How to Get All Combinations of a List in Python

09/08/2021

Contents

In this article, you will learn how to get all combinations of a list in Python.

Get All Combinations of a List

There are several ways to get all combinations of a list in Python. Here are two common methods:

Using the itertools module

The itertools module in Python provides a function called combinations that takes two arguments: an iterable objects and an integer n, and returns an iterator over n-length tuples of elements from the input iterable. To get all combinations, you can use a for loop and generate all combinations for each length starting from 1 to the length of the list.

import itertools

def all_combinations(lst):
    result = []
    for i in range(1, len(lst)+1):
        combinations = list(itertools.combinations(lst, i))
        result.extend(combinations)
    return result

Using Recursion

Another way to get all combinations of a list is to use recursion. The basic idea is to generate all combinations for a sublist, and then add each element in the list to the sublist one by one.

def all_combinations(lst):
    if len(lst) == 0:
        return [[]]
    result = []
    for i in range(len(lst)):
        m = lst[i]
        rem_list = lst[:i] + lst[i+1:]
        for p in all_combinations(rem_list):
            result.append([m] + p)
    return result

Both of these methods return a list of tuples, where each tuple represents a combination of elements from the original list.

#Python