title: 3rd argument of python range
body: <p>I am trying to create a list of lists using a list comprehension method. I found this solution online:</p>
  
  <pre><code>output = [1,2,3,4,5,6]
  [output[i:i+2] for i in range(0, len(output), 2)]
  </code></pre>
  
  <p>This is the first time I have come across a 3rd argument in range, What does the 3rd argument of range do?</p>