list, object and matching...

[Shagshag]

Hello, 

Newbie in python, not fluent in english...

Having a class with, for example, 3 private attributes a, b, c.
Having a python list (or maybe something which inherits from it) which
contains objects from this class.

How can i do to have :

- objecti == objectj only if attribute a and b are equal (c doesn't
need to be checked)

- list.index(objectk) => searching for an object contained in list but
which match only attribute a and b

Thanks in advance...