cipher.py

   1 import string
   2 import collections
   3
   4 english_counts = collections.defaultdict(int)
   5 with open('count_1l.txt', 'r') as f:
   6     for line in f:
   7         (letter, count) = line.split("\t")
   8         english_counts[letter] = int(count)
   9
  10 def sanitise(text):
  11     sanitised = [c.lower() for c in text if c in string.ascii_letters]
  12     return ''.join(sanitised)
  13
  14 def letter_frequencies(message):
  15     frequencies = collections.defaultdict(int)
  16     for letter in sanitise(message):
  17         frequencies[letter]+=1
  18     return frequencies
  19
  20 def caesar_cipher_letter(letter, shift):
  21     if letter in string.ascii_letters:
  22         if letter in string.ascii_lowercase:
  23             return chr((ord(letter) - ord('a') + shift) % 26 + ord('a'))
  24         else:
  25             new_letter = letter.lower()
  26             yolo = chr((ord(new_letter) - ord('a') + shift) % 26 + ord('a'))
  27             return yolo.upper()
  28     else:
  29         return letter
  30
  31 def caesar_decipher_letter(letter, shift):
  32     return caesar_cipher_letter(letter, -shift)
  33
  34 def caesar_cipher_message(message, shift):
  35     big_cipher = [caesar_cipher_letter(l, shift) for l in message]
  36     return ''.join(big_cipher)
  37
  38 def caesar_decipher_message(message, shift):
  39     return caesar_cipher_message(message, -shift)