python - Problems parsing an XML file with xml.etree.ElementTree -

i have parse xml files contain entries like

<error code="unknowndevice">     <description /> </error> 

which defined elsewhere as

<group name="error definitions">      <errordef id="0x11" name="unknowndevice">         <description>indicated device unknown</description>      </errordef>      ... </group> 

given

import xml.etree.elementtree et  parser = et.xmlparser() parser.parser.useforeigndtd(true)  tree = et.parse(inputfilename, parser=parser) root = tree.getroot() 

how can values errordef? mean value of id , of description?

how can search & extract values, using unknowndevice?

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[update] error groups have differing names, of format "xxx error definitions", "yyy error definitions", etc

further, seem nested @ different depths in different documents.

given error's title, e.g "unknowndevice", how can search under root corresponding id , description values?

can go directly them, using e.g "unknowndevice", or have search first error groups?

if have this:

<group name="error definitions">      <errordef id="0x11" name="unknowndevice">         <description>indicated device unknown</description>      </errordef>      ... </group> 

and want value of description , id every errordef element, this:

for err in tree.xpath('//errordef'):     print err.get('id'), err.find('description').text 

which give like:

0x11 indicated device unknown