Cypher.py

#!/usr/bin/env python3
# # -*- coding: utf-8 -*-
# cypher.py is a simple script that allows
# for user input and gives a choice of shifting
# the symbols for encryption and/or decryption.

__file_name__ = 'cipher.py'
__author__ = 'Dan Evans'
__copyright__ = 'Copyright 2017©, Coding With Py'
__credits__ = 'Dan Evans'
__dct_url__ = 'http://purl.org/dc/terms/'
__license__ = 'Creative Commons'
__rel_url__ = 'http://creativecommons.org/licenses/by-nc/4.0/'
__version__ = 'CC-by-nc/4.0/'
__maintainer__ = 'Dan(Python253)Evans'
__email__ = 'Python253@gmail.com'

print('\n','','cipher.py is licensed under',
    'The Creative Commons Attribution-NonCommercial 4.0 International License',
    '\n'*2,'File Name: '+__file_name__,'\n','Author: '+__author__,
    '\n','Copyright: '+__copyright__,'\n','Credits: '+__credits__,
    '\n','DCT URL: ','\n',__dct_url__,'\n','License: '+__license__,
    '\n','Release URL: ','\n',__rel_url__,'\n','Version: '+__version__,
    '\n','Maintainer: '+__maintainer__,'\n','Email: '+__email__,'\n')

SYM = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
MAX_KEY_SIZE = len(SYM)

def gMode():
    while True:
        print('\n','Type "e" to encrypt or... Type "d" to decrypt:','\n')
        mode = input().lower()
        if mode in ['e','E','d','D']:
            return mode
        else:
            print('ERROR!:','\n'+'Invalid Symbol or Outside Perameters','\n')

def gMessage():
    print('Type a message:')
    return input()

def gKey():
    key = 0
    while True:
        print('Shift Strength(1-%s)' % (MAX_KEY_SIZE))
        key = int(input())
        if (key >= 1 and key <= MAX_KEY_SIZE):
            return key

def gTranslated(mode, message, key):
    if mode[0] == 'd':
        key = -key
    translated = ''
    for symbol in message:
        symbolIndex = SYM.find(symbol)
        if symbolIndex == -1:
        # Symbol not within MAX_KEY_SIZE parameters.
            translated += symbol
        else:
        # Encryption or Decryption Magic!
            symbolIndex += key
        if symbolIndex >= len(SYM):
            symbolIndex -= len(SYM)
        elif symbolIndex < 0:
            symbolIndex += len(SYM)
        translated += SYM[symbolIndex]
    return translated

mode = gMode()
message = gMessage()
key = gKey()

print('\n','Translated:', gTranslated(mode, message, key),'\n')

#end