If (assuming this is correct, you can do more tests) the given strings are many and/or long, this can be a fast version. With Psyco this same version can become quite faster. Bye, bearophile
from array import array class ToBinary(object): """ToBinary: class to convert a given string to a binary string.""" def __init__(self): _nibbles = {"0":"0000", "1":"0001", "2":"0010", "3":"0011", "4":"0100", "5":"0101", "6":"0110", "7":"0111", "8":"1000", "9":"1001", "A":"1010", "B":"1011", "C":"1100", "D":"1101", "E":"1110", "F":"1111"} self._bytes = ["".join(_nibbles[h] for h in "%X"%i).zfill(8) for i in xrange(256)] def conv(self, s): if s: result = [self._bytes[el] for el in array("B", s)] result[0] = result[0].lstrip("0") return "".join(result) else: return "0" # Tests Conv2 = ToBinary() data = ["", "a", "b", "ab", "hello", "123456789"] for s in data: print s, Conv2.conv(s) -- http://mail.python.org/mailman/listinfo/python-list