Python Specific Range Addition in List (original) (raw)

Last Updated : 25 Apr, 2025

Sometimes, while working with Python, we need to perform an edition in the Python list. And sometimes we need to perform this to a specific index range in it. This kind of application can have applications in many domains. Let us discuss certain ways in which this task can be performed.

Method #1: Using loop

This is a brute way in which this task can be performed. In this, we just iterate through the specified range in which the edition has to be performed.

Python3

test_list = [ 4 , 5 , 6 , 8 , 10 , 11 ]

print ( "The original list is : " + str (test_list))

i, j = 2 , 5

for idx in range (i, j):

`` test_list[idx] + = 3

print ( "List after range addition : " + str (test_list))

Output :

The original list is : [4, 5, 6, 8, 10, 11] List after range addition : [4, 5, 9, 11, 13, 11]

Time Complexity: O(n) where n is the number of elements in the list “test_list”.
Auxiliary Space: O(1), constant extra space is needed

Method #2: Using list comprehension

This task can also be performed using list comprehension. This method uses the same way as above but it’s a shorthand for the above.

Python3

test_list = [ 4 , 5 , 6 , 8 , 10 , 11 ]

print ( "The original list is : " + str (test_list))

i, j = 2 , 5

test_list[i: j] = [ele + 3 for ele in test_list[i: j]]

print ( "List after range addition : " + str (test_list))

Output :

The original list is : [4, 5, 6, 8, 10, 11] List after range addition : [4, 5, 9, 11, 13, 11]

Method #3: Using numpy Here is one approach using numpy library:

Note: Install numpy module using command “pip install numpy”

Python3

import numpy as np

test_list = [ 4 , 5 , 6 , 8 , 10 , 11 ]

print ( "The original list is : " + str (test_list))

i, j = 2 , 5

test_list = np.array(test_list)

test_list[i:j] + = 3

print ( "List after range addition : " + str (test_list.tolist()))

Output:

The original list is : [4, 5, 6, 8, 10, 11] List after range addition : [4, 5, 9, 11, 13, 11]

Time Complexity: O(n), where n is the length of the list.
Auxiliary Space: O(n), as a numpy array of the same length as the list is created.

Explanation:

• Import the numpy library
• Convert the list to a numpy array
• Add 3 to the specific range (i:j) of the numpy array
• Convert the numpy array back to a list and print the result.

Method 4: Using the slice notation and the built-in map function.

Python3

test_list = [ 4 , 5 , 6 , 8 , 10 , 11 ]

i, j = 2 , 5

test_list[i:j] = map ( lambda x: x + 3 , test_list[i:j])

print ( "List after range addition : " + str (test_list))

Output

List after range addition : [4, 5, 9, 11, 13, 11]

Time complexity of O(n), where n is the length of the list.
Auxiliary space: O(1), as we’re only modifying the original list and not creating any additional data structures.