• 動態設定user agent
• 禁用cookies
• 設定延遲下載
• 使用IP地址池（ Tor project 、VPN和代理IP）

由於Google cache受國內網路的影響，你懂得；Crawlera的分散式下載，我們可以在下次用一篇專門的文章進行講解。所以本文主要從動態隨機設定user agent、禁用cookies、設定延遲下載和使用代理IP這幾個方式。好了，入正題：

1、建立middlewares.py

scrapy代理IP、user agent的切換都是通過DOWNLOADER_MIDDLEWARES進行控制，下面我們建立middlewares.py檔案。

[root@bogon cnblogs]#
 
 vi cnblogs/middlewares.py
import random
import base64
from settings import PROXIES
class RandomUserAgent(object):"""Randomly rotate user agents based on a list of predefined ones"""
def __init__(self, agents):
self.agents = agents
@classmethod
def from_crawler(cls, crawler):return cls(crawler.settings.getlist('
 
USER_AGENTS'))
def process_request(self, request, spider):#print "**************************" + random.choice(self.agents)
request.headers.setdefault('User-Agent', random.choice(self.agents))
class ProxyMiddleware(object):def process_request(self, request, spider):
proxy = random.choice(PROXIES)
if proxy['
 
user_pass'] is not None:
request.meta['proxy'] = "http://%s" % proxy['ip_port']
encoded_user_pass = base64.encodestring(proxy['user_pass'])
request.headers['Proxy-Authorization'] = 'Basic ' + encoded_user_pass
print "**************ProxyMiddleware have pass************" + proxy['ip_port']
else:
print "**************ProxyMiddleware no pass************" + proxy['ip_port']
request.meta['proxy'] = "http://%s" % proxy['ip_port']

類RandomUserAgent主要用來動態獲取user agent，user agent列表USER_AGENTS在settings.py中進行配置。

類ProxyMiddleware用來切換代理，proxy列表PROXIES也是在settings.py中進行配置 。

2、修改settings.py配置USER_AGENTS和PROXIES

a)：新增USER_AGENTS

USER_AGENTS = [
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; AcooBrowser; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
"Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Acoo Browser; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506)",
"Mozilla/4.0 (compatible; MSIE 7.0; AOL 9.5; AOLBuild 4337.35; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
"Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)",
"Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 2.0.50727; Media Center PC 6.0)",
"Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 1.0.3705; .NET CLR 1.1.4322)",
"Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 3.0.04506.30)",
"Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN) AppleWebKit/523.15 (KHTML, like Gecko, Safari/419.3) Arora/0.3 (Change: 287 c9dfb30)",
"Mozilla/5.0 (X11; U; Linux; en-US) AppleWebKit/527+ (KHTML, like Gecko, Safari/419.3) Arora/0.6",
"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2pre) Gecko/20070215 K-Ninja/2.1.1",
"Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9) Gecko/20080705 Firefox/3.0 Kapiko/3.0",
"Mozilla/5.0 (X11; Linux i686; U;) Gecko/20070322 Kazehakase/0.4.5",
"Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.8) Gecko Fedora/1.9.0.8-1.fc10 Kazehakase/0.5.6",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11",
"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like Gecko) Chrome/19.0.1036.7 Safari/535.20",
"Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; fr) Presto/2.9.168 Version/11.52",
]

b)：新增代理IP設定PROXIES

PROXIES = [
{'ip_port': '111.11.228.75:80', 'user_pass': ''},
{'ip_port': '120.198.243.22:80', 'user_pass': ''},
{'ip_port': '111.8.60.9:8123', 'user_pass': ''},
{'ip_port': '101.71.27.120:80', 'user_pass': ''},
{'ip_port': '122.96.59.104:80', 'user_pass': ''},
{'ip_port': '122.224.249.122:8088', 'user_pass': ''},
]

代理IP可以網上搜索一下，上面的代理IP獲取自：http://www.xici.net.co/。

c)：禁用cookies

COOKIES_ENABLED=False

d)：設定下載延遲

DOWNLOAD_DELAY=3

儲存settings.py