title: remove element in list in a dictionary
body: <p>In a big dictionary, similar to</p>
  <pre><code>d = {}                                                                                   
  d['a']=[1,2,3,4]                                                                         
  d['b']=[1,2,3,4,5,6]                                                                     
  d['c']=[1,2]                                                                             
  d['d']=[1,4]
  </code></pre>
  <p>how can I quickly remove the 'four' in the lists ?</p>
  <h3>EDIT</h3>
  <p>Is there a way to link the fours in the lists? As in, eliminating one eliminates the others.</p>