题解 | 禁止重复注册

current_users=['Niuniu','Niumei','GURR','LOLO']
new_users=['GurR','Niu Ke Le','LoLo','Tuo Rui Chi']
current_users_lower = {user.lower() for user in current_users}
for new_user in new_users:
    if new_user.lower() in current_users_lower:
        print(f"The user name {new_user} has already been registered! Please change it and try again!")
    else:
        print(f"Congratulations, the user name {new_user} is available!")