cathy

https://github.com/dfhoughton/cathy

Cathy lets you model an updatable weighted probability distribution which you can draw from. For example, suppose you want to randomly pull cards from a deck which consists only of aces, jacks, queens, and kings, with twice as many jacks as aces, twice as many queens as jacks, and twice as many kings as queens. Cathy will model this for you. And you can change the frequency of each card on the fly.