2 posts tagged “algorithm”

Rewritten to make it more modular, basically works the same way as before.

import sys

alphabet = 'abcdefghijklmnopqrstuvwxyz'
balphabet = 'zyxwvutsrqponmlkjihgfedcba'

class LetterBack:
    '''Class for Encrypting a string of letters'''
   
    def __init__(self, text='mnm'):
        self.text = text
       
    def encrypt(self, aSentance):
        '''Encrypts a given string by replacing each letter
        with the letter before it in the alphabet.'''
        output = ''
        for element in aSentance:
            for i in range(26):
                if element == alphabet[i]:
                    output += alphabet[i-1]
        print output

    def decrypt(self, aSentance):
        '''Decrypts a given string encoded by the encrypt
         function.'''
        output = ''
        for element in aSentance:
            #print element + ' this is 1'
            for i in range(26):
                if element == balphabet[i]:
                    output += balphabet[i-1]
        print output

def main():
    lb = LetterBack()
    if sys.argv[1] == '-e':
        lb.encrypt(sys.argv[2])
    elif sys.argv[1] == '-d':
        lb.decrypt(sys.argv[2])

if __name__ == '__main__':
    main()

use:
python letterback.py -e 'alvin'
returns: zkuhm
python letterback.py -d 'zkuhm'
returns: alvin

or in the python interpreter:
>>> from letterback import LetterBack
>>> lb = LetterBack()
>>>lb.encrypt('alvin')
zkuhm
>>> lb.decrypt('zkuhm')
alvin

enjoy :)

I scripted this up really quick last night while my girlfriend and I were having fun sending cryptic messages to each other. Basically all it does is encode or decode a string of letters given as CLI arguments. The program takes a given string and prints out in place of each letter a letter before that letter in the alphabet. For example: a = z, b = a, and so on....

Here is a code:


#! /usr/bin/python
#
# Author: Alvin D. Morris
# Date: August 5, 2008
#
# Program for encrypting a string of text.

import sys

alphabet = 'abcdefghijklmnopqrstuvwxyz'
balphabet = 'zyxwvutsrqponmlkjihgfedcba'

def encrypt(aSentance):
    '''Encrypts a given string by replacing each letter with the letter before it in the alphabet.'''
    output = ''
    for element in aSentance:
        for i in range(26):
            if element == alphabet[i]:
                output += alphabet[i-1]
    print output

def decrypt(aSentance):
    '''Decrypts a given string encoded by the encrypt function.'''
    output = ''
    for element in aSentance:
        #print element + ' this is 1'
        for i in range(26):
            if element == balphabet[i]:
                output = output + balphabet[i-1]
    print output

def main():
    if sys.argv[1] == '-e':
        encrypt(sys.argv[2])
    elif sys.argv[1] == '-d':
        decrypt(sys.argv[2])

if __name__ == '__main__':
    main()


Usage:
python back.py -e alvin
returns:  zkuhm
python back.py -d zkuhm
returns: alvin