named tuples are classes, but they use __slots__ so they are sealed to extension thus using less memory. Take a look at the `namedtuple` source, it is a fun little bit of metaprogramming.

http://dev.svetlyak.ru/using-slots-for-optimisation-in-pytho...

http://hg.python.org/releasing/2.7.6/file/ba31940588b6/Lib/c...

I am wrong. namedtuple does NOT using slots. weird, wonder why?

Because it directly subclasses `tuple`

point = namedtuple("Point","x y z",verbose=True)

http://blip.tv/pycon-us-videos-2009-2010-2011/pycon-2011-fun...