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scrapy 中间件

程序员文章站 2022-05-09 13:02:14
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下载中间件的应用

  • scrapy中间件有:-爬虫中间件,下载中间件
  • 下载中间件应用较多
  • 下载中间件:
    • 作用:批量拦截请求和响应
    • 拦截请求:
    • UA伪装:将所有的请求尽可能多的设定成不同的请求载体身份标识
      • request.headers['User-Agent'] = 'xxx'
    • 代理操作:request.meta['proxy'] = 'http://ip:port'
    • 拦截响应:篡改响应数据或者直接替换响应对象

1 拦截请求中间件

  • 作用:
    • UA伪装:将所有的请求尽可能多的设定成不同的请求载体身份标识
      • request.headers['User-Agent'] = 'xxx'
    • 代理操作:request.meta['proxy'] = 'http://ip:port'
  • 爬取4567视频网示例:

    • spider.py文件
    import scrapy
    from moviespider.items import MoviespiderItem
    
    class MovieSpiderSpider(scrapy.Spider):
        name = 'movie_spider'
        # allowed_domains = ['https://www.4567tv.tv/index.php/vod/show/class/动作/id/1.html']
        start_urls = ['https://www.4567tv.tv/index.php/vod/show/class/动作/id/1.html']
        url = 'https://www.4567tv.tv/index.php/vod/show/class/动作/id/1/page/%d.html'
        pageNum = 1
    
        def parse(self, response):
            li_list = response.xpath('/html/body/div[1]/div/div/div/div[2]/ul/li')
            for li in li_list:
                title = li.xpath('./div[1]/a/@title').extract_first()
                detail_url = 'https://www.4567tv.tv' + li.xpath('./div[1]/a/@href').extract_first()
                item = MoviespiderItem()
                item['title'] = title
                # meta参数是一个字典,该字典就可以传递给callback指定的回调函数
                yield scrapy.Request(detail_url, callback=self.parse_detail, meta={"item": item})
    
        def parse_detail(self, response):
            # 接收meta:response.meta
            item = response.meta['item']
            desc = response.xpath('/html/body/div[1]/div/div/div/div[2]/p[5]/span[2]/text()').extract_first()
            item["desc"] = desc
            yield item
    • items.py

      • 创建title和desc的属性
    • pipelines.py文件

      • 存储
    • middleware.py

      • downloadmiddleware文件
      from scrapy import signals
      import random
      
      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",
      ]  # 常见浏览器user_agent
      
      PROXY_http = [
          '153.180.102.104:80',
      ]
      PROXY_https = [
          '120.83.49.90:9000',
      ]
      
      
      class MoviespiderDownloaderMiddleware(object):
      
          # 拦截正常的请求,参数request就是拦截到的请求对象
          def process_request(self, request, spider):
              print('i am process_request()')
              # 实现:将拦截到的请求尽可能多的设定成不同的请求载体身份标识
              request.headers['User-Agent'] = random.choice(user_agent_list)
              # 代理操作
              if request.url.split(':')[0] == 'http':
                  request.meta['proxy'] = 'http://' + random.choice(PROXY_http)  # http://ip:port
              else:
                  request.meta['proxy'] = 'https://' + random.choice(PROXY_https)  # http://ip:port
      
              return
      
          # 拦截响应:参数response就是拦截到的响应
          def process_response(self, request, response, spider):
              print('i am process_response()')
              return response
      
          def process_exception(self, request, exception, spider):
              print('i am process_exception()')
              # 拦截到异常的请求然后对其进行修正,然后重新进行请求发送
              # 代理操作
              if request.url.split(':')[0] == 'http':
                  request.meta['proxy'] = 'http://' + random.choice(PROXY_http)  # http://ip:port
              else:
                  request.meta['proxy'] = 'https://' + random.choice(PROXY_https)  # http://ip:port
      
              return request  # 将修正之后的请求进行重新发送
      
  • 常用浏览器user_agent

    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"
    ]

2 拦截响应中间件

  • 作用:拦截响应可以篡改响应数据或者直接替换响应对象

  • selenium在scrapy中的应用:

    • 实例化浏览器对象:写在爬虫类的构造方法中
    • 关闭浏览器:爬虫类中的closed(self,spider)关闭浏览器
    • 在中间件中执行浏览器自动化的操作
  • 示例:

    • 需求; 爬取网易新闻的国内,国际,军事,航空,无人机这五个板块下对应的新闻标题和内容(数据是动态加载的)

    • spider.py文件

      # -*- coding: utf-8 -*-
      import scrapy
      from selenium import webdriver
      from wangyinews.item import WangyinewsItem
      
      class NewsSpider(scrapy.Spider):
          name = 'news'
          # allowed_domains = ['www.wangyi.com']
          start_urls = ['https://news.163.com']
          five_model_urls = []
          bro = webdriver.Chrome(executable_path=r'D:\教学视频\python 爬虫\tools\chromedriver.exe')
      
          # 用来解析五个板块对应的url,然后对其进行手动请求发送
          def parse(self, response):
              model_index = [3, 4, 6, 7, 8]
              li_list = response.xpath('//*[@id="index2016_wrap"]/div[1]/div[2]/div[2]/div[2]/div[2]/div/ul/li')
              for index in model_index:
                  li = li_list[index]
                  # 获取了五个板块对应的url
                  model_url = li.xpath('./a/@href').extract_first()
                  self.five_model_urls.append(model_url)
                  # 对每一个板块的url进行手动i请求发送
                  yield scrapy.Request(model_url, callback=self.parse_model)
      
          # 解析每一个板块页面中的新闻标题和新闻详情页的url
          # 问题:response(不满足需求的response)中并没有包含每一个板块中动态加载出的新闻数据
          def parse_model(self, response):
              div_list = response.xpath('/html/body/div[1]/div[3]/div[4]/div[1]/div/div/ul/li/div/div')
              for div in div_list:
                  title = div.xpath('./div/div[1]/h3/a/text()').extract_first()
                  detail_url = div.xpath('./div/div[1]/h3/a/@href').extract_first()
                  item = WangyinewsItem()
                  item['title'] = title
                  # 对详情页发起请求解析出新闻内容
                  yield scrapy.Request(detail_url, callback=self.parse_new_content, meta={'item': item})
      
          # 获取内容详情
          def parse_new_content(self, response):
              item = response.meta["item"]
              content = response.xpath('//*[@id="endText"]//text()').extract()
              item["content"] = content
              yield item
      
          # 最后执行,关闭bro
          def close(self, spider):
              self.bro.quit()
      
    • items.py

      • 创建title和desc的属性
    • pipelines.py文件

      • 存储
    • middleware.py文件:

      # -*- coding: utf-8 -*-
      
      # Define here the models for your spider middleware
      #
      # See documentation in:
      # https://docs.scrapy.org/en/latest/topics/spider-middleware.html
      from time import sleep
      
      from scrapy import signals
      from scrapy.http import HtmlResponse
      
      
      class WangyinewsDownloaderMiddleware(object):
      
          def process_request(self, request, spider):
              return None
      
          def process_response(self, request, response, spider):
              # spider就是爬虫文件中爬虫类实例化的对象
              # 进行所有响应对象的拦截
              # 1.将所有的响应中那五个不满足需求的响应对象找出
              # 1.每一个响应对象对应唯一一个请求对象
              # 2.如果我们可以定位到五个响应对应的请求对象后,就可以通过该i请求对象定位到指定的响应对象
              # 3.可以通过五个板块的url定位请求对象
              # 总结: url==》request==》response
              # 2.将找出的五个不满足需求的响应对象进行修正(替换)
              # spider.five_model_urls:五个板块对应的url
              bro = spider.bro
              if request.url in spider.five_model_urls:
                  bro.get(request.url)
                  sleep(1)
                  page_text = bro.page_source  # 包含了动态加载的新闻数据
                  # 如果if条件程利则该response就是五个板块对应的响应对象
                  new_responde = HtmlResponse(url=request.url, body=page_text, encoding="utf-8", request=request)
                  return new_responde
              return response
      
          def process_exception(self, request, exception, spider):
              pass