Re: [igraph] how to select eid on the basis of an edge attribute

[Tamas Nepusz]

> I guess this can work:
Yup, this can work, but this one might be faster:

nei_edges = g.adjacent(v1, type="in")
friends = [edge.tuple[0] for edge in g.es.select(nei_edges,  
color="blue")]

(note that in a directed graph, this applies only to incoming edges.  
In an undirected graph, type="..." is ignored and you get all the  
adjacent edges).

The reason why it is faster is that Python handles list comprehensions  
(expressions like [foo for foo in bar]) faster than "real" for loops.  
(Also, g.es.select(nei_edges, color="blue") selects all the blue edges  
among nei_edges in the C layer at once).

--
T.

> friend=[]
> nei_edges = g.adjacent(v1, type="in")
> for nei_edge in nei_edges:
>   if g.es[nei_edge]["color"] == "blue":
>         friend.append(g.es[nei_edge].tuple[0])
>
> cheers,
> Simone
>
> 2009/1/22 Tamas Nepusz <address@hidden>:
> > Hi Simone,
> >
> > > Could this be the a good strategy?
> > >
> > > 1) find all the neighbors of v1:
> > >
> > > 2) for each neighbor in the list:
> > >
> > > 3) check if they are blue-linked with v1 (using get_eids()):
> >
> > Yup, but since you will be checking the _edges_ adjacent to v1, you  
> > should
> > find the adjacent edges in step 1 instead of the neighbours. So:
> >
> > nei_edges = g.adjacent(v1)
> > for nei_edge in nei_edges:
> > if g.es[nei_edge]["color"] == "blue":
> >   # do this
> > else:
> >   # do that
> >
> > --
> > T.
> >
> >
> > _______________________________________________
> > igraph-help mailing list
> > address@hidden
> > http://lists.nongnu.org/mailman/listinfo/igraph-help
>
>
> _______________________________________________
> igraph-help mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/igraph-help