为自己的爬虫更换代理和HTML头部

import requests
import re
import random
import time

class download():

def __init__(self):

self.iplist = [] ##初始化一个list用来存放我们获取到的IP
html = requests.get("http://haoip.cc/tiqu.htm") ##不解释咯
iplistn = re.findall(r'r/>(.*?)<b', html.text, re.S) ##表示从html.text中获取所有r/><b中的内容，re.S的意思是包括匹配包括换行符，findall返回的是个list哦！
for ip in iplistn:
i = re.sub('\n', '', ip) ##re.sub 是re模块替换的方法，这儿表示将\n替换为空
self.iplist.append(i.strip()) ##添加到我们上面初始化的list里面

self.user_agent_list = [
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/22.0.1207.1 Safari/537.1",
"Mozilla/5.0 (X11; CrOS i686 2268.111.0) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.57 Safari/536.11",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.6 (KHTML, like Gecko) Chrome/20.0.1092.0 Safari/536.6",
"Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.6 (KHTML, like Gecko) Chrome/20.0.1090.0 Safari/536.6",
"Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/19.77.34.5 Safari/537.1",
"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.9 Safari/536.5",
"Mozilla/5.0 (Windows NT 6.0) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.36 Safari/536.5",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
"Mozilla/5.0 (Windows NT 5.1) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_0) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1063.0 Safari/536.3",
"Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1062.0 Safari/536.3",
"Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
"Mozilla/5.0 (Windows NT 6.1) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1061.1 Safari/536.3",
"Mozilla/5.0 (Windows NT 6.2) AppleWebKit/536.3 (KHTML, like Gecko) Chrome/19.0.1061.0 Safari/536.3",
"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/535.24 (KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24",
"Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/535.24 (KHTML, like Gecko) Chrome/19.0.1055.1 Safari/535.24"
]

def get(self, url, timeout, proxy=None, num_retries=6): ##给函数一个默认参数proxy为空
UA = random.choice(self.user_agent_list) ##从self.user_agent_list中随机取出一个字符串
headers = {'User-Agent': UA} ##构造成一个完整的User-Agent （UA代表的是上面随机取出来的字符串哦）

if proxy == None: ##当代理为空时，不使用代理获取response（别忘了response啥哦！之前说过了！！）
try:
return requests.get(url, headers=headers, timeout=timeout)##这样服务器就会以为我们是真的浏览器了
except:##如过上面的代码执行报错则执行下面的代码

if num_retries > 0: ##num_retries是我们限定的重试次数
time.sleep(10) ##延迟十秒
print(u'获取网页出错，10S后将获取倒数第：', num_retries, u'次')
return self.get(url, timeout, num_retries-1) ##调用自身 并将次数减1
else:
print(u'开始使用代理')
time.sleep(10)
IP = ''.join(str(random.choice(self.iplist)).strip()) ##下面有解释哦
proxy = {'http': IP}
return self.get(url, timeout, proxy,) ##代理不为空的时候

else: ##当代理不为空
try:
IP = ''.join(str(random.choice(self.iplist)).strip()) ##将从self.iplist中获取的字符串处理成我们需要的格式（处理了些什么自己看哦，这是基础呢）
proxy = {'http': IP} ##构造成一个代理
return requests.get(url, headers=headers, proxies=proxy, timeout=timeout) ##使用代理获取response
except:

if num_retries > 0:
time.sleep(10)
IP = ''.join(str(random.choice(self.iplist)).strip())
proxy = {'http': IP}
print(u'正在更换代理，10S后将重新获取倒数第', num_retries, u'次')
print(u'当前代理是：', proxy)
return self.get(url, timeout, proxy, num_retries - 1)
else:
print(u'代理也不好使了！取消代理')
return self.get(url, 3)

request = download() ##