Perhaps this is what you're looking for:
def XorBlock(block1, block2):
l = len(block1)
if l != len(block2):
raise ValueError
# |-> Converting into int
return [(int(block1[j])+int(block2[j])) % 2 for j in xrange(l)]
# |-> Converting into int
if __name__ == '__main__':
print XorBlock("12345", "23456")
>>> XorBlock("010101", "108734")
[1, 1, 0, 0, 1, 1]
I decided that keeping both arguments as strings would be best, as in binary, you may have to have some 0
s before any digits of value.