Mutations in Python - HackerRank Solution

Problem

We have seen that lists are mutable (they can be changed), and tuples are immutable (they cannot be changed).

Let's try to understand this with an example.
You are given an immutable string, and you want to make changes to it.

Example
>>> string = "abracadabra"

You can access an index by:
>>> print string[5]
a

What if you would like to assign a value?
>>> string[5] = 'k' 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment


How would you approach this?
One solution is to convert the string to a list and then change the value.

Example
>>> string = "abracadabra"
>>> l = list(string)
>>> l[5] = 'k'
>>> string = ''.join(l)
>>> print string
abrackdabra

Another approach is to slice the string and join it back.
Example
>>> string = string[:5] + "k" + string[6:]
>>> print string
abrackdabra


Task

Read a given string, change the character at a given index and then print the modified string.


Function Description

Complete the mutate_string function in the editor below.

mutate_string has the following parameters:
  • string string: the string to change
  • int position: the index to insert the character at
  • string character: the character to insert


Returns

string: the altered string


Input Format

The first line contains a string, .
The next line contains an integer , the index location and a string , separated by a space.


Sample Input

STDIN           Function
-----           --------
abracadabra     s = 'abracadabra'
5 k             position = 5, character = 'k'


Sample Output

abrackdabra


Program

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def mutate_string(string, position, character):
    pos = position+1
    result = string[:position]+character+string[(pos):]
    return result

if __name__ == '__main__':
    s = input()
    i, c = input().split()
    s_new = mutate_string(s, int(i), c)
    print(s_new)
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