title: Python list error: [::-1] step on [:-1] slice
body: <p>I thought I understood the basics of list slicing in python, but have been receiving an unexpected error while using a negative step on a slice, as follows:</p>
  
  <pre><code>&gt;&gt;&gt; a = list(range(10))
  &gt;&gt;&gt; a
  [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  &gt;&gt;&gt; a[:-1]
  [0, 1, 2, 3, 4, 5, 6, 7, 8]
  &gt;&gt;&gt; a[::-1]
  [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
  &gt;&gt;&gt; a[:-1:-1]
  []
  </code></pre>
  
  <p>(Note that this is being run in Python 3.5)</p>
  
  <p>Why doesn't a[:-1:-1] reverse step through the a[:-1] slice in the same manner as it does through the whole list with a[::-1]? </p>
  
  <p>I realize that you can use list.reverse() as well, but trying to understand the underlying python slice functionality better. </p>