How Can I Generate All Permutations of a List in Python?

Generating All Permutations of a List

Given a list of elements, the task is to generate all possible permutations of the elements. Permutations are different combinations of the elements in the list.

Standard Library Solution

The Python standard library provides the itertools.permutations function for this purpose:

import itertools
list(itertools.permutations([1, 2, 3]))

This code generates all the permutations of the list [1, 2, 3] and returns them as a list of tuples.

Alternative Implementations

Here is an alternative implementation of a permutations function using recursion:

def permutations(elements):
    if len(elements) <= 1:
        yield elements
        return
    for perm in permutations(elements[1:]):
        for i in range(len(elements)):
            yield perm[:i] + elements[0:1] + perm[i:]

This implementation constructs permutations by iteratively adding the first element of the list to different positions in the permutations of the remaining elements.

Another alternative approach uses itertools.product:

def permutations(iterable, r=None):
    pool = tuple(iterable)
    n = len(pool)
    r = n if r is None else r
    for indices in product(range(n), repeat=r):
        if len(set(indices)) == r:
            yield tuple(pool[i] for i in indices)

This implementation iterates over all possible combinations of indices from 0 to n-1 (where n is the list length) and generates a permutation from each combination if the indices are unique (indicating that each element in the list is included once).

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