Re: [igraph] Extracting sub-graph

[Tamás Nepusz]

>> Have you imported the "WEAK" constant from the igraph module before? (from 
>> igraph import WEAK)
> Nope, do I need to do that?
Yes. "WEAK" is just a constant that resolves to 1, so if you want mode=WEAK to 
work, then you need to import that.

> Another issue, I use Read_Ncol() to import a large graph.
> For vertex attributes is there a similar function useful on large
> graph?
No, there isn't.

> Currently I simply loop through a list of vertices, and add the
> attributes that way, but it's slow.
You can assign attributes to a whole set of vertices like this:

g.vs["attr"] = value_list

where value_list is a list of attribute values to be assigned to the "attr" 
attribute of all the vertices. This should be faster than doing something like:

for idx, value in enumerate(value_list):
    g.vs[idx]["attr"] = value

-- 
T.