在python中将有向图转换为无向图（列表数组）的快速方法？

Question

I'm trying to convert a set of arcs to a set of edges for some simple visualization work.

my arc data currently looks like:

(
  ['A','B',2],
  ['B','A',3],
  ['A','C',4],
  ['B','C',2],
)

I need to convert it to edges, so the directions are combined, looking like this:

(
  ['A','B',5],
  ['A','C',4],
  ['B','C',2],
)

I'm thinking there should be a very pythonic way to do this, but not sure what the most elegant way is.

Answer 1

Here's an approach using a dictionary where the keys are the ends of the arc in sorted order:

import collections
d = collections.defaultdict(int)
for n1, n2, v in arcdata:
    d[min(n1, n2), max(n1, n2)] += v
result = [[k[0], k[1], v] for k, v in d.iteritems()]