title: How to iterate through list in number of elements at once?
body: <p>For example, I have simple list like this:</p>
  
  <pre><code>l = [1,2,3,4,5,6,7,8,9]
  </code></pre>
  
  <p>I want to iterate over it in groups of 3 elements:</p>
  
  <pre><code>1,2,3
  4,5,6
  7,8,9
  </code></pre>
  
  <p>What is simplest way to do it? </p>