embed hidden messages into standard text/string using zero width characters

stringenc.py

ZERO_WIDTH_JOINER = '\u200d'
ZERO_WIDTH_SPACE = '\u200b'
ZERO_WIDTH_NON_JOINER = '\u200c'
ZERO_WIDTH_NO_BREAK_SPACE = '\ufeff'

def zeropad(num, padding=8):
    return str(num).zfill(padding)

def num_to_binary(num):
    return bin(num)[2:]

def text_to_binary(username):
    res = []
    for c in username:
        binary = num_to_binary(ord(c[0]))
        res.append(zeropad(binary))
    return ' '.join(res)

def binary_to_text(string):
    bins = string.split(' ')
    res = []
    for b in bins:
        res.append(chr(int(b, 2)))
    return ''.join(res)

def binary_to_zerowidth(binary):
    res = []
    for b in binary:
        if b == ' ':
            res.append(ZERO_WIDTH_JOINER)
        elif int(b) == 1:
            res.append(ZERO_WIDTH_SPACE)
        elif int(b) == 0:
            res.append(ZERO_WIDTH_NON_JOINER)
    return ZERO_WIDTH_NO_BREAK_SPACE.join(res)

def zerowidth_to_binary(string):
    chars = string.split(ZERO_WIDTH_NO_BREAK_SPACE)
    res = []
    for c in chars:
        if c == ZERO_WIDTH_SPACE:
            res.append('1')
        elif c == ZERO_WIDTH_NON_JOINER:
            res.append('0')
        elif c == ZERO_WIDTH_JOINER:
            res.append(' ')
    return ''.join(res)


def main():
    hidden_string = "fuck you"
    string = "i am paradox"
    print("Before encoding, Original Message:\n{}".format(string))

    string_binary = text_to_binary(hidden_string)
    string_zeropad = binary_to_zerowidth(string_binary)

    string_enc = string + string_zeropad
    print("After encoding with hidden message '{}' : \n{}".format(hidden_string, string_enc))

    zb = zerowidth_to_binary(string_zeropad)
    hidden = binary_to_text(zb)

if __name__ == "__main__":
    main()