在igraph-python中按照指示处理的无向图

Question

I have a graph that I create by reading in a GML file. I'm trying to find all of the edges that touch a node N. My code is as follows:

self.simGraph = Graph.Read_GML(file_name)
node = self.simGraph.vs.find(title=title)
edge_set = self.simGraph.es.select(_source=node.index)

I noticed, when debugging, that edge_set would often contain only one edge, but when I changed _source to _target , I would get a different set of edges. I tried adding

self.simGraph = self.simGraph.as_undirected() 

but got the same results.

Am I missing something?

Answer 1

You might be getting different sets of edges when you use the current vertex as 'source' or 'target'. It seems like igraph is randomly assigning 'source' and 'target' roles to vertices for undirected networks but it knows that the network is undirected. Even if you generate an undirected network from scratch, the set of edges connected to a vertex will be different when you set that vertex as a source or a target. If you want to get a list of edges (id's) incident on ao vertex i, use the following

g.incident(i)