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Python – Replace String by Kth Dictionary value
• Last Updated : 01 Aug, 2020

Given list of Strings, replace the value mapped by Kth value of mapped list.

Input : test_list = [“Gfg”, “is”, “Best”], subs_dict = {“Gfg” : [5, 6, 7], “is” : [7, 4, 2]}, K = 0
Output : [5, 7, “Best”]
Explanation : “Gfg” and “is” is replaced by 5, 7 as 0th index in dictionary value list.

Input : test_list = [“Gfg”, “is”, “Best”], subs_dict = {“Gfg” : [5, 6, 7], “Best” : [7, 4, 2]}, K = 0
Output : [5, “is”, 7]
Explanation : “Gfg” and “Best” is replaced by 5, 7 as 0th index in dictionary value list.

Method #1 : Using list comprehension

This is one of the ways in which this task can be performed. In this, we perform the task iteration and conditional replacement inside one-liner in list comprehension.

## Python3

 `# Python3 code to demonstrate working of ``# Replace String by Kth Dictionary value  ``# Using list comprehension`` ` `# initializing list``test_list ``=` `[``"Gfg"``, ``"is"``, ``"Best"``]`` ` `# printing original list``print``(``"The original list : "` `+` `str``(test_list))`` ` `# initializing subs. Dictionary``subs_dict ``=` `{``    ``"Gfg"` `: [``5``, ``6``, ``7``], ``    ``"is"` `: [``7``, ``4``, ``2``], ``}`` ` `# initializing K ``K ``=` `2`` ` `# using list comprehension to solve``# problem using one liner``res ``=` `[ele ``if` `ele ``not` `in` `subs_dict ``else` `subs_dict[ele][K]``                                     ``for` `ele ``in` `test_list]``         ` `# printing result ``print``(``"The list after substitution : "` `+` `str``(res))`
Output
```The original list : ['Gfg', 'is', 'Best']
The list after substitution : [7, 2, 'Best']
```

Method #2 : Using get() + list comprehension

The combination of above functions can be used to solve this problem. In this, we iterate using list comprehension and check for key existence and substitution using get().

## Python3

 `# Python3 code to demonstrate working of ``# Replace String by Kth Dictionary value  ``# Using get() + list comprehension`` ` `# initializing list``test_list ``=` `[``"Gfg"``, ``"is"``, ``"Best"``]`` ` `# printing original list``print``(``"The original list : "` `+` `str``(test_list))`` ` `# initializing subs. Dictionary``subs_dict ``=` `{``    ``"Gfg"` `: [``5``, ``6``, ``7``], ``    ``"is"` `: [``7``, ``4``, ``2``], ``}`` ` `# initializing K ``K ``=` `2`` ` `# using list comprehension to solve problem using one liner``# get() to perform presence checks and assign default value``res ``=` `[subs_dict.get(ele, ele) ``for` `ele ``in` `test_list]``res ``=` `[ele[K] ``if` `isinstance``(ele, ``list``) ``else` `ele ``for` `ele ``in` `res] ``         ` `# printing result ``print``(``"The list after substitution : "` `+` `str``(res))`
Output
```The original list : ['Gfg', 'is', 'Best']
The list after substitution : [7, 2, 'Best']
```

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