None

[Skip Montanaro]

    >>> None = 17
    >>> print None
    17

    Werner> Strange... is it intended that you can assign to None?

It's just another symbol.

    Werner> In short, is this a bug or a feature?

Neither.  You can also override sys.stdout, sys.args, __builtins__.int,
etc. 

-- 
Skip Montanaro (skip at pobox.com)
http://www.mojam.com/
http://www.musi-cal.com/