Why Does Python's `random.shuffle()` Return `None` and How Can I Use It Correctly?

Shuffling a List of Objects

Problem:

Mistakes can occur when attempting to shuffle a list of objects using the random.shuffle() function. The expected shuffling behavior doesn't seem to occur, and the function outputs None instead.

Solution:

To effectively shuffle a list of objects, use the shuffle() function from the random module as follows:

from random import shuffle

objects = [obj1, obj2, obj3]  # initialize the list of objects
shuffle(objects)  # shuffle the objects in place

Explanation:

Unlike some other programming languages, in Python, random.shuffle() operates in place, meaning it modifies the original list without returning a new one. Additionally, it's common practice for functions in Python to return None when mutating objects is intended.

Sample Code:

from random import shuffle

x = [[i] for i in range(10)]
shuffle(x)
print(x)

This will shuffle the list of lists x and print the shuffled result.

Note:

It's important to remember that shuffle() alters the original list, so subsequent operations or accesses to the list will reflect the changes made by shuffle().

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