1. 执行流程

逻辑过程

Scrapy流程

执行过程

代码执行过程

2. 问提与解决

1. start_urls只能配置一个数组，如果我想动态配置爬取的源头怎么办？

重写 Spider 的 start_requests 函数，在里面设置请求

2. 如果我通过请求结果，发起新的请求怎么写？

直接在结果里面通过 yield发起新请求

3. 如果我通过请求结果发起新的请求，怎么处理新的响应结果？

在Spider里新增需要的处理的函数，配置 response 参数即可。

• yield scrapy.Request(next_page, callback=self.parse_new)
• def parse_new(self, response, **kwargs)

2. 如何把发起请求时候的参数传递到响应结果？

• 通过 Request 的 meta 参数，传输一个字典过去。
• 通过 response.meta 拿到你存入的值。

3. 如何给Spdier配置特点的中间件(middleware)、管道(pipelines)？

custom_settings

• ITEM_PIPELINES
• SPIDER_MIDDLEWARES
• DOWNLOADER_MIDDLEWARES

4. 对于一些异步加载的页面怎么处理？

   • 方案一：splash

     • docker 启动一个 Splash 代理服务：

       • docker run -it -p 8050:8050 --rm scrapinghub/splash

     • settings 配置：

        SPLASH_URL = 'http://host:port'
        DUPEFILTER_CLASS = 'scrapy_splash.SplashAwareDupeFilter'   
        HTTPCACHE_STORAGE = 'scrapy_splash.SplashAwareFSCacheStorage'
           SPIDER_MIDDLEWARES = {
          'scrapy_splash.SplashDeduplicateArgsMiddleware': 100,
        }  
        DOWNLOADER_MIDDLEWARES = {  
          'scrapy_splash.SplashCookiesMiddleware': 723,
          'scrapy_splash.SplashMiddleware': 725,
          'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware': 810
        }
       

     • python 导入依赖
       pip3 install scrapy-splash

     • Spider 中引入
       from scrapy_splash import SplashRequest

     • 请求替换

       • 从：Request(stock_url, self.parse, meta=params, dont_filter=True)
       • 到：SplashRequest(url, self.parse, meta=params, args={'wait': 0.5})

     • parse正常解析结果即可

   • 方案二：selenium

     • python 导入依赖
       pip3 install selenium

     • 配置 custom_settings：
       DOWNLOADER_MIDDLEWARES': { 'ht_msg.middlewares.SeleniumDownloadMiddleware': 500 }

     • 创建中间件

     from selenium.webdriver.chrome.options import Options 
     from selenium import webdriver from scrapy.http import HtmlResponse
     
     class SeleniumDownloadMiddleware(object): 
     
          def __init__(self): 
               chrome_options = Options() 
               chrome_options.add_argument(‘–headless’) 
               chrome_options.add_argument(‘–disable-gpu’)         
               chrome_options.add_argument(“window-size=1024,768”)                 
               chrome_options.add_argument(“–no-sandbox”) 
               self.driver = webdriver.Chrome(chrome_options=chrome_options)
     
         def process_request(self, request, spider):
             self.driver.get(request.url)
             time.sleep(12)
             source = self.driver.page_source
             url = self.driver.current_url
             return HtmlResponse(url=url, body=source, request=request, encoding="utf-8") ```
     

未完待续…..

参考的文件

• scrapy:
  • 文档
    • https://doc.scrapy.org/en/latest/topics/request-response.html#response-objects
  • 教程
    • https://geek-docs.com/scrapy/scrapy-tutorials/scrapy-css-grammar.html
    • https://www.jianshu.com/p/df9c0d1e9087
  • 多种方案：爬取动态JS
    • https://zhuanlan.zhihu.com/p/130867872
  • splash教程
    • https://splash.readthedocs.io/en/stable/
  • 配置可变的start_urls
    • https://blog.csdn.net/sirobot/article/details/105360486
  • splash
    • https://github.com/scrapy-plugins/scrapy-splash
  • xpath/css
    • https://zhuanlan.zhihu.com/p/65143300
  • 不同spider配置不同的pipline:
    • https://blog.csdn.net/peiwang245/article/details/100071316
  • response传递参数：
    • https://blog.csdn.net/killeri/article/details/80255500
  • spider的setting优先级
    • https://blog.csdn.net/he_ranly/article/details/85092065
  • 中间件的区别
    • https://www.jianshu.com/p/3a9a385b9483
• scrapy部署
  • APscheduler
    • https://apscheduler.readthedocs.io/en/latest/
  • subprocess
    • https://www.runoob.com/w3cnote/python3-subprocess.html
  • APscheduler+scarpy
    • https://apscheduler.readthedocs.io/en/latest/userguide.html
    • https://www.cnblogs.com/jdbc2nju/p/9563761.html
    • https://www.jianshu.com/p/c37c46de3168