freecodecamp--freecodecamp/curriculum/challenges/english/blocks/daily-coding-challenges-python/68216ef80f957572e7c340c5.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
68216ef80f957572e7c340c5	Challenge 12: Message Decoder	29	challenge-12

--description--

Given a secret message string, and an integer representing the number of letters that were used to shift the message to encode it, return the decoded string.

• A positive number means the message was shifted forward in the alphabet.
• A negative number means the message was shifted backward in the alphabet.
• Case matters, decoded characters should retain the case of their encoded counterparts.
• Non-alphabetical characters should not get decoded.

--hints--

decode("Xlmw mw e wigvix qiwweki.", 4) should return "This is a secret message."

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(decode("Xlmw mw e wigvix qiwweki.", 4), "This is a secret message.")`)
}})

decode("Byffi Qilfx!", 20) should return "Hello World!"

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(decode("Byffi Qilfx!", 20), "Hello World!")`)
}})

decode("Zqd xnt njzx?", -1) should return "Are you okay?"

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(decode("Zqd xnt njzx?", -1), "Are you okay?")`)
}})

decode("oannLxmnLjvy", 9) should return "freeCodeCamp"

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(decode("oannLxmnLjvy", 9), "freeCodeCamp")`)
}})

--seed--

--seed-contents--

def decode(message, shift):

    return message

--solutions--

def decode(message, shift):
    decoded_message = []
    for char in message:
        if char.isalpha():
            base = ord('a') if char.islower() else ord('A')
            new_char = chr((ord(char) - base - shift) % 26 + base)
            decoded_message.append(new_char)
        else:
            decoded_message.append(char)
    return ''.join(decoded_message)