xml数据处理--expat模块使用

# coding:utf-8
from login163 import *
from xml.parsers import expat
import MySQLdb
class mail163(Login163):
    '''
    get 'limit' unread mails at once,the data format is xml
    if 'subject' in xml data,then return the data,else return None
    '''
    def get_unread_mail(self,start,limit):
        postdata = {
            'var':''
        }
        postdata = urllib.urlencode(postdata)
        url = 'http://twebmail.mail.163.com/js5/s?sid='+self.sid+'&func=mbox:listMessages&deftabclick=t2&deftabclick=undefined&from=toolbar&type=unread&mboxentry=1'
        req = urllib2.Request(url=url,data=postdata,headers=self.headers)
        res = urllib2.urlopen(req).read()
        if 'subject' in res:
            return res
        else:
            return None
    '''
    xml data format,then return the data
    '''
    def format(self,xml_data):
        pattern = re.compile(r'|