gistfile1.py

face_list = set()
edge_list = set()
connections = defaultdict(set)
for a, b in edges:
	connections[a] |= {b}
	connections[b] |= {a}
	common = connections[a] & connections[b]
	for x in common:
		forward_order = {(x, a),(a, b),(b, x)}
		reverse_order = {(a, x),(x, b),(b, a)}
		if not forward_order & edge_list:
			face_list.add((x, a, b))
			edge_list |= forward_order

		elif not reverse_order & edge_list:
			face_list.add((a, x, b))
			edge_list |= reverse_order
		else:
			print "hmm"
			face_list.add((b, x, a))
			edge_list.update([(b, x),(x, a),(a, b)])