fs-decrypt.py

#!/usr/bin/env python


import string

new_alphabet = string.lowercase
top_right_alphabet = new_alphabet.replace('q', '')

new_alphabet = top_right_alphabet

keyword_one = 'exampl'
keyword_two = 'keyword'
encrypted_text = 'FYGMKYHOBXMFKKKIMD'

for char in keyword_one:
    top_right_alphabet = top_right_alphabet.replace(char, '')
top_right = keyword_one + top_right_alphabet


bottom_left_alphabet = new_alphabet
for char in keyword_two:
    bottom_left_alphabet = bottom_left_alphabet.replace(char, '')
bottom_left = keyword_two + bottom_left_alphabet.replace('q', '')

n = 5

bottom_left = [bottom_left[i:i+n] for i in range(0, len(bottom_left), 5)]
top_right = [top_right[i:i+n] for i in range(0, len(top_right), 5)]
new_alphabet_rows = [new_alphabet[i:i+n] for i in range(0, len(new_alphabet), 5)]

print 'top_right:'
p = 0
for each in top_right:
    print '\t%s\t%s' % (new_alphabet_rows[p], each)
    p += 1

print 'bottom_left:'
q = 0
for each in bottom_left:
    print '\t%s\t%s' % (each, new_alphabet_rows[q])
    q += 1


original_message = str()

k = 0
while k < len(encrypted_text):
    one = encrypted_text[k]
    two = encrypted_text[k + 1]

    one_pos = ''.join(top_right).find((one).lower())
    two_pos = ''.join(bottom_left).find((two).lower())

    one_col = one_pos % 5
    if one_col == 0 or one_col == 5:
        one_row = one_pos / 5
    else:
        one_row = (one_pos / 5)

    two_col = two_pos % 5
    if two_col == 0 or two_col == 5:
        two_row = two_pos / 5
    else:
        two_row = (two_pos / 5)


    first_out_char = new_alphabet_rows[one_row][two_col]
    second_out_char = new_alphabet_rows[two_row][one_col]

    original_message += first_out_char + second_out_char
    k += 2

print (original_message).upper()