current_users = ['ergou','Tiezhu','Shitou','admin','erya']
new_users = ['Ergou','xiaofeng','shitou','shuanzi','dongzi']
linshi = []  #临时储存全部小写current_users里的元素

#小写的current_users里的元素
for name in current_users:
    linshi.append(name.lower())
for name in new_users:
    if name.lower() in linshi:
        print(name + "已被使用，请输入别的用户名！！")
    else:
        print(name + "该用户名未被使用！！")
print("\n")