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  • Python 以指定的概率选取元素

    Python 以指定的概率选取元素

    Problem

    You want to pick an item at random from a list, just about as random.choice does, but you need to pick the various items with different probabilities given in another list, rather than picking any item with equal probability as random.choice does.

    Solution

    Module random in the standard Python library offers a wealth of possibilities for generating and using pseudo-random numbers, but it does not offer this specific functionality, so we must code it as a function of our own:

    import random 
    
    def random_pick(some_list, probabilities): 
        x = random.uniform(0,1) 
        cumulative_probability = 0.0 
        for item, item_probability in zip(some_list, probabilities): 
             cumulative_probability += item_probability 
             if x < cumulative_probability:
                   break 
        return item 

    random.uniform(0,1)->生成0.0到1.0之间的伪随机数,之后循环元素及其概率,计算累积概率.

    如:random_pick([1,2,3,4],[0.1,0.2,0.3,0.4])

    当x处于0.0到0.1之间,则输出1

    当x处于0.1到0.3之间,则输出2

    ……

    Example

    #以指定的概率获取元素 以一个列表为基准概率,从一个列表中随机获取元素 
    
    import random 
    
    def random_pick(some_list, probabilities): 
    x = random.uniform(0,1) 
    cumulative_probability = 0.0 
    for item, item_probability in zip(some_list, probabilities): 
    cumulative_probability += item_probability 
    if x < cumulative_probability:break 
    return item 
    
    some_list = [1,2,3,4] 
    probabilities = [0.2,0.1,0.6,0.1] 
    
    print random_pick(some_list,probabilities) 

    【注意】要求 some_list 的长度和 probabilities 的长度一致,以及所有元素的概率相加为1.0

    【References】

    [1] Randomly Picking Items with Given Probabilities

    [2] Python 以指定概率获取元素

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  • 原文地址:https://www.cnblogs.com/shenxiaolin/p/7810048.html
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