ListMixin (WAS: How do you control _all_ items added to a list?)

[Steven Bethard]

Nick Coghlan wrote:
 > Hmm, it might be nice if there was a UserList.ListMixin that was the
 > counterpart to UserDict.DictMixin

I've thought this occasionally too.  One of the tricky issues though is 
that often you'd like to define __getitem__ for single items and have 
ListMixin add the code for slices.  I haven't figured out how to do this 
cleanly yet...

STeVe