# Python – Replace sublist from Initial element

• Last Updated : 28 Jul, 2020

Given a list and replacement sublist, perform the replacement of list sublist on basis of initial element of replacement sublist.

Input : test_list = [3, 7, 5, 3], repl_list = [7, 8]
Output : [3, 7, 8, 3]
Explanation : Replacement starts at 7 hence 7 and 8 are replaced.

Input : test_list = [3, 7, 5, 3, 9, 10], repl_list = [5, 6, 7, 4]
Output : [3, 7, 5, 6, 7, 4]
Explanation : Replacement starts at 5 and goes till end of list.

Method : Using list comprehension + list slicing
The combination of above functionalities can be used to solve this problem. In this, we extract the index of beginning element, and then perform the appropriate slicing of list according to requirements.

 `# Python3 code to demonstrate working of ``# Replace substring from Initial element``# Using list slicing + list comprehension`` ` `# initializing list``test_list ``=` `[``5``, ``2``, ``6``, ``4``, ``7``, ``1``, ``3``]`` ` `# printing original list ``print``(``"The original list : "` `+` `str``(test_list))`` ` `# initializing repl_list ``repl_list ``=` `[``6``, ``10``, ``18``]`` ` `# Replace substring from Initial element``# Extracting index``idx ``=` `test_list.index(repl_list[``0``])`` ` `# Slicing till index, and then adding rest of list``res ``=` `test_list[ :idx] ``+` `repl_list ``+` `test_list[idx ``+` `len``(repl_list):]`` ` `# printing result ``print``(``"Substituted List : "` `+` `str``(res))`

Output :

```The original list : [5, 2, 6, 4, 7, 1, 3]
Substituted List : [5, 2, 6, 10, 18, 1, 3]
```

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