def binaryStringDigitDiff(binstr1, binstr2):
    """
    Count the number of digits that differ between two
    same-length binary strings

    Parameters
    ----------
    binstr1 : string
        A binary (base-2) numeric string.
    binstr2 : string
        A binary (base-2) numeric string.

    Returns
    -------
    An integer, the number of digits that differ between
    the two strings.

    """
    digitDiff = 0
    if not len(binstr1) == len(binstr2):
        raise Exception("binaryStringDigitDiff requires arguments to have same length")
    for n in range(0, len(binstr1)):
        if binstr1[n] != binstr2[n]:
            digitDiff += 1
    return digitDiff