title: Selecting List Elements Periodically in Python 3
body: <p>Say I have a list </p>
  
  <pre><code>Q = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]
  </code></pre>
  
  <p>I believe I can extract the first and every ninth value thereafter using the extended slice notation:</p>
  
  <pre><code>Q[::9]
  </code></pre>
  
  <p>Which should give:</p>
  
  <pre><code>[0,9,18]
  </code></pre>
  
  <p>But how can I similarly select all the elements <em>apart from</em> those?</p>