python自定义解析简单xml格式文件的方法

#!/usr/bin/env python
#encoding: utf-8
import re
class xmlparse:
  def __init__(self, xmlstr):
    self.xmlstr = xmlstr
    self.xmldom = self.__convet2utf8()
    self.xmlnodelist = []
    self.xpath = ''
  def __convet2utf8(self):
    headstr = self.__get_head()
    xmldomstr = self.xmlstr.replace(headstr, '')
    if 'gbk' in headstr: 
      xmldomstr = xmldomstr.decode('gbk').encode('utf-8')
    elif 'gb2312' in headstr:
      xmldomstr = self.xmlstr.decode('gb2312').encode('utf-8')
    return xmldomstr
  def __get_head(self):
    headpat = r'<\?xml.*\?>'
    headpatobj = re.compile(headpat)
    headregobj = headpatobj.match(self.xmlstr)
    if headregobj:
      headstr = headregobj.group()
      return headstr
    else:
      return ''
  def parse(self, xpath):
    self.xpath = xpath
    xpatlist = []
    xpatharr = self.xpath.split('/')
    for xnode in xpatharr:
      if xnode:
        spcindex = xnode.find('[')
        if spcindex > -1:
          index = int(xnode[spcindex+1:-1])
          xnode = xnode[:spcindex]
        else:
          index = 0;
        temppat = ('<%s>(.*?)</%s>' % (xnode, xnode),index)
        xpatlist.append(temppat)
    xmlnodestr = self.xmldom
    for xpat,index in xpatlist:
      xmlnodelist = re.findall(xpat,xmlnodestr)
      xmlnodestr = xmlnodelist[index]
      if xmlnodestr.startswith(r'<![CDATA['):
        xmlnodestr = xmlnodestr.replace(r'<![CDATA[','')[:-3]
    self.xmlnodelist = xmlnodelist
    return xmlnodestr
if '__main__' == __name__:
  xmlstr = '<?xml version="1.0" encoding="utf-8" standalone="yes" ?><resultObject><a><product_id>aaaaa</product_id><product_name><![CDATA[bbbbb]]></a><b><product_id>bbbbb</product_id><product_name><![CDATA[bbbbb]]></b></product_name></resultObject>'
  xpath1 = '/product_id'
  xpath2 = '/product_id[1]'
  xpath3 = '/a/product_id'
  xp = xmlparse(xmlstr)
  print 'xmlstr:',xp.xmlstr
  print 'xmldom:',xp.xmldom
  print '------------------------------'
  getstr = xp.parse(xpath1)
  print 'xpath:',xp.xpath
  print 'get list:',xp.xmlnodelist
  print 'get string:', getstr
  print '------------------------------'
  getstr = xp.parse(xpath2)
  print 'xpath:',xp.xpath
  print 'get list:',xp.xmlnodelist
  print 'get string:', getstr
  print '------------------------------'
  getstr = xp.parse(xpath3)
  print 'xpath:',xp.xpath
  print 'get list:',xp.xmlnodelist
  print 'get string:', getstr

xmlstr: <?xml version="1.0" encoding="utf-8" standalone="yes" ?><resultObject><a><product_id>aaaaa</product_id><product_name><![CDATA[bbbbb]]></a><b><product_id>bbbbb</product_id><product_name><![CDATA[bbbbb]]></b></product_name></resultObject>
xmldom: <resultObject><a><product_id>aaaaa</product_id><product_name><![CDATA[bbbbb]]></a><b><product_id>bbbbb</product_id><product_name><![CDATA[bbbbb]]></b></product_name></resultObject>
------------------------------
xpath: /product_id
get list: ['aaaaa', 'bbbbb']
get string: aaaaa
------------------------------
xpath: /product_id[1] 
get list: ['aaaaa', 'bbbbb']
get string: bbbbb
------------------------------
xpath: /a/product_id
get list: ['aaaaa']
get string: aaaaa