Find and Replace Values in XML using Python

Question

I am looking to edit XML files using python. I want to find and replace keywords in the tags. In the past, a co-worker had set up template XML files and used a "find and replace" program to replace these key words. I want to use python to find and replace these key words with values. I have been teaching myself the Elementtree module, but I am having trouble trying to do a find and replace. I have attached a snid-bit of my XML file. You will seen some variables surrounded by % (ie %SITEDESCR%) These are the words I want to replace and then save the XML to a new file. Any help or suggestions would be great.

Thanks, Mike

<metadata> <idinfo> <citation> <citeinfo>  <origin>My Company</origin>  <pubdate>05/04/2009</pubdate>  <title>POLYGONS</title>  <geoform>vector digital data</geoform>  <onlink>\\C$\ArcGISDevelopment\Geodatabase\PDA_STD_05_25_2009.gdb</onlink> </citeinfo> </citation>  <descript>  <abstract>This dataset represents the mapped polygons developed from the field data for the %SITEDESCR%.</abstract>  <purpose>This dataset was created to accompany some stuff.</purpose>  </descript> <timeperd> <timeinfo> <rngdates>  <begdate>%begdate%</begdate>  <begtime>unknown</begtime>  <enddate>%enddate%</enddate>  <endtime>unknown</endtime>  </rngdates>  </timeinfo>  <current>ground condition</current>  </timeperd> 

Answer 1

The basics:

from xml.etree import ElementTree as et tree = et.parse(datafile) tree.find('idinfo/timeperd/timeinfo/rngdates/begdate').text = '1/1/2011' tree.find('idinfo/timeperd/timeinfo/rngdates/enddate').text = '1/1/2011' tree.write(datafile) 

You can shorten the path if the tag name is unique. This syntax finds the first node at any depth level in the tree.

tree.find('.//begdate').text = '1/1/2011' tree.find('.//enddate').text = '1/1/2011' 

Also, read the documentation, esp. the XPath support for locating nodes.

Answer 2

If you just want to replace the bits enclosed with %, then this isn't really an XML problem. You can easily do it with regex:

import re xmlstring = open('myxmldocument.xml', 'r').read() substitutions = {'SITEDESCR': 'myvalue', ...} pattern = re.compile(r'%([^%]+)%') xmlstring = re.sub(pattern, lambda m: substitutions[m.group(1)], xmlstring)