1、如果为空，就打印消息“We need some users!”。
2、删除列表中的所有用户名，确定将打印正确的消息。
3、如果用户名为 'admin' ，就打印一条特殊的问候消息，如“Hello admin, would you like to see a status report?”。
4、否则，打印一条普通的问候消息，如“Hello sir, thank you for logging in again”。

# !/usr/bin/env python
# -*- coding:utf-8 -*-
方法一：
usrs = ['root','administrator','admin','ming','hong','guo']

if usrs:
    for usr in usrs:
        if usr == 'admin':
            print('Hello admin,would you like to see a report?')
        else:
            print('Hello sir,thank you for logging in again.')

else:
    print('we need some usrs.')

方法二：if len(usrs) == 0:
    print('we need some usrs.')
else:
    for usr in usrs:
        if usr == 'admin':
            print('Hello admin,would you like to see a report?')
        else:
            print('Hello sir,thank you for logging in again.')