title: How to double all the values in a list
body: <pre><code>n = [3, 5, 7]
  
  def double(lst):
      for x in lst:
          x *= 2
          print x
      return lst
  
  print double(n)
  </code></pre>
  
  <p>Why doesn't this return <code>n = [6, 10, 14]</code>?</p>
  
  <p>There should also be a better solution that looks something like <code>[x *=2 for x in lst]</code> but it doesn't work either.</p>
  
  <p>Any other tips about for-loops and lists would be much appreciated.</p>