title: Why invoking ElementTree.parse function twice in one script will get an exception?
body: <p>I need to process two xml files in one script.
  So, I wrote some codes like below:</p>
  
  <pre><code>import xml.etree.cElementTree as ET
  
  parser = ET.XMLParser(encoding='utf-8')
  ET.parse('../wiki.xml', parser=parser)
  ET.parse('../tutorial.xml', parser=parser)
  </code></pre>
  
  <p>However, the second call <code>parse</code> got an exception.</p>
  
  <pre><code>cElementTree.ParseError: parsing finished
  </code></pre>
  
  <p>But, I ensure that both xml files have no inner problems, because when I changed the order the second invoke always got an exception and if I reserved one there was no problem.  </p>
  
  <p>So, why invoking ElementTree.parse function twice in one script will get an exception?</p>