python 权重随机

weighted_random.py

import random
import bicsect
import itertools

class WeightedRandomGenerator(object):
    def __init__(self, weights):
        self.totals = []
        running_total = 0

        # py2
        for w in weights:
            running_total += w
            self.totals.append(running_total)
        # py3
        self.totals = list(itertools.accumulate(weights))

    def random(self):
        rnd = random.random() * self.totals[-1]
        return bisect.bisect_right(self.totals, rnd)

    def __call__(self):
        return self.random()