者Grace Mcpadden