title: Python regex split without empty string
body: <p>I have the following file names that exhibit this pattern:</p>
  
  <pre><code>000014_L_20111007T084734-20111008T023142.txt
  000014_U_20111007T084734-20111008T023142.txt
  ...
  </code></pre>
  
  <p>I want to extract the middle two time stamp parts after the second underscore <code>'_'</code> and before <code>'.txt'</code>. So I used the following Python regex string split:</p>
  
  <pre><code>time_info = re.split('^[0-9]+_[LU]_|-|\.txt$', f)
  </code></pre>
  
  <p>But this gives me two extra empty strings in the returned list:</p>
  
  <pre><code>time_info=['', '20111007T084734', '20111008T023142', '']
  </code></pre>
  
  <p>How do I get only the two time stamp information? i.e. I want:</p>
  
  <pre><code>time_info=['20111007T084734', '20111008T023142']
  </code></pre>