title: To merge two dictionaries of list in Python
body: <p>There are two dictionaries </p>
  
  <pre><code>x={1:['a','b','c']}
  y={1:['d','e','f'],2:['g']}
  </code></pre>
  
  <p>I want another dictionary z which is a merged one of x and y such that</p>
  
  <pre><code>z = {1:['a','b','c','d','e','f'],2:['g']}
  </code></pre>
  
  <p>Is it possible to do this operation? 
  I tried update operation </p>
  
  <pre><code>x.update(y)
  </code></pre>
  
  <p>But it gives me the following result</p>
  
  <pre><code>z= {1:['d','e','f'],2:['g']}
  </code></pre>