Talk is cheap, show me the code.

random_demo.py程式碼如下:

# coding: utf-8
import random

def random_index(rate):
    """隨機變數的概率函式"""
    #
    # 引數rate為list<int>
    # 返回概率事件的下標索引
    start = 0
    index = 0
    randnum = random.randint(1, sum(rate))

    for index, scope in enumerate(rate):
        start += scope
        if
 
 randnum <= start:
            break
    return index

def main():
    arr = ['red', 'green', 'blue']
    rate = [45, 30, 25]

    red_times = 0
    green_times = 0
    blue_times = 0
    for i in xrange(10000):
        if arr[random_index(rate)] == 'red':
            red_times += 1
        if arr[random_index(rate)] == 'green'
 
:
            green_times += 1
        if arr[random_index(rate)] == 'blue':
            blue_times += 1

    print red_times, green_times, blue_times

if __name__ == '__main__':
    main()

列印結果:

$ python random_demo.py 
4507 3009 2537
$ python random_demo.py 
4586 3055 2485
$ python random_demo.py 
4483
 
 2996 2506
$ python random_demo.py 
4586 3015 2480
$ python random_demo.py 
4513 3057 2415
$ python random_demo.py 
4494 3014 2456
$ python random_demo.py 
4502 2978 2505
$ python random_demo.py 
4475 3041 2528
$ python random_demo.py 
4561 3043 2520
$ python random_demo.py 
4558 2923 2474
$ python random_demo.py 
4536 2957 2535
$ python random_demo.py 
4526 2985 2576
$ python random_demo.py 
4532 2936 2547
$ python random_demo.py 
4420 2908 2447

可以看到結果, 抽中紅綠藍的次數非常接近它們的概率比例45:30:25, 其中random_index(rate)函式為核心程式碼.

OK, Enjoy it~