title: Appending turns my list to NoneType
body: <p>In Python Shell, I entered:  </p>
  
  <pre><code>aList = ['a', 'b', 'c', 'd']  
  for i in aList:  
      print(i)
  </code></pre>
  
  <p>and got  </p>
  
  <pre><code>a  
  b  
  c  
  d  
  </code></pre>
  
  <p>but when I tried:  </p>
  
  <pre><code>aList = ['a', 'b', 'c', 'd']  
  aList = aList.append('e')  
  for i in aList:  
      print(i) 
  </code></pre>
  
  <p>and got  </p>
  
  <pre><code>Traceback (most recent call last):  
    File "&lt;pyshell#22&gt;", line 1, in &lt;module&gt;  
      for i in aList:  
  TypeError: 'NoneType' object is not iterable  
  </code></pre>
  
  <p>Does anyone know what's going on? How can I fix/get around it?</p>