Python多线程抓取Google搜索链接网页
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：
python;toolbar:false;">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=8
pages=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()
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