title: Group one list of string elements based on another list
body: <p>I want to group by my_list based on another list keys as follows: </p>
  
  <pre><code>my_list = ['apple_2010', 'banana_2010', 'carrot_2010', 'dog_2011', 'eye_2011', 'fig_2011']
  
  keys = ['2010','2010','2010','2011','2011','2011']
  
  for x,y in zip(my_list,keys):
  
  ???
  </code></pre>
  
  <p>The expected answer is:</p>
  
  <pre><code>answer = [['apple_2010', 'banana_2010', 'carrot_2010'],
   ['dog_2011', 'eye_2011', 'fig_2011']]
  </code></pre>