Python – All replacement combination from other list

Last Updated : 10 Mar, 2023

Given a list, the task is to write a Python program to perform all possible replacements from other lists to the current list.

Input : test_list = [4, 1, 5], repl_list = [8, 10]
Output : [(4, 1, 5), (4, 1, 8), (4, 1, 10), (4, 5, 8), (4, 5, 10), (4, 8, 10), (1, 5, 8), (1, 5, 10), (1, 8, 10), (5, 8, 10)]
Explanation : All elements are replaced by 0 or more elements from 2nd list

Input : test_list = [4, 1], repl_list = [8, 10]
Output : [(4, 1), (4, 8), (4, 10), (1, 8), (1, 10), (8, 10)]
Explanation : All elements are replaced by 0 or more elements from 2nd list

Method #1 : Using combinations() + len()

In this, we perform the task of constructing combinations of the merged lists using combinations() and len() is used to restrict the size of output to the length of the initial list.

Python3

# Python3 code to demonstrate working of
# All replacement combination from other list
# Using combinations() + len()
from itertools import combinations
 
# initializing list
test_list = [4, 1, 5]
 
# printing original list
print("The original list is : " + str(test_list))
 
# initializing replacement list
repl_list = [8, 10]
 
# using combinations() to get all combinations replacements
res = list(combinations(test_list + repl_list, len(test_list)))
 
# printing result
print("All combinations replacements from other list : " + str(res))

Output:

The original list is : [4, 1, 5] All combinations replacements from other list : [(4, 1, 5), (4, 1, 8), (4, 1, 10), (4, 5, 8), (4, 5, 10), (4, 8, 10), (1, 5, 8), (1, 5, 10), (1, 8, 10), (5, 8, 10)]

Time Complexity: O(n)
Auxiliary Space: O(1)

Method #2 : Using combinations() + extend()

In this, we perform the task of concatenating the list using extend(), rest all the functionalities is similar to the above method.

Python3

# Python3 code to demonstrate working of 
# All replacement combination from other list
# Using combinations() + extend()
from itertools import combinations
 
# initializing list
test_list = [4, 1, 5]
 
# printing original list
print("The original list is : " + str(test_list))
 
# initializing replacement list 
repl_list = [8, 10]
 
# using combinations() to get all combinations replacements
# extend() for concatenation
n = len(test_list)
test_list.extend(repl_list)
res = list(combinations(test_list, n))
 
# printing result 
print("All combinations replacements from other list : " + str(res))

Output:

The original list is : [4, 1, 5] All combinations replacements from other list : [(4, 1, 5), (4, 1, 8), (4, 1, 10), (4, 5, 8), (4, 5, 10), (4, 8, 10), (1, 5, 8), (1, 5, 10), (1, 8, 10), (5, 8, 10)]

Time Complexity: O(n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(n), where n is the number of elements in the list “test_list”.