带概率的Python随机列表索引

如何编写一个函数，根据列表中的概率给出列表元素的随机索引

列表如下所示，包含5个元素

a = [0.1, 0.2, 0.4, 0.2, 0.1]

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有没有简单快速的解决方案？谢谢

如果您有NumPy，它可能会更快，但如果没有，这里有一个纯Python解决方案

from random import random

a = [0.1, 0.2, 0.4, 0.2, 0.1]

def randombin(bins):
    r = random()
    p = 0
    for i, v in enumerate(bins):
        p += v
        if r < p:
           return i
    # p may not equal exactly 1.0 due to floating-point rounding errors
    # so if we get here, just try again (the errors are small, so this
    # should not happen very often).  You could also just put it in the
    # last bin or pick a bin at random, depending on your tolerance for
    # small biases
    return randombin(bins)

print randombin(a)

从随机导入随机
a=[0.1,0.2,0.4,0.2,0.1]
def随机箱（箱）：
r=随机（）
p=0
对于枚举中的i、v（箱）：
p+=v
如果r

这听起来像是的作业，其

p

参数：

因此，如果只有一个列表（其中一个元素既是每个元素的概率，也是要选择的元素本身），您可以这样做：

from numpy.random import choice

elementsAndProbabilities = [0.1, 0.2, 0.4, 0.2, 0.1]

randomElement = choice(elementsAndProbabilities, p=elementsAndProbabilities)
print randomElement

from numpy.random import choice

elements = ["first", "second", "third", "fourth", "fifth"]
probabilities = [0.1, 0.2, 0.4, 0.2, 0.1]    

randomElement = choice(elements, p=probabilities)
print randomElement

from numpy.random import choice

probabilities = [0.1, 0.2, 0.4, 0.2, 0.1]

randomElement = choice(range(len(probabilities)), p=probabilities)
print randomElement

如果您有一个元素列表和每个元素的概率列表（单独），您可以这样做：

from numpy.random import choice

elementsAndProbabilities = [0.1, 0.2, 0.4, 0.2, 0.1]

randomElement = choice(elementsAndProbabilities, p=elementsAndProbabilities)
print randomElement

from numpy.random import choice

elements = ["first", "second", "third", "fourth", "fifth"]
probabilities = [0.1, 0.2, 0.4, 0.2, 0.1]    

randomElement = choice(elements, p=probabilities)
print randomElement

from numpy.random import choice

probabilities = [0.1, 0.2, 0.4, 0.2, 0.1]

randomElement = choice(range(len(probabilities)), p=probabilities)
print randomElement

现在，你说你想要的是索引，而不是元素，所以我们可以得到如下索引：

from numpy.random import choice

elementsAndProbabilities = [0.1, 0.2, 0.4, 0.2, 0.1]

randomElement = choice(elementsAndProbabilities, p=elementsAndProbabilities)
print randomElement

from numpy.random import choice

elements = ["first", "second", "third", "fourth", "fifth"]
probabilities = [0.1, 0.2, 0.4, 0.2, 0.1]    

randomElement = choice(elements, p=probabilities)
print randomElement

from numpy.random import choice

probabilities = [0.1, 0.2, 0.4, 0.2, 0.1]

randomElement = choice(range(len(probabilities)), p=probabilities)
print randomElement

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我想这就是你要找的：不是重复的。这个问题有一些不同的细节。