title: python lxml: case insensitive xpath tag name matching
body: <p>I'm using python + lxml to parse a spss file. </p>
  
  <p>There seems to be many threads on this topic but the answers don't particular help me. </p>
  
  <p>The answers I have come across:</p>
  
  <pre><code>- lower-case the entire input before parsing; 
  - if you know the complete list of tags in advance
  </code></pre>
  
  <p>For me these suggestion would take too much time. </p>
  
  <p>Instead I would like to match strings only when necessary. </p>
  
  <p>Here is the line of code I would like to edit:</p>
  
  <pre><code>xpath("//definition//variable[@name='"+tag_name+"']")
  </code></pre>
  
  <p>How can I get a hit if tag_name is:</p>
  
  <pre><code>tag_name = "Q1top"
  tag_name = "q1Top"
  tag_name = "q1TOP"
  etc
  </code></pre>
  
  <p>I'm guessing some form of regex would be in order???</p>