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# Python | Insert a value after every k letters in a given list of strings

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As we know, inserting an item into a list is quite common, but sometimes we need to work with a list of strings, looking at each letter and inserting some repetitive items at a fixed frequency. Let’s see how to solve this problem with Python.

Method # 1: Using the enumerate () method

 ` # Python program to insert value after ` ` # every k letters in the given list of strings ` ` list1 ` ` = ` ` [` `’ p’ ` `, ` ` ’y’ ` `, ` `’ t’ ` `, ` ` ’h’ ` `, ` `’ o’ ` `, ` ` ’n’ ` `] `   ` # print original list ` ` print ` ` (` ` "Original list:" ` ` + ` ` str ` ` (list1)) `   ` # initialization to ` ` k ` ` = ` `’ G’ `   ` # initialization N ` ` N ` ` = ` ` 2 `   ` # using join () + enumerate () ` ` # insert K after every Nth number ` ` output ` ` = ` ` list ` ` (’’ .join (i ` ` + ` ` k ` ` * ` < code class = "plain"> (N `% ` ` 2 ` ` = ` ` = ` ` 1 ` `) ` ` for ` ` N, i ` ` in ` ` enumerate ` ` (list1))) `   ` # print result ` ` print ` ` ( ` ` "The lists after insertion:" ` ` + ` ` str ` ` (output)) `

Output:

` Original list: [’p’,’ y’, ’t’,’ h’, ’o’,’ n’] The lists after insertion: [’p’,’ y’, ’G’,’ t’, ’h’,’ G’, ’o’,’ n’, ’G’] `

Method # 2: Used no itertools

 ` # Python program to insert value after ` ` # every k letters in the given list lines ` ` from ` ` itertools ` ` import ` ` chain `   ` list1 ` ` = ` ` [` ` ’p’ ` `, ` `’ y’ ` `, ` ` ’t’ ` `, ` ` ’h’ ` `, ` ` ’o’ ` `, ` `’ n’ ` `] `   ` # print the original list ` ` print ` ` (` ` "Original list:" ` ` + ` ` str ` ` (list1)) `   ` # initialize to ` ` k ` ` = ` ` ’x’ `   ` # initialization N ` ` N ` ` = ` ` 3 `     ` # insert K after every Nth number ` ` output ` ` = ` ` list ` ` (chain (` ` * ` ` [list1 [i: i ` ` + ` ` N] ` ` + ` ` [k] ` ` if ` ` len ` ` (list1 [i: i ` ` + ` ` N]) ` ` = ` ` = ` ` N ` ` else ` ` list1 [i: i ` ` + ` ` N] ` ` ` ` for ` ` i ` ` in ` ` range ` ` (` ` 0 ` `, ` ` len ` ` (list1), N)])) `   ` # print result ` ` print ` ` (` ` "The lists after insertion:" ` ` + ` ` str ` ` (output)) `

Exit:

` Original list: [’p’,’ y’, ’t’,’ h’, ’o’,’ n’] The lists after insertion: [’p’,’ y’, ’t’,’ x’, ’h’ , ’o’,’ n’, ’x’] `