title: in Python, How to join a list of tuples into one list?
body: <p>Following on my previous question <a href="https://stackoverflow.com/questions/15266593/how-to-group-list-items-into-tuple">How to group list items into tuple?</a></p>
  
  <p>If I have a list of tuples, for example</p>
  
  <pre><code>a = [(1,3),(5,4)]
  </code></pre>
  
  <p>How can I unpack the tuples and reformat it into one single list</p>
  
  <pre><code>b = [1,3,5,4]
  </code></pre>
  
  <p>I think this also has to do with the <code>iter</code> function, but I really don't know how to do this. Please enlighten me.</p>