Check has edge for undirected graph

Question

I need to check if there is an edge between vertices in a undirected graph.

I tried this:

from igraph import *
g = Nexus.get("karate")
print "is directed: ", g.is_directed()
print "0,1: ", g.es.select(_from=0, _target=1)['weight']
print "1,0: ", g.es.select(_from=1, _target=0)['weight']

# Output
is directed: False
0,1:  [4.0]
1,0:  []

But, I want this result:

# Output
is directed: False
0,1:  [4.0]
1,0:  [4.0]

Answer 1

This is probably a bug in g.es.select. Why not use g.es[g.get_eid(0, 1)]['weight'] instead? g.es.select is slow anyway if you only need a single edge.