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python – Randomly picking Items with Given Probabilities

Posted by: admin May 14, 2020 Leave a comment

Questions:

Currently i’m working on a project where I need to code something in Python but stumbled upon some obstacles. I have an excel sheet with 692 items (stock keeping units) with their corresponding sales numbers. The items are in sequence from most sold till least sold. I calculated both the probability and cumulative probability for each item as can be seen in images 1 and 2 below:

excel sheet

excel sheet 2

Based on the cumulative probability and following formula: =INDEX(A$2:A$721;COUNTIF(H$2:H$721;”<=”&RAND())+1)

randomly 20 items are selected from the 692 items to generate an order picking list, which can be seen in the following image:

generated pick list

Basically i want to do the same in Python. Thus, select a number of items from a large list based on their probability.

I found the following code, but not sure how to use it:

    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

It would be great if someone could give me some directions in how to achieve this. Thanks in advance!

How to&Answers:

Use random.choices and give it some probabilities:

from collections import Counter
from random import choices


data = [1,2,3,4]
prob = [1,1,8,1] # 3 about 8 times more likely to being choosen then 1,2 or 4

c = Counter(choices(data,prob,k=1000)) # generate 1000 and count

print(c)

Output:

Counter({3: 717, 1: 101, 2: 92, 4: 90})  # 3 being taken far more often - about 8:1:1:1 if
                                         # you close both eyes and squint really hard ;)