设张三的mp3里有1000首歌，现在希望设计一种随机算法来随

#!/usr/bin/python
# -*- coding: utf-8 -*-

import random

l = [
 ('平凡之路', 89),
 ('夜空中最亮的星', 95),
]

s = reduce(lambda s, x: s + x[1], l, 0)

def rand_song():
    choose = random.randint(1, s)
    for song, weight in l:
        choose -= weight
        if choose <= 0:
            return song


if __name__ == '__main__':
 # test
 import time
 random.seed(time.time())
 d = {}
 for i in xrange(100000):
    song = rand_song()
    if song in d:
        d[song] += 1
    else:
        d[song] = 1
    for k, w in l:
        v = d[k]
        print k, v, 1.0*v/100000, 1.0*w/s

平凡之路 48092 0.48092 0.483695652174
夜空中最亮的星 51908 0.51908 0.516304347826