NP24 禁止重复注册

思路：

step1：创建两个列表；

step2：将cur列表转化为小写字母形式；

step3：遍历new_列表，对应要求，分别打印输出；

代码如下：

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