What attributes are not stored in __dict__ and why are they not?
<p>In Python, a lot of the "special" attributes of objects are stored in the <code>__dict__</code> dictionary, like <code>__doc__</code>, <code>__module__</code> (from what I could see in my experiments).</p>

<p>However some are not, like <code>__class__</code>. My question is exactly which attributes are not stored in <code>__dict__</code> (is that even documented somewhere?), and why are they not?</p>
