使用lxml解析xml-提取元素值 [英] Parse xml with lxml - extract element value

问题描述

假设我们具有以下结构的XML文件.

Let's suppose we have the XML file with the structure as follows.

<?xml version="1.0" ?> 
<searchRetrieveResponse xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/zing/srw/ http://www.loc.gov/standards/sru/sru1-1archive/xml-files/srw-types.xsd" xmlns="http://www.loc.gov/zing/srw/">
  <records xmlns:ns1="http://www.loc.gov/zing/srw/">
    <record>
      <recordData>
        <record xmlns="">
          <datafield tag="000">
            <subfield code="a">123</subfield>
            <subfield code="b">456</subfield>
          </datafield>
          <datafield tag="001">
            <subfield code="a">789</subfield>
            <subfield code="b">987</subfield>
          </datafield>
        </record>
      </recordData>
    </record>
    <record>
      <recordData>
        <record xmlns="">
          <datafield tag="000">
            <subfield code="a">123</subfield>
            <subfield code="b">456</subfield>
          </datafield>
          <datafield tag="001">
            <subfield code="a">789</subfield>
            <subfield code="b">987</subfield>
          </datafield>
        </record>
      </recordData>
    </record>
  </records>
</searchRetrieveResponse>

我需要解析:

• 子字段"的内容(例如上例中的123)和
• 属性值(例如000或001)

我想知道如何使用lxml和XPath做到这一点.下面粘贴的是我的初始代码，我恳请某人向我解释如何解析值.

I wonder how to do that using lxml and XPath. Pasted below is my initial code and I kindly ask someone to explain me, how to parse out values.

import urllib, urllib2
from lxml import etree    

url = "https://dl.dropbox.com/u/540963/short_test.xml"
fp = urllib2.urlopen(url)
doc = etree.parse(fp)
fp.close()

ns = {'xsi':'http://www.loc.gov/zing/srw/'}

for record in doc.xpath('//xsi:record', namespaces=ns):
    print record.xpath("xsi:recordData/record/datafield[@tag='000']", namespaces=ns)

推荐答案

在您的XPath中，我会更直接:直接查找所需的元素，在这种情况下为datafield.

I would be more direct in your XPath: go straight for the elements you want, in this case datafield.

>>> for df in doc.xpath('//datafield'):
        # Iterate over attributes of datafield
        for attrib_name in df.attrib:
                print '@' + attrib_name + '=' + df.attrib[attrib_name]

        # subfield is a child of datafield, and iterate
        subfields = df.getchildren()
        for subfield in subfields:
                print 'subfield=' + subfield.text

此外，lxml似乎可以让您忽略名称空间，也许是因为您的示例仅使用一个名称空间?

Also, lxml appears to let you ignore the namespace, maybe because your example only uses one namespace?

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