title: Building advanced list combinations
body: <p>I have 2 lists that are similar to this format:</p>
  
  <pre><code>a= [1,2,3]
  b= [1,2,3,4,5,6]
  </code></pre>
  
  <p>I am looking to pair the lists in this particular format:</p>
  
  <p>In [a,b] format:</p>
  
  <pre><code>[1,1]
  [2,2]
  [3,3]
  [1,4]
  [2,5]
  [3,6]
  </code></pre>
  
  <p>I have read about numpy and itertools handling similar cases but I'm a little stuck in this case.</p>
  
  <p>Thanks.</p>
  
  <p>I'm not looking for itertools.izip_longest because I do not want None values. Everything must be paired as indicated in the example, above.</p>