题解 | #禁止重复注册#

current_users=['Niuniu','Niumei','GURR','LOLO']
current_users_up=[i.upper() for i in current_users] #将各元素先统一大写，复制给一临时列表
new_users=['GurR','Niu Ke Le','LoLo','Tuo Rui Chi']

for i in range(len(new_users)):
    if new_users[i].upper() in current_users_up:
        print(f'The user name {new_users[i]} has already been registered! Please change it and try again!')
    else:
        print(f'Congratulations, the user name {new_users[i]} is available!')