Partition a list of sets by shared elements

[ (1,2,3), (5,2,6), (7,8,9), (6,12,13), (21,8,34), (19,20) ]

[ [ (1,2,3), (5,2,6), (6,12,13) ], [ (7,8,9), (21,8,34) ], [ (19,20) ] ]

element | set_id
----------------
1       | 1
2       | 1
3       | 1
5       | 2
2       | 2
6       | 2

nodes = [ [1,2,3], [2,4,5], [6,7,8], [10,11,12], [7,10,13], [12], [] ]
links = [ set() for x in nodes ]

#first find the links
for n in range(len(nodes)):
    for item in nodes[n]:
        for m in range(n+1, len(nodes)):
            if (item in nodes[m]):
                links[n].add(m)
                links[m].add(n)

sets = []
nodes_not_in_a_set = range(len(nodes))

while len(nodes_not_in_a_set) > 0:
    nodes_to_explore = [nodes_not_in_a_set.pop()]
    current_set = set()
    while len(nodes_to_explore) > 0:
        current_node = nodes_to_explore.pop()
        current_set.add(current_node)
        if current_node in nodes_not_in_a_set:
            nodes_not_in_a_set.remove(current_node)
        for l in links[current_node]:
            if l not in current_set and l not in nodes_to_explore:
                nodes_to_explore.append(l)
    if len(current_set) > 0:
        sets.append(current_set)

for s in sets:
    print [nodes[n] for n in s]

[[]]
[[6, 7, 8], [10, 11, 12], [7, 10, 13], [12]]
[[1, 2, 3], [2, 4, 5]]