一、为什么需要建立爬虫代理ip池

在众多的网站防爬措施中，有一种是根据ip的访问频率进行限制的，在某段时间内，当某个ip的访问量达到一定的阀值时，该ip会被拉黑、在一段时间内被禁止访问。

这种时候，可以通过降低爬虫的频率，或者更改ip来应对。后者就需要有一个可用的代理ip池，以供爬虫工作时切换。

二、如何建立一个爬虫代理ip池

思路：

1、找到一个免费的ip代理网站(如：西刺代理)

2、爬取ip（常规爬取requests+BeautifulSoup）

3、验证ip有效性（携带爬取到的ip，去访问指定的url，看返回的状态码是不是200）

4、记录ip （写到文档）

代码如下：

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import requests,threading,datetime
from bs4 import BeautifulSoup
import random"""
1、抓取西刺代理网站的代理ip
2、并根据指定的目标url,对抓取到ip的有效性进行验证
3、最后存到指定的path
"""# ------------------------------------------------------文档处理--------------------------------------------------------
# 写入文档
def write(path,text):with open(path,'a', encoding='utf-8') as f:f.writelines(text)f.write('\n')
# 清空文档
def truncatefile(path):with open(path, 'w', encoding='utf-8') as f:f.truncate()
# 读取文档
def read(path):with open(path, 'r', encoding='utf-8') as f:txt = []for s in f.readlines():txt.append(s.strip())return txt
# ----------------------------------------------------------------------------------------------------------------------
# 计算时间差,格式: 时分秒
def gettimediff(start,end):seconds = (end - start).secondsm, s = divmod(seconds, 60)h, m = divmod(m, 60)diff = ("%02d:%02d:%02d" % (h, m, s))return diff
# ----------------------------------------------------------------------------------------------------------------------
# 返回一个随机的请求头 headers
def getheaders():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"]UserAgent=random.choice(user_agent_list)headers = {'User-Agent': UserAgent}return headers
# -----------------------------------------------------检查ip是否可用----------------------------------------------------
def checkip(targeturl,ip):headers =getheaders()  # 定制请求头proxies = {"http": "http://"+ip, "https": "http://"+ip}  # 代理iptry:response=requests.get(url=targeturl,proxies=proxies,headers=headers,timeout=5).status_codeif response == 200 :return Trueelse:return Falseexcept:return False#-------------------------------------------------------获取代理方法----------------------------------------------------
# 免费代理 XiciDaili
def findip(type,pagenum,targeturl,path): # ip类型,页码,目标url,存放ip的路径list={'1': 'http://www.xicidaili.com/nt/', # xicidaili国内普通代理'2': 'http://www.xicidaili.com/nn/', # xicidaili国内高匿代理'3': 'http://www.xicidaili.com/wn/', # xicidaili国内https代理'4': 'http://www.xicidaili.com/wt/'} # xicidaili国外http代理url=list[str(type)]+str(pagenum) # 配置urlheaders = getheaders() # 定制请求头html=requests.get(url=url,headers=headers,timeout = 5).textsoup=BeautifulSoup(html,'lxml')all=soup.find_all('tr',class_='odd')for i in all:t=i.find_all('td')ip=t[1].text+':'+t[2].textis_avail = checkip(targeturl,ip)if is_avail == True:write(path=path,text=ip)print(ip)#-----------------------------------------------------多线程抓取ip入口---------------------------------------------------
def getip(targeturl,path):truncatefile(path) # 爬取前清空文档start = datetime.datetime.now() # 开始时间threads=[]for type in range(4):   # 四种类型ip,每种类型取前三页,共12条线程for pagenum in range(3):t=threading.Thread(target=findip,args=(type+1,pagenum+1,targeturl,path))threads.append(t)print('开始爬取代理ip')for s in threads: # 开启多线程爬取s.start()for e in threads: # 等待所有线程结束e.join()print('爬取完成')end = datetime.datetime.now() # 结束时间diff = gettimediff(start, end)  # 计算耗时ips = read(path)  # 读取爬到的ip数量print('一共爬取代理ip: %s 个,共耗时: %s \n' % (len(ips), diff))#-------------------------------------------------------启动-----------------------------------------------------------
if __name__ == '__main__':path = 'ip.txt' # 存放爬取ip的文档pathtargeturl = 'http://www.cnblogs.com/TurboWay/' # 验证ip有效性的指定urlgetip(targeturl,path)

结果：