title: create nested dictionary one liner
body: <p>Hi I have three lists and I want to create a three-level nested dictionary using one line.</p>
  
  <p>i.e.,</p>
  
  <pre><code>l1 = ['a','b']
  l2 = ['1', '2', '3']
  l3 = ['d','e']
  </code></pre>
  
  <p>I'd want to create the following nested dictionary:</p>
  
  <pre><code>nd = {'a':{'1':{'d':0},{'e':0},'2':{'d':0},{'e':0},'3':{'d':0},{'e':0},'b':'a':{'1':{'d':0},{'e':0},'2':{'d':0},{'e':0},'3':{'d':0},{'e':0}}
  </code></pre>
  
  <p>I tried using zip to do the outer loop and add the lists but elements get replaced.  I.e., this does not work:</p>
  
  <pre><code>nd = {i:{j:{k:[]}} for i in zip(l1,l2,l3)}
  </code></pre>