# Python Program to replace list elements within a range with a given number

• Last Updated : 24 Jan, 2021

Given a range, the task here  is to write a python program that can update the list elements falling under a given index range with a specified number.

Input : test_list = [4, 6, 8, 1, 2, 9, 0, 10, 12, 3, 9, 1], i, j = 4, 8, K = 9

Output : [4, 6, 8, 1, 9, 9, 9, 9, 12, 3, 9, 1]

Explanation : List is updated with 9 from 4th to 8th index.

Input : test_list = [4, 6, 8, 1, 2, 9, 0, 10, 12, 3, 9, 1], i, j = 4, 8, K = 8

Output : [4, 6, 8, 1, 8, 8, 8, 8, 12, 3, 9, 1]

Explanation : List is updated with 8 from 4th to 8th index.

Method 1 : Using slicing and * operator

In this, we perform task of getting elements of range using slicing and * operator is used to perform update and provide required elements to fill updates.

Program:

## Python3

 `# initializing list``test_list ``=` `[``4``, ``6``, ``8``, ``1``, ``2``, ``9``, ``0``, ``10``, ``12``, ``3``, ``9``, ``1``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing i, j``i, j ``=` `4``, ``8`` ` `# initializing K``K ``=` `9`` ` `# getting range using slicing and``# required elements using * operator``test_list[i:j] ``=` `[K] ``*` `(j ``-` `i)`` ` `# printing result``print``(``"Range Updated list : "` `+` `str``(test_list))`

Output:

The original list is : [4, 6, 8, 1, 2, 9, 0, 10, 12, 3, 9, 1]

Range Updated list : [4, 6, 8, 1, 2, 9, 0, 10, 12, 3, 9, 1, 9]

Method 2 : Using repeat() and list slicing

The similar task can also be performed using repeat(), which uses unbuilt constructs to get required elements.

Program:

## Python3

 `from` `itertools ``import` `repeat`` ` `# initializing list``test_list ``=` `[``4``, ``6``, ``8``, ``1``, ``2``, ``9``, ``0``, ``10``, ``12``, ``3``, ``9``, ``1``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing i, j``i, j ``=` `4``, ``8`` ` `# initializing K``K ``=` `9`` ` `# getting range using slicing and``# required elements using repeat()``test_list[i:j] ``=` `repeat(K, (j ``-` `i))`` ` `# printing result``print``(``"Range Updated list : "` `+` `str``(test_list))`

Output:

The original list is : [4, 6, 8, 1, 2, 9, 0, 10, 12, 3, 9, 1]

Range Updated list : [4, 6, 8, 1, 2, 9, 0, 10, 12, 3, 9, 1, 9]

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