Style guide for subclassing built-in types?

[janeaustine50 at hotmail.com]

Jane Austine wrote:
> Please see the following code:
> --------------------------------
> class rev_wrap(object):
>     def __init__(self,l):
>         self.l=l
>     def __getitem__(self,i):
>         return self.l[-i-1]
>
> class rev_subclass(list):
>     def __getitem__(self,i):
>         return list.__getitem__(self,-i-1)
>
> if __name__=='__main__':
>     l=rev_wrap([1,2,3])
>     assert l[0]==3
>     assert list(l)==[3,2,1]
>
>     l=rev_subclass([1,2,3])
>     assert l[0]==3
>     assert list(l)==[3,2,1]

Oh... I forgot one. assert l==[3,2,1] at this point doesn't pass
either. "print l" outputs the wrong one([1,2,3]) as well.