Python Program to Shuffle a List Using random.shuffle()

Use random.shuffle(your_list) to shuffle a list in Python in place, which rearranges the elements randomly.

Examples

Input[1, 2, 3]

Output[3, 1, 2]

Input["apple", "banana", "cherry"]

Output["banana", "cherry", "apple"]

Input[]

Output[]

How to Think About It

To shuffle a list, think of mixing cards in a deck so their order changes randomly. We want to rearrange the list elements without losing any, so each element moves to a new random position. Python's random.shuffle() does this by swapping elements randomly inside the list.

Algorithm

1

Import the random module.

2

Create or get the list you want to shuffle.

3

Call the shuffle function from the random module on the list.

4

The list is rearranged randomly in place.

5

Print or use the shuffled list.

Code

python

import random

my_list = [1, 2, 3, 4, 5]
random.shuffle(my_list)
print(my_list)

Output

[3, 1, 5, 2, 4]

Dry Run

Let's trace the list [1, 2, 3, 4, 5] through the shuffle code

1

Original list

my_list = [1, 2, 3, 4, 5]

2

Call random.shuffle

random.shuffle(my_list) rearranges elements randomly

3

Shuffled list

my_list might become [3, 1, 5, 2, 4]

4

Print result

print(my_list) outputs the shuffled list

Step	List State
Initial	[1, 2, 3, 4, 5]
After shuffle	[3, 1, 5, 2, 4]

Why This Works

Step 1: Import random module

The random module provides functions to generate random numbers and shuffle lists.

Step 2: Use random.shuffle()

random.shuffle() rearranges the list elements in place, meaning it changes the original list order randomly.

Step 3: Print the shuffled list

Printing the list shows the new random order after shuffling.

Alternative Approaches

Using random.sample() to create a new shuffled list

python

import random

my_list = [1, 2, 3, 4, 5]
shuffled_list = random.sample(my_list, len(my_list))
print(shuffled_list)

This creates a new shuffled list without changing the original list, but uses extra memory.

Manual shuffle using Fisher-Yates algorithm

python

import random

my_list = [1, 2, 3, 4, 5]
for i in range(len(my_list)-1, 0, -1):
    j = random.randint(0, i)
    my_list[i], my_list[j] = my_list[j], my_list[i]
print(my_list)

This manually implements the shuffle logic, useful for learning but more code than random.shuffle().

Complexity: O(n) time, O(1) space

Time Complexity

random.shuffle() runs in O(n) time because it swaps elements in the list once each, where n is the list length.

Space Complexity

It uses O(1) extra space since it shuffles the list in place without creating a new list.

Which Approach is Fastest?

random.shuffle() is fastest and most memory efficient compared to creating a new shuffled list with random.sample() which uses O(n) extra space.

Approach	Time	Space	Best For
random.shuffle()	O(n)	O(1)	In-place shuffling, memory efficient
random.sample()	O(n)	O(n)	Creating a new shuffled list without changing original
Manual Fisher-Yates	O(n)	O(1)	Learning shuffle algorithm, custom control