title: Merge 3 lists defined by 1 variable
body: <p>I have a text (simplified):</p>
  <p>a b c d</p>
  <p>e f g</p>
  <p>Then I have this code (MapReduce):</p>
  <pre class="lang-py prettyprint-override"><code>import sys
  for line in sys.stdin:
      words = line.strip().split()
      print(words)
  </code></pre>
  <p>The variable <em>words</em> gives me:</p>
  <pre class="lang-py prettyprint-override"><code>['a', 'b', 'c', 'd']
  []
  ['e', 'f', 'g']
  </code></pre>
  <p><strong>How to get:</strong></p>
  <pre class="lang-py prettyprint-override"><code>['a', 'b', 'c', 'd', 'e', 'f', 'g']
  </code></pre>
  <p>Thanks!</p>