题解 | #禁止重复注册#

current_users=['Niuniu','Niumei','GURR','LOLO']
new_users=['GurR','Niu Ke Le','LoLo','Tuo Rui Chi']
for x in new_users:
    for y in current_users:
        if x.lower()==y.lower():
            print('The user name %s has already been registered! Please change it and try again!'%x)
            break
    else:
        print('Congratulations, the user name %s is available!'%x)
#嵌套循环