Python - random.choices() method

Last Updated : 05 Dec, 2024

The choices() method returns multiple random elements from the list with replacement. Unlike random.choice(), which selects a single item, random.choices() allows us to select multiple items making it particularly useful for tasks like sampling from a population or generating random data.

Example:

Python

import random

a = ["geeks", "for", "python"]

print(random.choices(a, weights = [10, 1, 1], k = 5))

Output

['geeks', 'geeks', 'geeks', 'geeks', 'geeks']

Explanation:

The code uses random.choices() to select 5 items from the list a = ["geeks", "for", "python"].
Weights: The item "geeks" has a weight of 10, making it 10 times more likely to be selected than "for" and "python", which each have a weight of 1.
k = 5: Specifies that 5 items will be selected, with replacement (meaning duplicates are possible).

Note: Every time output will be different as the system returns random elements.

Let's take a closer look at random.choices() method:

Table of Content

Syntax of random.choices()
random.choices(population, weights=None, cum_weights=None, k=1)
Parameters
population: The sequence (list, tuple, string, etc.) from which random selections are made.
weights: (Optional) A sequence of weights corresponding to each element in the population. Elements with higher weights are more likely to be selected.
cum_weights: (Optional) A sequence of cumulative weights. If provided, this is an alternative to using the weights parameter.
k: The number of items to return. By default, it returns one item.

Example of random.choices() method:

Python

import random

# Example 1: Simple Random Selection

a = ['apple', 'banana', 'cherry', 'date']
res = random.choices(a, k=3)
print(res)  



# Example 2: Random Selection with Weights

w = [10, 20, 5, 1]
res = random.choices(a, weights=w, k=3)
print(res)  

# Example 3: Random Selection with Cumulative Weights

cw = [10, 30, 35, 36]  # Cumulative sum of weights
res = random.choices(a, cum_weights=cw, k=3)
print(res)  

# Example 4: Selecting Random Characters from a String

ch = "abcdefghijklmnopqrstuvwxyz"
res = random.choices(ch, k=5)
print(res)

Output

['cherry', 'apple', 'apple']
['cherry', 'banana', 'banana']
['cherry', 'cherry', 'banana']
['c', 'd', 'm', 'z', 's']

Explanation:

Example 1: Selects 3 random elements from the items list.
Example 2: Selects 3 elements from items with specified weights, making some items more likely to be selected.
Example 3: Selects 3 elements with cumulative weights, ensuring that selection probabilities are proportionally distributed.
Example 4: Selects 5 random characters from the alphabet string, demonstrating the flexibility of random.choices() with strings.

Practical Applications of random.choices() method:

It allows for sampling with replacement, meaning the same item can be selected multiple times. Common practical applications include:

Lottery or Prize Draws: Randomly selecting winners from a pool of entries, where some participants may have more chances based on certain conditions.
Simulating Weighted Outcomes: For example, simulating biased coin flips or biased random events (e.g., selecting between different items in a game where certain items are rarer).
Random Sampling: Selecting items from a list for tasks like A/B testing, survey sampling, or testing combinations.