Python之如何应对初级的反爬机制

分手后的思念是犯贱 2022-03-21 08:00 446阅读 0赞

爬虫是模拟人的浏览访问行为，进行数据的批量抓取。当抓取的数据量逐渐增大时，会给被访问的服务器造成很大的压力，甚至有可能崩溃。  
为了抵制爬虫，网站服务器会通过检查连接的useragent，来识别到底是浏览器访问还是代码访问的。如果是代码访问的，访问频率超过阈值，就会被封IP。  
面对这种初级反爬机制，我们可以采取三种策略去解决：  
**1.构造请求头**  
在Request headers中构造浏览器的请求头，模仿是浏览器在请求，下面的请求头随便选一个即可。

ua_list = [
    	"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.95 Safari/537.36 OPR/26.0.1656.60",
            "Opera/8.0 (Windows NT 5.1; U; en)",
            "Mozilla/5.0 (Windows NT 5.1; U; en; rv:1.8.1) Gecko/20061208 Firefox/2.0.0 Opera 9.50",
            "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; en) Opera 9.50",
            "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0",
            "Mozilla/5.0 (X11; U; Linux x86_64; zh-CN; rv:1.9.2.10) Gecko/20100922 Ubuntu/10.10 (maverick) Firefox/3.6.10",
            "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/534.57.2 (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2 ",
            "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.71 Safari/537.36",
            "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11",
            "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.133 Safari/534.16",
            "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.101 Safari/537.36",
            "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko",
            "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.11 TaoBrowser/2.0 Safari/536.11",
            "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.71 Safari/537.1 LBBROWSER",
            "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; LBBROWSER)",
            "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E; LBBROWSER)",
            "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; QQBrowser/7.0.3698.400)",
            "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 732; .NET4.0C; .NET4.0E)",
            "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.84 Safari/535.11 SE 2.X MetaSr 1.0",
            "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; SV1; QQDownload 732; .NET4.0C; .NET4.0E; SE 2.X MetaSr 1.0)"
    ]
    user_agent = random.choice(ua_list)

**2.增设延时**  
在爬虫的时候，降低爬虫频率，增设延时，多长时间爬取一次。不过爬虫的目的就是为了高效的抓取数据，不建议使用。

import time
    time.sleep(3)

**3.代理请求proxies**

#如果需要使用代理，可以通过为任意请求方法提供proxies参数来配置单个请求
    #根据协议类型，选择不同的代理
    '''
    proxies = {
      "https":"http://41.118.132.69:4433",
      "http":"http://41.118.132.69:4433"
    }
    r = requests.post("http://httpbin.org/post",proxies=proxies)
    print(r.text)
    '''
    #私密代理（特定格式）
    #如果代理需要使用HTTP Basic Auth，可以使用下面这种格式
    '''
    proxy = {"http": "mr_mao_hacker:sffqry9r@61.158.163.130:16816"}
    response = requests.get("http://www.baidu.com",proxies = proxy)
    print(response.text)
    '''