scrapy爬虫防止被禁止 User Agent切换

http://doc.scrapy.org/en/1.0/topics/practices.html#bans

1. User Agent轮换

2. 禁Cookie

3. 设置大于2s的DOWNLOAD_DELAY

4. 使用Google Cache (不懂)

5. 使用轮换IP(还不会)

6. 使用分布式下载器（不知道scrapy-redis算不算）

User Agent轮换例子

1）新建一个middlewares.py文件，内容如下，文件放在与items.py, settings.py所在的文件夹下。

#!/usr/bin/python
#-*-coding:utf-8-*-

import random
from scrapy.downloadermiddlewares.useragent import UserAgentMiddleware

class RotateUserAgentMiddleware(UserAgentMiddleware):
def __init__(self, user_agent=''):
self.user_agent = user_agent

def process_request(self, request, spider):
ua = random.choice(self.user_agent_list)
if ua:
print ua, '-----------------yyyyyyyyyyyyyyyyyyyyyyyyy'
request.headers.setdefault('User-Agent', ua)

#the default user_agent_list composes chrome,I E,firefox,Mozilla,opera,netscape
#for more user agent strings,you can find it in http://www.useragentstring.com/pages/useragentstring.php 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） 然后在settings.py中按如下设置

DOWNLOADER_MIDDLEWARES = {
'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware':None,
'example.middlewares.RotateUserAgentMiddleware':400,
}

运行爬虫scrapy crawl spider1 -L WARNING 不打印Debug信息，可以清楚得看到print出来的User Agent不同。