python - 如何使用 python minidom 从 XML 中提取数据

Question

给定这个 xml 文件，我想从中提取数据。但是，我无法从 <LandmarkPointListXml> 中提取数据。从此。

XML 文件:

  <?xml version="1.0" encoding="utf-8"?>
  <Map xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <MapName>er</MapName>
  <MapURL>er.gif</MapURL>
  <Name>er</Name>
  <URL>er.gif</URL>
  <LandmarkPointListXml>
    <anyType xsi:type="LandmarkPointProperty">
      <LandmarkPointX>400</LandmarkPointX>
      <LandmarkPointY>292</LandmarkPointY>
      <LandmarkDesc>my room door</LandmarkDesc>
    </anyType>
    <anyType xsi:type="LandmarkPointProperty">
      <LandmarkPointX>399</LandmarkPointX>
      <LandmarkPointY>219</LandmarkPointY>
      <LandmarkDesc>bro room door</LandmarkDesc>
    </anyType>
  </LandmarkPointListXml>
  <RegionPointListXml />
</Map>

Python程序:

    def GetMapData(self):
        result = ""
        haha = self.XMLdoc.firstChild #root node
        for child in haha.childNodes:
            if (cmp(child.nodeName,'LandmarkPointListXml')==0):
                result = result + '|' + self.loopLandmark(child.childNodes) + '|'
            else:
                result = result + child.firstChild.nodeValue + ','
        return result

    def loopLandmark(self, landmarks):
        result=""
        haha=landmarks.getElementsByTagName('anyType')
        for child in haha.childNodes:
            if (cmp(haha.firstChild.nodeName,'LandmarkPointX') == 0):
                result=result+child.firstChild.nodeValue+','
                ChildNode = ChildNode.nextSibling
                result=result+child.firstChild.nodeValue+','
                ChildNode = ChildNode.nextSibling
                result=result+child.firstChild.nodeValue
        return result

我能够检索结果“er,er.gif,er,er.gif”，直到程序到达 <LandmarkPointListXml> .

Answer 1

这段代码非常脆弱。它对 XML 输入做出强有力的假设，如果以有效方式修改 XML(例如 if 不是紧接在 后面)，则会失败。

我建议在解析 XML 时使用标准库，例如 Element Tree ( http://docs.python.org/library/xml.etree.elementtree.html ) 或 lxml ( http://lxml.de )，它们也可以验证您的 XML 输入。

我在下面编写的代码使用元素树并适用于您的 XML 输入(我已删除了父类的“self”参数)。它还容忍(忽略)XML 元素中的空值。

import xml.etree.ElementTree as ET

def GetMapData( xmlfile ):
    result = ""
    try:
        tree = ET.parse( xmlfile )
    except IOError, e:
        print "Failure Parsing %s: %s" % (xmlfile, e)
    root = tree.getroot() # root node
    for child in root:
        if ( child.tag == 'LandmarkPointListXml' ):
            result += '|' + loopLandmark(child) + '|'
        elif child.text is not None:
            result += child.text + ','
    return result

def loopLandmark( landmarks ):
    result=""
    for landmark in landmarks:
        if ( landmark.tag == 'anyType' ): # check also xsi:type="LandmarkPointProperty"?
            for child in landmark:
                if ( child.text and child.tag in [ 'LandmarkPointX', 'LandmarkPointY' ] ):
                    result += child.text + ','
    return result

GetMapData( 'xml.in' )