def nearest(a: list, b: list) -> list:
    """
    For each item in list a, find the nearest value in list b, and return a
    list of tuples with these associations.
    """
    ret = list()

    for item in a:
        candidates = sorted([(v, abs(item-v)) for v in b], key=lambda t: t[1])
        ret.append((item, candidates[0][0]))

    return ret