list organization question

[Robocop]

I have a list of objects, each object having two relevant attributes:
date and id.  I'd like not only organize by id, but also by date.
I.e. i would like to parse my list into smaller lists such that each
new mini-list has a unique date, but consists of only objects with a
specific id.  Are there any handy imports i could use to accomplish
something like this?  I'm relatively new to python and as such don't
know all of the preloaded functions at my disposal.  Thanks for any
help in advance, the community here is always ridiculously helpful.