Some easy-to-use best matches seeker using linear search (possible improvements on the sorting loop

match.py

def matches(target: str, data: str, cutoff: float):
    if len(target) == 0:
        raise ZeroDivisionError("Data must be at leat one character long")
    score = 0.0
    for target_letter_index in range(len(target)):
        if target[target_letter_index] in data:
            score += .5
            if target_letter_index < len(data) and data[target_letter_index] == target[target_letter_index]:
                score += .5
    score /= len(target)
    return score >= cutoff, score


def close_matches(target: str, data: list, cutoff: float = 0.5, amount: int = 5, function=lambda x: x):
    found = []
    for reading in data:
        reading_passes, reading_affinity = matches(target.lower(),
                                                   function(reading).lower(), cutoff=cutoff)
        if reading_passes:
            insert_index = len(found)
            finished = False
            i = 0
            while i < len(found) and not finished:
                if found[i][1] < reading_affinity:
                    insert_index = i
                    finished = True
                else:
                    i += 1
            found.insert(insert_index, (reading, reading_affinity))
    return found[:amount]