How to do weighted random sample of categories in python

Question

Given a list of tuples where each tuple consists of a probability and an item I\'d like to sample an item according to its probability. For example, give the list [ (.3, \'a\'),

Answer 1

I'm not sure if this is the pythonic way of doing what you ask, but you could use random.sample(['a','a','a','b','b','b','b','c','c','c'],k) where k is the number of samples you want.

For a more robust method, bisect the unit interval into sections based on the cumulative probability and draw from the uniform distribution (0,1) using random.random(). In this case the subintervals would be (0,.3)(.3,.7)(.7,1). You choose the element based on which subinterval it falls into.