Python coding/ decoding cipher

Question

I am trying to encode and then decode this function in python using cipher encryption. I wrote this function. how do I change this function so that it encodes both lower and uppercase letters?

def encrypt(message, key):
  alphabet="abcdefghijklmnopqrstuvwxyz"
  encMessage=""

  for character in message:
      if character in alphabet:
          index = alphabet.find(character)
          newPosition = (index+key)%26
          newCharacter = alphabet[newPosition]
          encMessage+=newCharacter
      else:
          encMessage+=character

  return encMessage

Use `character.lower()` to get the lowercase version of the letter — Barmar, Feb 10 '18 at 01:26
`(index+key)%26` is not guaranteed to be an alphanumeric character , by the way — OneCricketeer, Feb 10 '18 at 01:33
How can it be above the for loop? The `character` variable isn't defined there. — Barmar, Feb 10 '18 at 02:01
But you could also just do `message = message.lower()` before the loop. — Barmar, Feb 10 '18 at 02:01
Did you really write this function? It's exactly the same as [this question](https://stackoverflow.com/questions/48716794/python-encoding-decoding-using-caesar-cipher) — Barmar, Feb 10 '18 at 03:08

Olivier Melançon · Answer 1 · 2018-02-10T04:04:15.890

0

You can extend the alphabet with uppercase letters. You will also need to update the modulo operation to get your newPosition.

def encrypt(message, key):

  # Extend your alphabet
  alphabet="abcdefghijklmnopqrstuvwxyz"
  alphabet += alphabet.upper()

  encMessage=""

  for character in message:
      if character in alphabet:
          index = alphabet.find(character)

          # Use the correct modulo
          newPosition = (index+key) % len(alphabet)

          newCharacter = alphabet[newPosition]
          encMessage+=newCharacter
      else:
          encMessage+=character

  return encMessage

edited Feb 10 '18 at 04:04

answered Feb 10 '18 at 03:48

Olivier Melançon

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Did you miss the comment in the other question where he admitted that he has multiple SO accounts and he wrote both questions? – Barmar Feb 10 '18 at 04:02
I did not, should I remove the notice? What do you recommend, you seem to be more aware of what is going on. – Olivier Melançon Feb 10 '18 at 04:03
1

Just remove the notice – Barmar Feb 10 '18 at 04:04
Done, thanks for your work to figure out what was going on here. – Olivier Melançon Feb 10 '18 at 04:05

Python coding/ decoding cipher

1 Answers1