题解 | #禁止重复注册#

current_users = ['Niuniu', 'Niumei', 'GurR', 'LOLO']
new_users = ['GurR', 'Niu Ke Le', 'LoLo', 'Tuo Rui Chi']
#新列表，将字母全部转换成小写
current_users_up = [_.lower() for _ in current_users]

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