【请初学者作为参考，不建议高手看这个浪费时间】
上一篇文章，我们抓取到了一大批代理ip，本篇文章介绍如何实现downloaderMiddleware，达到随即使用代理ip对目标网站进行抓取的。
抓取的目标网站是现在炙手可热的旅游网站 www.qunar.com, 目标信息是qunar的所有seo页面，及页面的seo相关信息。
qunar并没有一般网站具有的 robots.txt文件，所以无法利用列表进行抓取，但是，可以发现，qunar的seo页面主要部署在
http://www.qunar.com/routes/ 下，这个页面为入口文件，由此页面及此页面上所有带有routes的链接开始递归的抓取所有带有routes/字段的链接即可。
开始吧
目标信息为目标站点的seo信息，所以为head中的meta和description字段。
1 # Define here the models for your scraped items 2 # 3 # See documentation in: 4 # http://doc.scrapy.org/topics/items.html 5 6 from scrapy.item import Item, Field 7 8 class SitemapItem(Item): 9 # define the fields for your item here like: 10 # name = Field() 11 url = Field() 12 keywords = Field() 13 description = Field()
因为要使用代理ip，所以需要实现自己的downloadermiddlerware，主要功能是从代理ip文件中随即选取一个ip端口作为代理服务，代码如下
1 import random 2 3 class ProxyMiddleware(object): 4 def process_request(self, request, spider): 5 fd = open('/home/xxx/services_runenv/crawlers/sitemap/sitemap/data/proxy_list.txt','r') 6 data = fd.readlines() 7 fd.close() 8 length = len(data) 9 index = random.randint(0, length -1) 10 item = data[index] 11 arr = item.split(',') 12 request.meta['proxy'] = 'http://%s:%s' % (arr[0],arr[1])
最重要的还是爬虫，主要功能是提取页面所有的链接，把满足条件的url实例成Request对象并yield， 同时提取页面的keywords，description信息，以item的形式yield，代码如下:
1 from scrapy.selector import HtmlXPathSelector 2 from sitemap.items import SitemapItem 3 4 import urllib 5 import simplejson 6 import exceptions 7 import pickle 8 9 class SitemapSpider(CrawlSpider): 10 name = 'sitemap_spider' 11 allowed_domains = ['qunar.com'] 12 start_urls = ['http://www.qunar.com/routes/'] 13 14 rules = ( 15 #Rule(SgmlLinkExtractor(allow=(r'http://www.qunar.com/routes/.*')), callback='parse'), 16 #Rule(SgmlLinkExtractor(allow=('http:.*/routes/.*')), callback='parse'), 17 ) 18 19 def parse(self, response): 20 item = SitemapItem() 21 x = HtmlXPathSelector(response) 22 raw_urls = x.select("//a/@href").extract() 23 urls = [] 24 for url in raw_urls: 25 if 'routes' in url: 26 if 'http' not in url: 27 url = 'http://www.qunar.com' + url 28 urls.append(url) 29 30 for url in urls: 31 yield Request(url) 32 33 item['url'] = response.url.encode('UTF-8') 34 arr_keywords = x.select("//meta[@name='keywords']/@content").extract() 35 item['keywords'] = arr_keywords[0].encode('UTF-8') 36 arr_description = x.select("//meta[@name='description']/@content").extract() 37 item['description'] = arr_description[0].encode('UTF-8') 38 39 yield item
pipe文件比较简单，只是把抓取到的数据存储起来，代码如下
1 # Define your item pipelines here 2 # 3 # Don't forget to add your pipeline to the ITEM_PIPELINES setting 4 # See: http://doc.scrapy.org/topics/item-pipeline.html 5 6 class SitemapPipeline(object): 7 def process_item(self, item, spider): 8 data_path = '/home/xxx/services_runenv/crawlers/sitemap/sitemap/data/output/sitemap_data.txt' 9 fd = open(data_path, 'a') 10 line = str(item['url']) + '#$#' + str(item['keywords']) + '#$#' + str(item['description']) + '\n' 11 fd.write(line) 12 fd.close 13 return item
最后附上的是setting.py文件
# Scrapy settings for sitemap project # # For simplicity, this file contains only the most important settings by # default. All the other settings are documented here: # # http://doc.scrapy.org/topics/settings.html # BOT_NAME = 'sitemap hello,world~!' BOT_VERSION = '1.0' SPIDER_MODULES = ['sitemap.spiders'] NEWSPIDER_MODULE = 'sitemap.spiders' USER_AGENT = '%s/%s' % (BOT_NAME, BOT_VERSION) DOWNLOAD_DELAY = 0 ITEM_PIPELINES = [ 'sitemap.pipelines.SitemapPipeline' ] DOWNLOADER_MIDDLEWARES = { 'scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware': 110, 'sitemap.middlewares.ProxyMiddleware': 100, } CONCURRENT_ITEMS = 128 CONCURRENT_REQUEST = 64 CONCURRENT_REQUEST_PER_DOMAIN = 64 LOG_ENABLED = True LOG_ENCODING = 'utf-8' LOG_FILE = '/home/xxx/services_runenv/crawlers/sitemap/sitemap/log/sitemap.log' LOG_LEVEL = 'DEBUG' LOG_STDOUT = False
对scrapy的介绍将告一段落，更复杂的应用还没有接触过，想等看完redis的源码，再来研究下scrapy的源码~~ 希望通过分享能给正在入门scrapy的童鞋带来帮助~
喜欢一起简单，实用的东西，拒绝复杂花哨，我不是GEEK.
