hideMessage_textstego1.py

import sys
import os

def to_binary_string(s):
    binary_s = ''
    for c in s:
        binary_s += '{:08b}'.format(ord(c))
    return binary_s

def main():
    if len(sys.argv) != 4:
        print 'Usage: python %s <input-file> <message> <output-file>' % sys.argv[0]
        exit(1)

    input_file   = sys.argv[1]
    message      = sys.argv[2]
    output_file  = sys.argv[3]

    if not os.path.exists(input_file):
        print 'File "%s" does not exist' % input_file
        exit(1)


    message_binary = to_binary_string(message)

    with open(input_file) as f:
        container = f.read()

    words = container.split(' ')

    message_binary += '0' * (len(words) - len(message_binary))
    for i in range(len(message_binary)):
        if message_binary[i] == '0':
            words[i] += ' ' # 1 space
        else:
            words[i] += '  ' # 2 spaces

    with open(output_file, 'w') as f:
        f.write(''.join(words))

if __name__ == '__main__':
    main()