How can I randomly select an item from a list?

python

random-selection

secrets-module

list-manipulation

byAlex Kataev·Aug 15, 2024

To randomly pick an item from a list in Python, use random.choice().

The example below demonstrates its proper usage:

import random
item = random.choice(['apple', 'banana', 'cherry'])  # Expect any of these fruits. Surprise! 🎉

Diving deeper: Advanced random selection methods

Python is rich in tools for picking random elements. Let's go through some of the most frequently used ones, categorized by their use cases.

When you're handling sensitive data 🕵️‍♀️

Python's secrets module offers cryptographically strong randomness, ideal for picking random entries from lists containing sensitive information.

import secrets
secure_item = secrets.choice(['secret1', 'secret2', 'secret3'])  # Shhh! It's a secret! 🤫

Python version compatibility 🐍

For codebases running on Python versions prior to 3.6, use random.SystemRandom().choice() for a more secure random choice.

import random
sys_random = random.SystemRandom()  
secure_item_pre36 = sys_random.choice(['option1', 'option2', 'option3'])  # Time travelling to Python Jurassic 🦖

Multiple distinct items selected randomly 🎰

random.sample() can be used to select multiple distinct elements randomly.

import random
items = random.sample(['a', 'b', 'c', 'd'], 2)  # Double the fun! 🎈🎈

Better still, you can select two items succinctly. Let's try this,

first, second = random.sample(['apple', 'banana', 'cherry'], 2)  # Fruit salad, anyone? 🍏🍌

Sets, but make them random 👾

Types unsupported directly by random.choice(), such as sets, can be converted to lists or tuples:

# Sets are like the honey badgers of Python. They just don't care (for order)! 😆
import random
random_item_from_set = random.choice(tuple({1, 2, 3}))  # Convert the set to a tuple, then pick a number 🎰

Randomized indexing with randrange 🔢

When you need a random index to retrieve the element, randrange() generates a random index within the list length range.

from random import randrange
idx = randrange(len(my_list))  # Surprise me, Python! 
random_item_via_index = my_list[idx]  # Who will be the chosen one? 🎁

Pointers for pythonic randomness

Choose simplicity, unless stronger security measures are needed. random.choice() is usually sufficient, but sensitive applications call for secrets.choice(). When you need multiple items without repeats, random.sample() comes to the rescue.

Navigating through randomness: Exploring edge cases 🧭

Edge cases in lists can call for extra steps before random selection.

Uneven odds 🎲

Weight the odds in favor of certain list items using random.choices():

# Pick a fight outcome. Spoiler: You more likely to win! 💪
import random
weighted_item = random.choices(['Win', 'Lose', 'Draw'], weights=[10, 1, 1], k=1)[0]

For non-list iterables 🔄

Iterables such as generators can also feed into random selection upon conversion to lists:

# Generators: Saving memory, one number at a time! 🚀
gen = (x for x in range(10))  # Generator expression
random_gen_item = random.choice(list(gen))  # Converts generator to list, then selects.

No-replacement multiple random selections 🙅‍♀️

If you'd rather not allow selection repetition, use random.sample() in place of multiple random.choice() calls:

# Instead of this, which may repeat choices...🔁
repeated_choices = [random.choice(my_list) for _ in range(2)]

# Use this, to keep things fresh! 🍃
sampled_once = random.sample(my_list, 2)