title: Python-way of getting a substring with a specified delimiter?
body: <p>Under a certain directory, I have a bunch of files with the name format:</p>
  
  <blockquote>
    <p>userName_description</p>
  </blockquote>
  
  <p>How may I extract the <code>userName</code> out?
  What about extracting the <code>description</code> out?</p>
  
  <p>I am wishing for a nice "Pythonic" way of achieving this.</p>