?Combination of a Dictionary and a List?

[Norman Shelley]

Sometime  in the past I wrote a simple combination of a dictionary and a
list, where __getitem__() would first look in a hidden dictionary and
then if not found it would try looking in a hidden list.  I've seen this
type of code out there somewhere also but I can not find my code or
anyone elses. I guess I haven't figure our the "right" search criteria
on www.python.org.  Any pointers?