Hamming distance between two binary strings not working

Implement it:

def hamming2(s1, s2):
    """Calculate the Hamming distance between two bit strings"""
    assert len(s1) == len(s2)
    return sum(c1 != c2 for c1, c2 in zip(s1, s2))

And test it:

assert hamming2("1010", "1111") == 2
assert hamming2("1111", "0000") == 4
assert hamming2("1111", "1111") == 0

If we are to stick with the original algorithm, we need to convert the strings to integers to be able to use the bitwise operators.

def hamming2(x_str, y_str):
    """Calculate the Hamming distance between two bit strings"""
    assert len(x_str) == len(y_str)
    x, y = int(x_str, 2), int(y_str, 2)  # '2' specifies we are reading a binary number
    count, z = 0, x ^ y
    while z:
        count += 1
        z &= z - 1  # magic!
    return count

Then we can call it as follows:

print(hamming2('100010', '101000'))

While this algorithm is cool as a novelty, having to convert to a string likely negates any speed advantage it might have. The answer @dlask posted is much more succinct.

This is what I use to calculate the Hamming distance.
It counts the # of differences between equal length strings.

def hamdist(str1, str2):
    diffs = 0
    for ch1, ch2 in zip(str1, str2):
        if ch1 != ch2:
            diffs += 1
    return diffs