Print all sublists of a list in Python

Given a list, print all the sublists of a list. Python provides efficient and elegant ways to generate and manipulate sublists. In this article, we will explore different methods how to print all sublists of a given list.

Examples:

Input: list = [1, 2, 3] 
Output: [[], [1], [1, 2], [1, 2, 3], [2], [2, 3], [3]]
Input: [1, 2, 3, 4] 
Output: [[], [1], [1, 2], [1, 2, 3], [1, 2, 3, 4], [2], [2, 3], [2, 3, 4], [3], [3, 4], [4]]
Explanation: In This, we are printing all sublists of a list in Python.

Python program to print all sublists of a list

There are multiple approaches to generating sublists in Python. Let’s explore a few methods and their corresponding code snippets:

• Using Nested Loops
• Using List Comprehension
• Using Iterative Approach
• Using Recursion

Get all possible sublists of a list using Nested Loops

To generate and print all sublists of a list using nested loops, you need to iterate through the list with two loops: an outer loop and an inner loop. The outer loop sets the starting index of the sublist, while the inner loop determines the ending index. By controlling these indices, you can extract and print all the possible sublists.

Python3

def sublists(lst):
    n = len(lst)
    sublists = []

    for start in range(n):
        for end in range(start + 1, n + 1):
            sublists.append(lst[start:end])

    return sublists

original_list = [1, 2, 3]
sublists_nested = sublists(original_list)
print(sublists_nested)

Output:

[[1], [1, 2], [1, 2, 3], [2], [2, 3], [3]]

Get all possible sublists of a list using List Comprehension

Using list comprehension to create sublists of a list is a clear and effective technique. You can create new lists using list comprehension by defining a short expression that iteratively evaluates each item in the list. List comprehension can effectively achieve the required result when used to create sublists.

Python3

def sublists(lst):
    return [lst[i:j] for i in range(len(lst)) for j in range(i + 1, len(lst) + 1)]

original_list = [9,8,7]
sublists_list = sublists(original_list)
print(sublists_list)

Output:

[[9], [9, 8], [9, 8, 7], [8], [8, 7], [7]]

Get all possible sublists of a list using Iterative Method

In this, we uses an iterative approach to print all possible sublists of a given list. It iterates through the list, using two nested loops to determine the starting and ending indices of each sublist. The sublists are then printed one by one. Below is the Python implementation of the above approach:

Python

# function to generate all the sub lists
def sublists(lst):
    sublists_list = []
    for i in range(len(lst)):
        for j in range(i + 1, len(lst) + 1):
            sublists_list.append(lst[i:j])
    return sublists_list

original_list = [2,3,4,9]
sublists_list = sublists(original_list)
print(sublists_list)

Output:

[[2], [2, 3], [2, 3, 4], [2, 3, 4, 9], [3], [3, 4], [3, 4, 9], [4], [4, 9], [9]]

Time Complexity: O(n*n)
Auxiliary Space: O(n)

Generate all sublists of a list using Recursion

In this, we defines a recursive function generate_sublists that generates all sublists of a given list by including or excluding the first element. It builds sublists by recursively generating sublists for the rest of the elements and combining them with the first element. The result is a list containing all possible sublists of the input list.

Python3

def sublists(lst, index=0, current=[]):
    if index == len(lst):
        print(current)
        return
    sublists(lst, index+1, current)
    sublists(lst, index+1, current + [lst[index]])

lst = [1, 2, 3]
sublists(lst)

Output:

[]
[3]
[2]
[2, 3]
[1]
[1, 3]
[1, 2]
[1, 2, 3]