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Python itertools.permutations() Function

The Python itertools.permutations() function is used to generate all possible ordered arrangements (permutations) of elements from a given iterable. It allows you to specify the length of each permutation.

This function is useful in combinatorial problems where order matters, such as password generation, game mechanics, and arrangement problems.

Following is the syntax of the Python itertools.permutations() function −

itertools.permutations(iterable, r=None)

This function accepts the following parameters −

• iterable: The input iterable whose elements will be arranged in different orders.
• r (optional): The length of each permutation. If not specified, it defaults to the length of the iterable.

This function returns an iterator that produces tuples representing all possible permutations.

Following is an example of the Python itertools.permutations() function. Here, we generate all possible orderings of a list of numbers −

import itertools

numbers = [1, 2, 3]

result = itertools.permutations(numbers)
for item in result:
   print(item)

Following is the output of the above code −

(1, 2, 3)
(1, 3, 2)
(2, 1, 3)
(2, 3, 1)
(3, 1, 2)
(3, 2, 1)

Here, we specify a permutation length of 2, generating pairs of elements from the given set −

import itertools

letters = ['A', 'B', 'C']

result = itertools.permutations(letters, 2)
for item in result:
   print(item)

Output of the above code is as follows −

('A', 'B')
('A', 'C')
('B', 'A')
('B', 'C')
('C', 'A')
('C', 'B')

Now, we use itertools.permutations() function to generate all possible orders of characters in a string −

import itertools

word = "DOG"

result = itertools.permutations(word)
for item in result:
   print(''.join(item))

The result obtained is as shown below −

DOG
DGO
ODG
OGD
GDO
GOD

When working with passwords or combination locks, the itertools.permutations() function can help generate all possible sequences −

import itertools

digits = ['1', '2', '3']

result = itertools.permutations(digits, 3)
for combination in result:
   print(''.join(combination))

The result produced is as follows −

123
132
213
231
312
321

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