用Scrapy抓取豆瓣小组数据（二）

接着上篇博客《用Scrapy抓取豆瓣小组数据（一)》/article/3497804.html

在scrapy中怎么让Spider自动去抓取豆瓣小组页面

1，引入Scrapy中的另一个预定义的蜘蛛CrawlSpider

from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor

2， 基于CrawSpider定义一个新的类GroupSpider，并添加相应的爬行规则。

class GroupSpider(CrawlSpider):
name = "Group"
allowed_domains = ["douban.com"]
start_urls = [
"http://www.douban.com/group/explore?tag=%E8%B4%AD%E7%89%A9",
"http://www.douban.com/group/explore?tag=%E7%94%9F%E6%B4%BB",
"http://www.douban.com/group/explore?tag=%E7%A4%BE%E4%BC%9A",
"http://www.douban.com/group/explore?tag=%E8%89%BA%E6%9C%AF",
"http://www.douban.com/group/explore?tag=%E5%AD%A6%E6%9C%AF",
"http://www.douban.com/group/explore?tag=%E6%83%85%E6%84%9F",
"http://www.douban.com/group/explore?tag=%E9%97%B2%E8%81%8A",
"http://www.douban.com/group/explore?tag=%E5%85%B4%E8%B6%A3"
]

rules = [
Rule(SgmlLinkExtractor(allow=('/group/[^/]+/$', )), callback='parse_group_home_page', process_request='add_cookie'),
Rule(SgmlLinkExtractor(allow=('/group/explore\?tag', )), follow=True, process_request='add_cookie'),
]

start_urls预定义了豆瓣有所小组分类页面，蜘蛛会从这些页面出发去找小组。
rules定义是CrawlSpider中最重要的一环，可以理解为：当蜘蛛看到某种类型的网页，如何去进行处理。

例如，如下规则会处理URL以/group/XXXX/为后缀的网页，调用parse_group_home_page为处理函数，并且会在request发送前调用add_cookie来附加cookie信息。

Rule(SgmlLinkExtractor(allow=('/group/[^/]+/$', )), callback='parse_group_home_page', process_request='add_cookie'),

又如，如下规则会抓取网页内容，并自动抓取网页中链接供下一步抓取，但不会处理网页的其他内容。

Rule(SgmlLinkExtractor(allow=('/group/explore\?tag', )), follow=True, process_request='add_cookie'),

如何添加Cookie

定义如下函数，并如前面所讲在Rule定义里添加process_request=add_cookie。

def add_cookie(self, request):
request.replace(cookies=[
{'name': 'COOKIE_NAME','value': 'VALUE','domain': '.douban.com','path': '/'},
]);
return request;

一般网站在client端都用cookie来保存用户的session信息，添加cookie信息就可以模拟登陆用户来抓取数据。

如何防止蜘蛛被网站Ban掉

首先可以尝试添加登陆用户的cookie去抓取网页，即使你抓取的是公开网页，添加cookie有可能会防止蜘蛛在应用程序层被禁。这个我没有实际验证过，但肯定没有坏处。

其次，即使你是授权用户，如果你的访问过于频繁，你的IP会可能被ban，所以一般你需要让蜘蛛在访问网址中间休息1~2秒。

还有就是配置User Agent，尽量轮换使用不同的UserAgent去抓取网页

在Scrapy项目的settings.py钟，添加如下设置：

DOWNLOAD_DELAY = 2
RANDOMIZE_DOWNLOAD_DELAY = True
USER_AGENT = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_3) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.54 Safari/536.5'
COOKIES_ENABLED = True

================

到此位置，抓取豆瓣小组页面的蜘蛛就完成了。接下来，可以按照这种模式定义抓取小组讨论页面数据的Spider，然后就放手让蜘蛛去爬行吧！Have Fun！

from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor
from scrapy.selector import HtmlXPathSelector
from scrapy.item import Item
from douban.items import DoubanItem
import re

class GroupSpider(CrawlSpider):
name = "Group"
allowed_domains = ["douban.com"]
start_urls = [
"http://www.douban.com/group/explore?tag=%E8%B4%AD%E7%89%A9",
"http://www.douban.com/group/explore?tag=%E7%94%9F%E6%B4%BB",
"http://www.douban.com/group/explore?tag=%E7%A4%BE%E4%BC%9A",
"http://www.douban.com/group/explore?tag=%E8%89%BA%E6%9C%AF",
"http://www.douban.com/group/explore?tag=%E5%AD%A6%E6%9C%AF",
"http://www.douban.com/group/explore?tag=%E6%83%85%E6%84%9F",
"http://www.douban.com/group/explore?tag=%E9%97%B2%E8%81%8A",
"http://www.douban.com/group/explore?tag=%E5%85%B4%E8%B6%A3"
]

rules = [
Rule(SgmlLinkExtractor(allow=('/group/[^/]+/$', )), callback='parse_group_home_page', process_request='add_cookie'),
#   Rule(SgmlLinkExtractor(allow=('/group/[^/]+/discussion\?start\=(\d{1,4})$', )), callback='parse_group_topic_list', process_request='add_cookie'),
Rule(SgmlLinkExtractor(allow=('/group/explore\?tag', )), follow=True, process_request='add_cookie'),
]

def __get_id_from_group_url(self, url):
m =  re.search("^http://www.douban.com/group/([^/]+)/$", url)
if(m):
return m.group(1)
else:
return 0

def add_cookie(self, request):
request.replace(cookies=[

]);
return request;

def parse_group_topic_list(self, response):
self.log("Fetch group topic list page: %s" % response.url)
pass

def parse_group_home_page(self, response):

self.log("Fetch group home page: %s" % response.url)

hxs = HtmlXPathSelector(response)
item = DoubanItem()

#get group name
item['groupName'] = hxs.select('//h1/text()').re("^\s+(.*)\s+$")[0]

#get group id
item['groupURL'] = response.url
groupid = self.__get_id_from_group_url(response.url)

#get group members number
members_url = "http://www.douban.com/group/%s/members" % groupid
members_text = hxs.select('//a[contains(@href, "%s")]/text()' % members_url).re("\((\d+)\)")
item['totalNumber'] = members_text[0]

#get relative groups
item['RelativeGroups'] = []
groups = hxs.select('//div[contains(@class, "group-list-item")]')
for group in groups:
url = group.select('div[contains(@class, "title")]/a/@href').extract()[0]
item['RelativeGroups'].append(url)
#item['RelativeGroups'] = ','.join(relative_groups)
return item