如何随机选择列表的值? [英] How to randomly select values for a list?

问题描述

我使用的是 Python 2.7

I'm using Python 2.7

明确地说，我不想随机化列表中的项目.我想这样做，以便某些字符串可能根本不显示.例如:

To be clear, I don't want to randomize the items in the list. I want to make it so it's possible for certain strings not to show up at all. For example:

    r = "red"
    b = "blue"
    y = "yellow"
    rc = random colour
    myColours = [rc,rc,rc]
    print myColours

显然上面的代码不起作用，但我不确定如何继续.如果我可以更改某个字符串被选中的可能性，例如 50% 的红色几率、30% 的蓝色几率和 20% 的黄色几率，这也会有所帮助.

Obviously the code above wouldn't work, but I'm not sure how to proceed. It would also help if I could change how likely a certain string would be selected, like 50% odds of red, 30% odds of blue, and 20% odds of yellow.

推荐答案

您可以使用 numpy.random.choice.p 参数允许您指定与每个条目关联的概率.

You can use numpy.random.choice. The p parameter allows you to specify the probabilities associated with each entry.

import numpy as np

r, b, y = 'red', 'blue', 'yellow'
my_colours = np.random.choice(a=[r, b, y], size=3, p=[.5, .3, .2])
print(my_colours) . # my_colours.tolist() if you want list output
# ['yellow' 'red' 'red']

要确认这是有效的，请使用大小为 30,000 而不是 3 的结果，并让大数定律发挥作用.

To confirm this is working, use a result of size 30,000 rather than 3 and let the law of large numbers do its thing.

from collections import Counter

test = np.random.choice(a=[r, b, y], size=30000, p=[.5, .3, .2])
counts = Counter(test)

# Relative occurences:
dict(zip(counts.keys(), [count/30000 for count in counts.values()]))
{'blue': 0.30483333333333335,
 'red': 0.5000333333333333,
 'yellow': 0.19513333333333333}

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