Cannot append to a returned list?
<pre><code>def f():
    lst = ['a', 'b', 'c']
    return lst[1:]
</code></pre>

<p>why is <code>f().append('a') is None == True</code> even though <code>f().__class__</code> is <code>&lt;type 'list'&gt;</code> and <code>f() == ['b', 'c']</code></p>
