def sum_pairs(ints, s):
    """
    Given a list of integers and a single sum value,
    return the first two values (parse from the left please)
    in order of appearance that add up to form the sum.
    sum_pairs([4, 3, 2, 3, 4], 6)
        ^-----^         4 + 2 = 6, indices: 0, 2 *
        ^-----^      3 + 3 = 6, indices: 1, 3
        ^-----^   2 + 4 = 6, indices: 2, 4
    * entire pair is earlier, and therefore is the correct answer
    == [4, 2]
    """
    cache = {}
    for i in ints:
        if s - i in cache:
            return [s - i, i]
        cache[i] = i