find all pairs in a list that add to a target number

sum2target.py

def sum2target(l, t):
    """
    :param l: list of positive itegers
    :param t: a target number
    :return: set of pairs of numbers in l that sum to t
    """
    d = {t-x: x for x in l}
    return {frozenset((x, d[x])) for x in l if x in d.keys()}


if __name__ == '__main__':
    print(sum2target((3, 4, 10, 1, 6), 7))