title: try this in python shell: list.extend/append
body: <p>This is what I just did in python shell:</p>
  
  <pre><code>&gt;&gt;&gt;[1, 2]
  ...[1, 2]
  &gt;&gt;&gt;[1, 2].extend([2,3])  #when I pressed Enter
  &gt;&gt;&gt;  
  
                  #nothing came out
  </code></pre>
  
  <p>then I tried something else:</p>
  
  <pre><code>&gt;&gt;&gt;l = [1, 2]
  &gt;&gt;&gt;l
  ...[1, 2]
  &gt;&gt;&gt;m = [1, 2].extend([2, 3])
  &gt;&gt;&gt;m                     #pressed Enter, nothing came out
  &gt;&gt;&gt;m is None
  ...True
  </code></pre>
  
  <p>why?
  Does it mean, I cannot do something like</p>
  
  <pre><code>&gt;&gt;&gt;m = [...].extend(...)
  </code></pre>
  
  <p>?</p>