title: Slicing strings omits letters at end
body: <p>Given a string <code>abcdefghi</code> and a distance 3, I'm splitting it in this manner:</p>
  
  <pre><code>st = 'abcdefghi'
  substrings = []
  for i in range(3): 
      substrings.append(st[::3])
      st = st[1:]
  </code></pre>
  
  <p>Which should ideally give me:</p>
  
  <pre><code>String 1: adg
  String 2: beh
  String 3: cfi
  </code></pre>
  
  <p>But instead, under my method, the last alphabet (or more if the string is longer) gets omitted ie. <code>String 3: cf</code></p>
  
  <p>How do I fix the corner case?</p>
  
  <p><strong>EDIT:</strong> The example string here is too small to reproduce the error. A much longer string would reproduce the error. </p>