Shuffle a list, string, tuple in Python (random.shuffle, sample)

In Python, you can shuffle (i.e., randomize) a list with random.shuffle() and random.sample().

random.shuffle() shuffles a list in place, and random.sample() returns a new randomized list. random.sample() is also applicable to immutable data types, such as strings and tuples.

For information on sorting or reversing a list, refer to the following articles.

• Sort a list, string, tuple in Python (sort, sorted)
• Reverse a list, string, tuple in Python (reverse, reversed)

Shuffle a list in place: random.shuffle()

You can shuffle a list in place with random.shuffle().

• random.shuffle() — Generate pseudo-random numbers — Python 3.11.3 documentation

import random

l = [0, 1, 2, 3, 4]

random.shuffle(l)
print(l)
# [0, 3, 2, 4, 1]

Create a new shuffled list: random.sample()

random.sample() returns a new list with selected random elements from a list. The original list is not changed.

• Random sample from a list in Python (random.choice, sample, choices)

To create a new list with all elements randomly shuffled, set the total number of elements in the list as the second argument. You can find the total number of elements using len().

• Get the number of items of a list in Python

import random

l = [0, 1, 2, 3, 4]

l_shuffled = random.sample(l, len(l))
print(l_shuffled)
# [4, 3, 0, 1, 2]

print(l)
# [0, 1, 2, 3, 4]

Shuffle a string and tuple

Since strings and tuples are immutable, using random.shuffle() on them will result in a TypeError.

import random

s = 'abcde'

# random.shuffle(s)
# TypeError: 'str' object does not support item assignment

t = (0, 1, 2, 3, 4)

# random.shuffle(t)
# TypeError: 'tuple' object does not support item assignment

To shuffle a string or tuple, use random.sample(), which creates a new object.

Note that random.sample() returns a list, even when provided with a string or tuple. Thus, the resulting list must be converted back into the desired data type.

When used with a string, random.sample() returns a list of characters. To convert this back into a string, use the join() method.

• Concatenate strings in Python (+ operator, join, etc.)

s_shuffled = ''.join(random.sample(s, len(s)))
print(s_shuffled)
# aedcb

To convert a list back into a tuple, use tuple().

• Convert list and tuple to each other in Python

t_shuffled = tuple(random.sample(t, len(l)))
print(t_shuffled)
# (4, 1, 2, 0, 3)

The above examples demonstrate how to shuffle a string or tuple itself. If you want to deal with a list of strings or tuples, you can use random.sample() and random.shuffle() for shuffling.

l = ['apple', 'banana', 'cherry', 'date']

l_shuffled = random.sample(l, len(l))
print(l_shuffled)
# ['cherry', 'banana', 'apple', 'date']

random.shuffle(l)
print(l)
# ['date', 'apple', 'cherry', 'banana']

Fix the random seed: random.seed()

You can fix the random seed and initialize the random number generator with random.seed().

• random.seed() — Generate pseudo-random numbers — Python 3.11.3 documentation

Initializing with the same seed will produce the same shuffle pattern.

l = [0, 1, 2, 3, 4]
random.seed(0)
random.shuffle(l)
print(l)
# [2, 1, 0, 4, 3]

l = [0, 1, 2, 3, 4]
random.seed(0)
random.shuffle(l)
print(l)
# [2, 1, 0, 4, 3]