Find all permutations of a list of integers that add up to another integer

permutations_of_sum.py

def find_two_tuple_permutations(n, k):
	n = set(n)
	valid_pairs = []
	for i in n:
	    delta = k - i
	    if delta in n:
	        valid_pairs.append((i, delta))
	return valid_pairs


def find_three_tuple_permutations(n, k):
    n = set(n)
    valid_triplets = []
    for i in n:
        delta = k - i
        valid_pairs = find_two_tuple_permutations(n, delta)
        for pair in valid_pairs:
            valid_triplets.extend([i, valid_pairs[0], valid_pairs[1]])
    return valid_triplets

n = [2, 4, 1, -56, 7]
k = 7

find_three_tuple_permutations(n, k)