chrislit / abydos

    return 1 - sim_prefix(src, tar)

def sim_suffix(src, tar):

    """Return the suffix similarity of two strings.

    Suffix similarity is the ratio of the length of the shorter term that

    exactly matches the longer term to the length of the shorter term,

    beginning at the end of both terms.

    :param str src, tar: two strings to be compared

    :returns: suffix similarity

    :rtype: float

    >>> sim_suffix('cat', 'hat')

    0.6666666666666666

    >>> sim_suffix('Niall', 'Neil')

    0.25

    >>> sim_suffix('aluminum', 'Catalan')

    0.0

    >>> sim_suffix('ATCG', 'TAGC')

    0.0

    """

    if src == tar:

        return 1.0

    if not src or not tar:

        return 0.0

    min_word, max_word = (src, tar) if len(src) < len(tar) else (tar, src)

    min_len = len(min_word)

    for i in range(min_len, 0, -1):

        if min_word[-i:] == max_word[-i:]:

            return i/min_len

    return 0.0

def dist_suffix(src, tar):

    """Return the suffix distance between two strings.

    return 1 - sim_length(src, tar)

def sim_prefix(src, tar):

    """Return the prefix similarty of two strings.

    Prefix similarity is the ratio of the length of the shorter term that

    exactly matches the longer term to the length of the shorter term,

    beginning at the start of both terms.

    :param str src, tar: two strings to be compared

    :returns: prefix similarity

    :rtype: float

    >>> sim_prefix('cat', 'hat')

    0.0

    >>> sim_prefix('Niall', 'Neil')

    0.25

    >>> sim_prefix('aluminum', 'Catalan')

    0.0

    >>> sim_prefix('ATCG', 'TAGC')

    0.0

    """

    if src == tar:

        return 1.0

    if not src or not tar:

        return 0.0

    min_word, max_word = (src, tar) if len(src) < len(tar) else (tar, src)

    min_len = len(min_word)

    for i in range(min_len, 0, -1):

        if min_word[:i] == max_word[:i]:

            return i/min_len

    return 0.0

def dist_prefix(src, tar):

    """Return the prefix distance between two strings.