Secret Message

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Note: This page contains a small but interesting piece of Python code which I call snippets. You can find more such codes on my Python snippets page.

Contents

  1. Problem
  2. Solution
  3. Explanation

Problem

You are trying to send a secret message, and you've decided to encode it by replacing every letter in your message with its corresponding letter in a backwards version of the alphabet. What do your messages look like?

Task:
Create a program that replaces each letter in a message with its corresponding letter in a backwards version of the English alphabet.

Input Format:
A string of your message in its normal form.

Output Format:
A string of your message once you have encoded it (all lower case).

Sample Input:
Hello World

Sample Output:
svool dliow

Solution

Here is my solution to the above problem. Remember that there could be more than one way to solve a problem. If you have a more efficient or concise solution, please leave a comment.

In [1]:
import string
az=string.ascii_lowercase
print("".join([az[-az.index(x)-1] if x in az else x for x in input().lower()]))

svool dliow!

Explanation

My approach (or the algorithm)

  1. Convert the input to lowercase.
  2. Create a list of lowercase letters from a to z.
  3. Find the position of each letter of the input string in the alphabet list.
  4. Find a corresponding letter in the alphabet list with the same position from the end of the list.
  5. Replace each letter from input string with the corresponding letter found in the alphabet llst.

The code

  • input().lower() converts input to lowercase.
  • if x in az we will make changes only if the letter is an alphabet and not a number or a special character.
  • az.index(x) gives the position of the input letter in the alphabet list.
  • -az.index(x)-1 gives the position of the letter in the alphabet list from the end.
  • [az[-az.index(x)-1] if x in az else x for x in input().lower()] replace all letters using list comprehension.
  • "".join() join into a string.

The problem question is picked from SoloLearn. Here is my SoloLearn code and my SoloLearn profile page.

Last updated 2021-01-09 18:18:58.213994 IST

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