title: List Comprehension of Lists Nested in Dictionaries
body: <p>I have a dictionary where each value is a list, like so: </p>
  
  <pre><code>dictA = {1:['a','b','c'],2:['d','e']}
  </code></pre>
  
  <p>Unfortunately, I cannot change this structure to get around my problem</p>
  
  <p>I want to gather all of the entries of the lists into one single list, as follows:</p>
  
  <pre><code>['a','b','c','d','e']
  </code></pre>
  
  <p>Additionally, I want to do this only once within an if-block.  Since I only want to do it once, I do not want to store it to an intermediate variable, so naturally, a list comprehension is the way to go.  But how?  My first guess,</p>
  
  <pre><code>[dictA[key] for key in dictA.keys()]
  </code></pre>
  
  <p>yields,</p>
  
  <pre><code>[['a','b','c'],['d','e']]
  </code></pre>
  
  <p>which does not work because </p>
  
  <pre><code>'a' in  [['a','b','c'],['d','e']]
  </code></pre>
  
  <p>yields <code>False</code>.  Everything else I've tried has used some sort of illegal syntax.</p>
  
  <p>How might I perform such a comprehension?</p>