import string
+import collections
+english_counts = collections.defaultdict(int)
+with open('count_1l.txt', 'r') as f:
+ for line in f:
+ (letter, count) = line.split("\t")
+ english_counts[letter] = int(count)
+
+def sanitise(text):
+ sanitised = [c.lower() for c in text if c in string.ascii_letters]
+ return ''.join(sanitised)
+
+def letter_frequencies(message):
+ frequencies = collections.defaultdict(int)
+ for letter in sanitise(message):
+ frequencies[letter]+=1
+ return frequencies
def caesar_cipher_letter(letter, shift):
if letter in string.ascii_letters: