how to do bitwise exclusive or of two strings in python?

Question

I would like to perform a bitwise exclusive or of two strings in python, but xor of strings are not allowed in python. How can I do it ?

Answer 1

Based on William McBrine's answer, here is a solution for fixed-length strings which is 9% faster for my use case:

import itertools
import struct
def make_strxor(size):
    def strxor(a, b, izip=itertools.izip, pack=struct.pack, unpack=struct.unpack, fmt='%dB' % size):
        return pack(fmt, *(a ^ b for a, b in izip(unpack(fmt, a), unpack(fmt, b))))
    return strxor
strxor_3 = make_strxor(3)
print repr(strxor_3('foo', 'bar'))