Python-crawler-citeulike

之前装过beautifulsoup,这次要装lxml，用easy_install装：到python/scripts目录下，运行easy_install lxml，自动安装

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之前直接用urlopen(url)，拒绝访问，403forbidden

模仿真实上网，添加cookie （转自http://www.yihaomen.com/article/python/210.htm）

import re
import random
import socket
import urllib2
import cookielib
from bs4 import BeautifulSoup
import lxml

ERROR = {
        '0':'Can not open the url,checck you net',
        '1':'Creat download dir error',
        '2':'The image links is empty',
        '3':'Download faild',
        '4':'Build soup error,the html is empty',
        '5':'Can not save the image to your disk',
    }

class BrowserBase(object): 

    def __init__(self):
        socket.setdefaulttimeout(20)
        
    def speak(self,name,content):
        print '[%s]%s' %(name,content)

    def openurl(self,url):
        """
        打开网页
        """
        cookie_support= urllib2.HTTPCookieProcessor(cookielib.CookieJar())
        self.opener = urllib2.build_opener(cookie_support,urllib2.HTTPHandler)
        urllib2.install_opener(self.opener)
        user_agents = [
                    'Mozilla/5.0 (Windows; U; Windows NT 5.1; it; rv:1.8.1.11) Gecko/20071127 Firefox/2.0.0.11',
                    'Opera/9.25 (Windows NT 5.1; U; en)',
                    'Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)',
                    'Mozilla/5.0 (compatible; Konqueror/3.5; Linux) KHTML/3.5.5 (like Gecko) (Kubuntu)',
                    'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.12) Gecko/20070731 Ubuntu/dapper-security Firefox/1.5.0.12',
                    'Lynx/2.8.5rel.1 libwww-FM/2.14 SSL-MM/1.4.1 GNUTLS/1.2.9',
                    "Mozilla/5.0 (X11; Linux i686) AppleWebKit/535.7 (KHTML, like Gecko) Ubuntu/11.04 Chromium/16.0.912.77 Chrome/16.0.912.77 Safari/535.7",
                    "Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:10.0) Gecko/20100101 Firefox/10.0 ",

                    ] 
       
        agent = random.choice(user_agents)
        self.opener.addheaders = [("User-agent",agent),("Accept","*/*"),('Referer','http://www.google.com')]
        try:
            res = self.opener.open(url)
         #   print res.read()
        except Exception,e:
            self.speak(str(e)+url)
            raise Exception
        else:
            return res

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用beautifulsoup解析html文件（教程参考：http://beautifulsoup.readthedocs.org/zh_CN/latest/#）

soup = BeautifulSoup(res, "lxml) 生成beautifulsoup对象，是一棵由html里的tag作节点的树对象。

soup = BeautifulSoup(res,"lxml")
tag = soup.find(id ="showtexform") #body.form( id ="showtexform")
return tag.contents[1].contents[1]['value']

beautifulsoup的搜索方法：find()，find_all()：

   1. 字符串：查找与字符串完整匹配的内容，soup.find_all('b')；找b标签

   2. 正则表达式：通过正则表达式的 match() 来匹配，soup.find_all(re.compile('^b'))；找b打头的标签

   3. 列表

   ......

tag的属性的操作方法与字典相同: tag['value']

tag的 .contents 属性可以将tag的子节点以列表的方式输出