Given an array of elements which are composed of a tuple of a string label and integer weight, chooses one randomly while factoring in the relative weightings, and returns the label.

choose_weighted.py

from bisect import bisect
from random import random
def weighted_choice(choices):
	values, weights = zip(*choices)
	total = 0
	cum_weights = []
	for w in weights:
		total += w
		cum_weights.append(total)
	guess = random () * total
	index = bisect(cum_weights, guess)
	return values[index]

def main():
	my_choices = [('a',1),('b',0),('c',2),('d',3),('e',0)]
	my_results = []
	for i in range (6000):
		answer = weighted_choice(my_choices)
		my_results.append(answer)
	print("A:{}\nB:{}\nC:{}\nD:{}\nE:{}\n".format(
			my_results.count('a'),
			my_results.count('b'),
			my_results.count('c'),
			my_results.count('d'),
			my_results.count('e')))

if __name__ == "__main__":
	main()