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# Python Program to replace elements of a list based on the comparison with a number

• Last Updated : 10 Mar, 2023

Given a list, the task here is to write a Python program to replace its elements after comparing them with another number here described using K.

For the example depicted in this article, any number greater than K will be replaced with the value given in high and any number less than or equal to K will be replaced with the value given in low.

Input : test_list = [7, 4, 3, 2, 6, 8, 9, 1], low = 2, high = 9, K = 5

Output : [9, 2, 2, 2, 9, 9, 9, 2]

Explanation : Elements less than K substituted by 2, rest are by 9.

Input : test_list = [7, 4, 3, 2, 6, 8, 9, 1], low =2, high = 8, K = 5

Output : [8, 2, 2, 2, 8, 8, 8, 2]

Explanation : Elements less than K substituted by 2, rest are by 8.

Method 1 : Using loop

In this, we perform replacements using conditional statements and iteration is performed using loop.

Program:

## Python3

 `# initializing list``test_list ``=` `[``7``, ``4``, ``3``, ``2``, ``6``, ``8``, ``9``, ``1``]` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))` `# initializing K``K ``=` `5` `# initializing low and high Replacement Replacement``low, high ``=` `2``, ``9` `res ``=` `[]``for` `ele ``in` `test_list:` `    ``# conditional tests``    ``if` `ele > K:``        ``res.append(high)``    ``else``:``        ``res.append(low)` `# printing result``print``(``"List after replacement ? : "` `+` `str``(res))`

Output:

The original list is : [7, 4, 3, 2, 6, 8, 9, 1]

List after replacement ? : [9, 2, 2, 2, 9, 9, 9, 2]

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

Method 2 : Using list comprehension

Similar to the method above, only difference is this is a one liner solution and a compact alternative using list comprehension.

Program:

## Python3

 `# initializing list``test_list ``=` `[``7``, ``4``, ``3``, ``2``, ``6``, ``8``, ``9``, ``1``]` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))` `# initializing K``K ``=` `5` `# initializing low and high Replacement Replacement``low, high ``=` `2``, ``9` `# list comprehension for shorthand solution``res ``=` `[high ``if` `ele > K ``else` `low ``for` `ele ``in` `test_list]` `# printing result``print``(``"List after replacement ? : "` `+` `str``(res))`

Output:

The original list is : [7, 4, 3, 2, 6, 8, 9, 1]

List after replacement ? : [9, 2, 2, 2, 9, 9, 9, 2]

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”.

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