# Download the following two text files (famous English books): 
#
#    http://www.samyzaf.com/braude/PYTHON/projects/jude.txt 
#    http://www.samyzaf.com/braude/PYTHON/projects/oliver_twist.txt 
#
# Write a Python function letter_frequency(file) for counting English 
# letters frequency in a text file.
# Your program output should look like: 
#       a 0.07660
#       b 0.01401
#       c 0.02301
#       d 0.04541
#       e 0.12475
#       f 0.01936
#       g 0.02069
#       h 0.06534
#       i 0.06234
#       ...
#       A 0.00222
#       B 0.00108
#       C 0.00075
#       D 0.00050
#       E 0.00058
#       F 0.00045
#       G 0.00049
#       ...
# - The frequency of a letter is defined as the ratio between the number
#   of its occurrences and the total number of letters in the text
#   (make sure to ignore characters that are not English letters!). 
# - Print the frequency tables for the two books. 
# - Do you notice any similarities between the two tables? 
# - Hints: Import the string module and look at string.letters data member
#   Use a dictionary to hold a mapping between a letter and its number of occurrences. 

import string, random

def letter_frequency(textfile):
    f = file(textfile, 'r')
    d = dict()
    for letter in string.letters:
        d[letter] = 0
    total_letters = 0
    for line in f:
        for letter in line:
            if letter in d:
                total_letters += 1
                d[letter] += 1
    f.close()
    for letter in d:
        d[letter] = d[letter] / float(total_letters)
    for letter in string.letters:
        print letter, d[letter]
    return d

def random_cipher():
    Letters = list(string.letters)
    random.shuffle(Letters)
    cipher = dict()
    for letter in string.letters:
       cipher[letter] = Letters.pop()
    return cipher

def file_encrypt(filename, outfile, cipher):
    f1 = file(filename, 'r')
    f2 = file(outfile, 'w')
    for line in f1:
        for char in line:
            if char in cipher:
                char = cipher[char]
            f2.write(char)
    f2.close()
    f1.close()

if __name__ == '__main__':
    letter_frequency("D:/workspace/jude.txt")
    cipher = random_cipher()
    file_encrypt("d:/workspace/jude.txt", "d:/workspace/jude_encripted.txt", cipher)