title: Python slicing explained
body: <p>OK I understand the basics, but can someone explain code copied from Greg's answer <a href="https://stackoverflow.com/questions/509211/understanding-pythons-slice-notation">here</a>:</p>
  
  <pre><code>a[1::-1]   # the first two items, reversed
  a[:-3:-1]  # the last two items
  a[-3::-1]  # everything except the last two items, reversed
  </code></pre>
  
  <p>To me the first one reads: slice from 2nd position to end, then reverse it.</p>
  
  <p>The second one is slice from beginning to the -2 position then reverse it.</p>
  
  <p>The third one is slice from -3rd position to end then reverse it.</p>
  
  <p>Obviously I am wrong since they work as suggested, but can you please tell me why?</p>