# Python – Replace String by Kth Dictionary value

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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