form edge between nodes by attribute look up in igraph in python

Question

I have a graph g and it has a 'name' attribute associated with each node. I would like to call two nodes by their name attributes and create an edge between them.

from igraph import *
g = Graph(4)

print g
IGRAPH UN-- 4 0 --
+ attr: name (v)

g.vs["name"]
[10, 39, 76, 6]

However, when I try something like

g.add_edge(g.vs[76], g.vs[39]) 

I get a vertex index out of range. I would be happy with a solution that calls a node by it's index if I could match name to index position as long as it's fast, because my graph can get quite large and I do not know how slow that will become.

Ideally, I would just look up nodes by their 'name' attributes and form an edge between them.

Answer 1

You are indexing the names based on their position in the name vector, as you probably guessed. You can match the name to its position in the name vector:

v1_position = g.vs['name'].index(76)
v2_position = g.vs['name'].index(39)

g.add_edge(v1_position, v2_position)