title: Python 2.7 append values to dictionary
body: <p>I have 2 dictionaries with identical keys.</p>
  
  <pre><code>d1 = {'Dog':[7,2],'Cat':[5,2]}
  d2 = {'Dog':1,'Cat':4}
  </code></pre>
  
  <p>Is there a good way of combining them so that I can have one dictionary that looks like this?</p>
  
  <pre><code>d = {'Dog':[7,2,1],'Cat':[5,2,4]}
  </code></pre>