When you are adding a new property to a graph-tool graph (https://graph-tool.skewed.de/) is_node_customer = network.new_vertex_property("bool") weight = network.new_edge_property("float") you should never forget to add this network.vertex_properties["is_node_customer"] = is_node_customer network.edge_properties["weight"] = weight Otherwise the properties will not saved or stored together with the graph and you will lose a lot of time
The technical blog of Francesco De Collibus.