Hi tiago, I was thinking if there is an efficient way to assing values to a vector property map. The only working method that I can use is the following: vprop = g.new_vertex_property("vector<double>") for i in range(G.num_vertices()): vprop[G.vertex(i)] = [1,2,3] When I try to use something like this: index = np.where(some condition on vertex properties)[0] vprop.a[index] = [1,2,3] It gives me the error: "TypeError: 'NoneType' object does not support item assignment". The error comes only with vector< > type properties. I am using this to assing colours to some vertices if a given condition is satified. I hope that you can help, because the first method is really slow on graphs with hundred of thousands vertices. -- Sent from: http://main-discussion-list-for-the-graph-tool-project.982480.n3.nabble.com/