title: Change text value with lxml
body: <p>I have an xml file - here is a snippet..</p>
  
  <pre><code>  &lt;gmd_fileIdentifier&gt;
      &lt;gco_CharacterString&gt;{0328cb65-b564-495a-b17e-e49e04864ab7}&lt;/gco_CharacterString&gt;
   &lt;/gmd_fileIdentifier&gt;
            &lt;gmd_identifier&gt;
              &lt;gmd_RS_Identifier&gt;
                &lt;gmd_authority gco_nilReason="missing" /&gt;
                &lt;gmd_code&gt;
                  &lt;gco_CharacterString&gt;0000&lt;/gco_CharacterString&gt;
                &lt;/gmd_code&gt;
                &lt;gmd_codeSpace xmlns:gml="http://www.opengis.net/gml" xmlns:msxsl="urn:schemas-microsoft-com:xslt"&gt;
                    &lt;gco_CharacterString&gt;test&lt;/gco_CharacterString&gt;
                  &lt;/gmd_codeSpace&gt;
              &lt;/gmd_RS_Identifier&gt;
            &lt;/gmd_identifier&gt;
  </code></pre>
  
  <p>What I want to do is change the value of 0000 which is currently in the                  tag,  to the gmd_fileIdentifier character string {0328cb65-b564-495a-b17e-e49e04864ab7}.</p>
  
  <p>I can access the values, using the following python code, but how do I set the value?
  Current code</p>
  
  <pre><code>import os, sys
  from lxml import etree
  
  myXML = r"D:\test.xml"
  tree = etree.parse(myXML)
  root = tree.getroot()
  root.xpath("//gmd_fileIdentifier/gco_CharacterString/text()")
  print fileID
  code = root.xpath("//gmd_identifier/gmd_RS_Identifier/gmd_code/gco_CharacterString/text()")
  print code
  </code></pre>
  
  <p>Thanks</p>