1）urllib2+BeautifulSoup抓取Goolge搜索链接
近期，参与的项目需要对Google搜索结果进行处理，之前学习了Python处理网页相关的工具。实际应用中，使用了urllib2和beautifulsoup来进行网页的抓取，但是在抓取google搜索结果的时候，发现如果是直接对google搜索结果页面的源代码进行处理，会得到很多“脏”链接。
看下图为搜索“titanic james”的结果：
图中红色标记的是不需要的，蓝色标记的是需要抓取处理的。
这种“脏链接”当然可以通过规则过滤的方法来过滤掉，但是这样程序的复杂度就高了。正当自己愁眉苦脸的正在写过滤规则时。同学提醒说google应该提供相关的api，才恍然大明白。
（2）Google Web Search API+多线程
文档中给出使用Python进行搜索的例子：
import simplejson # The request also includes the userip parameter which provides the end # user's IP address. Doing so will help distinguish this legitimate # server-side traffic from traffic which doesn't come from an end-user. url = ('https://ajax.googleapis.com/ajax/services/search/web' '?v=1.0&q=Paris%20Hilton&userip=USERS-IP-ADDRESS') request = urllib2.Request( url, None, {'Referer': /* Enter the URL of your site here */}) response = urllib2.urlopen(request) # Process the JSON string. results = simplejson.load(response) # now have some fun with the results... import simplejson # The request also includes the userip parameter which provides the end# user's IP address. Doing so will help distinguish this legitimate# server-side traffic from traffic which doesn't come from an end-user.url = ('https://ajax.googleapis.com/ajax/services/search/web' '?v=1.0&q=Paris%20Hilton&userip=USERS-IP-ADDRESS') request = urllib2.Request( url, None, {'Referer': /* Enter the URL of your site here */})response = urllib2.urlopen(request) # Process the JSON string.results = simplejson.load(response)# now have some fun with the results..实际应用中可能需要抓取google的很多网页，所以还需要使用多线程来分担抓取任务。使用google web search api的参考详细介绍，请看此处（这里介绍了Standard URL Arguments）。另外要特别注意，url中参数rsz必须是8（包括8）以下的值，若大于8，会报错的！
（3）代码实现
代码实现还存在问题，但是能够运行，鲁棒性差，还需要进行改进，希望各路大神指出错误（初学Python），不胜感激。
#-*-coding:utf-8-*- import urllib2,urllib import simplejson import os, time,threading import common, html_filter #input the keywords keywords = raw_input('Enter the keywords: ') #define rnum_perpage, pages rnum_perpage=8pages=8 #定义线程函数 def thread_scratch(url, rnum_perpage, page): url_set = [] try: request = urllib2.Request(url, None, {'Referer': 'http://www.sina.com'}) response = urllib2.urlopen(request) # Process the JSON string. results = simplejson.load(response) info = results['responseData']['results'] except Exception,e: print 'error occured' print e else: for minfo in info: url_set.append(minfo['url']) print minfo['url'] #处理链接 i = 0 for u in url_set: try: request_url = urllib2.Request(u, None, {'Referer': 'http://www.sina.com'}) request_url.add_header( 'User-agent', 'CSC' ) response_data = urllib2.urlopen(request_url).read() #过滤文件 #content_data = html_filter.filter_tags(response_data) #写入文件 filenum = i+page filename = dir_name+'/related_html_'+str(filenum) print ' write start: related_html_'+str(filenum) f = open(filename, 'w+', -1) f.write(response_data) #print content_data f.close() print ' write down: related_html_'+str(filenum) except Exception, e: print 'error occured 2' print e i = i+1 return #创建文件夹 dir_name = 'related_html_'+urllib.quote(keywords) if os.path.exists(dir_name): print 'exists file' common.delete_dir_or_file(dir_name) os.makedirs(dir_name) #抓取网页 print 'start to scratch web pages:'for x in range(pages): print "page:%s"%(x+1) page = x * rnum_perpage url = ('https://ajax.googleapis.com/ajax/services/search/web' '?v=1.0&q=%s&rsz=%s&start=%s') % (urllib.quote(keywords), rnum_perpage,page) print url t = threading.Thread(target=thread_scratch, args=(url,rnum_perpage, page)) t.start() #主线程等待子线程抓取完 main_thread = threading.currentThread() for t in threading.enumerate(): if t is main_thread: continue t.join() 