fileencrypt.py

from simplecrypt import encrypt, decrypt
from os.path import exists
from os import unlink

PASSWORD = "secret"
FILENAME = "encrypted.txt"


def main():
    # read or create the file
    if exists(FILENAME):
        print("reading...")
        data = read_encrypted(PASSWORD, FILENAME)
        print("read %s from %s" % (data, FILENAME))
        n_bottles = int(data.split(" ")[0]) - 1
    else:
        n_bottles = 10
    # write the file
    if n_bottles > 0:
        data = "%d green bottles" % n_bottles
        print("writing...")
        write_encrypted(PASSWORD, FILENAME, data)
        print("wrote %s to %s" % (data, FILENAME))
    else:
        unlink(FILENAME)
        print("deleted %s" % FILENAME)


def read_encrypted(password, filename, string=True):
    with open(filename, 'rb') as input_file:
        ciphertext = input_file.read()
        plaintext = decrypt(password, ciphertext)
        if string:
            return plaintext.decode('utf8')
        else:
            return plaintext


def write_encrypted(password, filename, plaintext):
    with open(filename, 'wb') as output:
        ciphertext = encrypt(password, plaintext)
        output.write(ciphertext)

if __name__ == '__main__':
    main()