Hi Jean-Patrick, I think a faster way could be using the degree_property_map associated to the graph: kp = T.degree_property_map('out') and filter it using your favorite function (the first that comes to my mind is. np.equal(kp.a, np.ones(T.num_vertices(),dtype=np.int)) ). You can then use the resulting array to select the vertices to inspect. I expect an equality between N integers to be faster than N append. Best, Giuseppe Il giorno mer 7 ott 2015 alle ore 00:04 jean-patrick < jeanpatrick.pommier@gmail.com> ha scritto:

Hello,

Is there an obvious way to collect vertices of degree 1 for reading the property of their edge?

The following code succeed in doing the job on a tiny scale, but I am sure this not the way to do:

/import graph_tool.all as gt #from graph_tool import topology

## Make a graph

T = gt.Graph(directed = False) edge_weights = T.new_edge_property('double') T.properties[("e","weight")] = edge_weights

T.add_vertex(n=5)

e_1 = T.add_edge(0,1) e_2 = T.add_edge(1,2) e_3 = T.add_edge(0,0) e_4 = T.add_edge(1,3)

edge_weights[e_1]= 2 edge_weights[e_2]= 6 edge_weights[e_3]= 1 edge_weights[e_4]= 3

## Get the vertices of degree 1 in a dictionary (keys= vertices degree, values=vertices)

from collections import defaultdict deg_dic = defaultdict(list)

for v in T.vertices(): degree = v.out_degree() deg_dic[degree].append(v)

## Read the weight of the bounded edge

print 'vertices of degree 1:' for d1 in deg_dic[1]: weight_of_bound_edge = [edge_weights[e] for e in d1.out_edges()] print 'vertex',d1,' weight of out edge:', weight_of_bound_edge/

By the way, the objective is to count the vertices of degree 1 as a function of the pruning steps. Is there sucha a function in graph-tool?

Best regards

Jean-Patrick

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