title: Python: Write two lists into two column text file
body: <p>Say I have two lists:
  a=[1,2,3]
  b=[4,5,6]
  I want to write them into a text file such that I obtain a two column text file:</p>
  
  <pre class="lang-html prettyprint-override"><code>1 4
  2 5
  3 6
  </code></pre>