python列表中str实现大小写转换

current_users = ['Niuniu','Niumei','GURR','LOLO']
new_current_users = [x.lower() for x in current_users] #将原列表转换为全部小写的新列表
new_users = ['GurR','Niu Ke Le','LoLo','Tuo Rui Chi']
for x in new_users:
    if x.lower() in new_current_users:
        print('The user name %s has already been registered! Please change it and try again!' %(x))
    else:
        print('Congratulations, the user name %s is available!' %(x))

将原数组遍历小写之后写入新数组。