Python: XOR hex strings

Possible Duplicate:
bitwise XOR of hex numbers in python

I am trying to XOR two hex strings in Python and did not really know where to start from.

I have two hex strings:

a = "32510ba9a7b2bba9b8005d43a304b5714cc0bb0c8a34884dd91304b8ad40b62b07df44ba6e9d8a2368e51d04e0e7b207b70b9b8261112bacb6c866a232dfe257527dc29398f5f3251a0d47e503c66e935de81230b59b7afb5f41afa8d661cb"
b = "32510ba9babebbbefd001547a810e67149caee11d945cd7fc81a05e9f85aac650e9052ba6a8cd8257bf14d13e6f0a803b54fde9e77472dbff89d71b57bddef121336cb85ccb8f3315f4b52e301d16e9f52f90"

Should I be using this ?

1. return "".join([chr((x) ^ (y)) for (x,y) in zip(a[:len(b)], b)])
2. return "".join([chr(ord(x) ^ ord(y)) for (x, y) in zip(a[:len(b)], b)])

I don't understand the difference with the two codes above. Why chr and ord? I have also seen people using int(hex,16).