Python LXML：如何使用XPath选择器获取XML标签名称？

Question

I'm trying to parse the following XML using Python and lxml :

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="/bind9.xsl"?>
<isc version="1.0">
  <bind>
    <statistics version="2.2">
      <memory>
        <summary>
          <TotalUse>1232952256
          </TotalUse>
          <InUse>835252452
          </InUse>
          <BlockSize>598212608
          </BlockSize>
          <ContextSize>52670016
          </ContextSize>
          <Lost>0
          </Lost>
        </summary>
      </memory>
    </statistics>
  </bind>
</isc>

The goal is to extract the tag name and text of every element under bind/statistics/memory/summary in order to produce the following mapping:

TotalUse: 1232952256
InUse: 835252452
BlockSize: 598212608
ContextSize: 52670016
Lost: 0

I've managed to extract the element values, but I can't figure out the xpath expression to get the element tag names.

A sample script:

from lxml import etree as et

def main():

    xmlfile = "bind982.xml"
    location = "bind/statistics/memory/summary/*"
    label_selector = "??????" ## what to put here...?
    value_selector = "text()"

    with open(xmlfile, "r") as data:
        xmldata = et.parse(data)

        etree = xmldata.getroot()

        statlist = etree.xpath(location)

        for stat in statlist:
            label = stat.xpath(label_selector)[0]
            value = stat.xpath(value_selector)[0]
            print "{0}: {1}".format(label, value)

if __name__ == '__main__':
    main()

I know I could use value = stat.tag instead of stat.xpath() , but the script must be sufficiently generic to also process other pieces of XML where the label selector is different.

What xpath selector would return an element's tag name?

Answer 1

Simply use XPath's name() , and remove the zero index since this returns a string and not list.

from lxml import etree as et

def main():

    xmlfile = "ExtractXPathTagName.xml"
    location = "bind/statistics/memory/summary/*"
    label_selector = "name()"                         ## what to put here...?
    value_selector = "text()"

    with open(xmlfile, "r") as data:
        xmldata = et.parse(data)

        etree = xmldata.getroot()

        statlist = etree.xpath(location)

        for stat in statlist:
            label = stat.xpath(label_selector)
            value = stat.xpath(value_selector)[0]
            print("{0}: {1}".format(label, value).strip())

if __name__ == '__main__':
    main()

Output

TotalUse: 1232952256    
InUse: 835252452    
BlockSize: 598212608    
ContextSize: 52670016    
Lost: 0

Answer 2

I think you don't need XPath for the two values, the element nodes have properties tag and text so use for instance a list comprehension:

[(element.tag, element.text) for element in etree.xpath(location)]

Or if you really want to use XPath

result = [(element.xpath('name()'), element.xpath('string()')) for element in etree.xpath(location)]

You could of course also construct a list of dictionaries:

result = [{ element.tag : element.text } for element in root.xpath(location)]

or

result = [{ element.xpath('name()') : element.xpath('string()') } for element in etree.xpath(location)]