convert a long string in binary

[bearophileHUGS at lycos.com]

bussiere maillist:
> i've got a very long string
> and i wanted to convert it in binary

Not much tested:

_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"}

def toBase2(number):
    if number < 16:
        return "0000" + _nibbles["%X" % number]
    else:
        d1, d2 = "%X" % number
        return _nibbles[d1] + _nibbles[d2]

convbin = dict((chr(i), toBase2(i)) for i in xrange(256))

def binary(s):
    return "".join(convbin[c] for c in s)

print binary("testing string")

Surely there are ways to make it shorter (But it's fast enough).

Bye,
bearophile