# dev@brattham.se (2020-06-02) v1.0 # License: GPLv3 (see: https://www.gnu.org/licenses/gpl-3.0.html) """Input a message to coding/decoding it. ROT13 is a letter substitution cipher for coding/decoding a inputed text message. """ # input string to cipher/decipher s = input("Input text to encipher/decipher: ") print(s) # communicate input to user # put characters s in a list l l = list(s) # char elements in l # offset for characters to encipher ofst = 13 # "rot13" # loop through the characters c in l for c in range(len(l)): # find c in l to cipher/decipher if ( "A" <= l[c] <= "M" or "a" <= l[c] <= "m" ): l[c] = chr(ord(l[c]) + ofst) elif ( "N" <= l[c] <= "Z" or "n" <= l[c] <= "z" ): l[c] = chr(ord(l[c]) - ofst) # convert list l to a new string rt13 rt13 = "".join(l) print(f"\nrot13: {s} -> {rt13}") # ----------------------------------- # I n f o (about the project) # ----------------------------------- # project name: rot13 # project type: easy cipher # creator: Per Bratthammar, Sweden # project start: 2020-06-02 (v0.1) # release v1.0: 2020-06-02 # Program languages: Python 3 # project: rot13 # ----------------------------------- # About rot13: # - purpose: easy cipher on kid level for fun and easy to code and understand # - how to: input text to cipher with rot13. Deciffer to in put the in the ciphered text again, and text come back. # - the cipher is build on an idea that english alphabet is 26 characters and when cipher, the charaters is rotating 13 positions (half the alphabet). # ----------------------------------- # comments: # -> developed and tested on Sololearns iPhone app. # -> easy level # you can even use list comprehension: # # rt13 = [chr(ord(c) + 13) if 'A'<= c <= 'M' or 'a' <= c <= 'm' else chr(ord(c) - 13) if 'A'<= c <= 'Z' or 'a' <= c <= 'z' else c for c in s] # # where the number 13 can be derived to: # round((ord('Z') - ord('A') + 1) / 2) # # ----------------------------------- # release log: - #

<py> ROT13 (v1.0)