实战中我们的爬虫很容易被对方ban,如何反ban是一门很深的功课。我们来学学最简单的。
通常情况下,最容易想到的有两个,一个是用户代理(user-agent),还有一个就是ip代理(proxy)。下面我们就要学一个新的组件middlewares。
middlewares组件是一组中间件,主要是处理爬虫系统的输入输出数据,包括request和response数据。
首先需要自定义一个middleware组件,随便起个名字SampleUserAgentMiddleware,用户代理的middleware继承scrapy.contrib.downloadermiddleware.useragent.UserAgentMiddleware,然后实现他的process_request方法。具体实现是这样的,我们定义一个用户代理的列表,也可以动态生成,简单起见,我们写个固定的列表,然后随机选取一个,之后把它塞到request请求的User-Agent参数中即可。
class SampleUserAgentMiddleware(useragent.UserAgentMiddleware):
#代理
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",
]
def __init__(self, user_agent=''):
self.user_agent = user_agent
def process_request(self, request, spider):
#随机选择一个user-agent
agent = random.choice(self.agents)
request.headers.setdefault('User-Agent', agent)
接下来我们再来实现一个ip代理,也是很简单的,我们定义一个middleware组件,然后实现process_request方法就可以了,这里我们演示采用fiddler代理。
class ProxyMiddleware(object):
def process_request(self, request, spider):
proxy = 'http://localhost:8888'
request.meta['proxy'] = proxy
要想middleware工作,我们还需要在setting中开启配置,
DOWNLOADER_MIDDLEWARES = {
# 'sample.middlewares.MyCustomDownloaderMiddleware': 543,2019-09-04 13:57:43 星期三
'sample.middlewares.SampleUserAgentMiddleware': 100,
'sample.middlewares.ProxyMiddleware': 200,
}
我们来验证下
我们可以看到代理成功获取。
总结
总的来说,通过scrapy来实现爬虫还是很简单的。因其高度封装特性,以及模块化的设计,极大地便利了开发者。但是想要用做好爬虫还有很远的路要走,比如反爬,分布式爬虫的设计等等。