title: How to separate by comma all the elements of a nested list?
body: <p>I have a long list with tokens like this:</p>
  
  <pre><code> a_lis = [['hi how are you'],
  ['im fine thanks'],
  ['cool lets go to the restaurant']
  ,...,
  ['I can't now']]
  </code></pre>
  
  <p>I would like to separate each token or term with a comma like this (*):</p>
  
  <pre><code> a_lis = [['hi', 'how', 'are', 'you'],
  ['im', 'fine', 'thanks'],
  ['cool', 'lets', 'go', 'to', 'the', 'restaurant']
  ,...,
  ['I', 'can't', 'now']]
  </code></pre>
  
  <p>I tried to:</p>
  
  <pre><code>[x.replace(' ', ', ') for x in a_lis]
  </code></pre>
  
  <p>However, is not working. Amy idea of how to get (*)?</p>