HackerRank Python Solution - Strings - Mutations

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

Sample Input:

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

Sample Output:

abrackdabra

Solution:

def mutate_string(string, position, character):
    
    string_list = list(string)
    string_list[position]=character
    return ''.join(string_list)

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

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