pythonnetworkxdgl

How to get node weights from networkx to dgl


Consider the following toy networkx graph:

import networkx as nx
G = nx.DiGraph()
G.add_edges_from([(0, 1), (1, 2), (2, 3)])
G.nodes[0]["weight"] = 0
G.nodes[1]["weight"] = 10
G.nodes[2]["weight"] = 20
G.nodes[3]["weight"] = 30

I would like to use that in dgl but I am not sure how to read in the node weights. I attempted:

import dgl
dgl.from_networkx(G, node_attrs="weight")

but that gives:

File ~/venv/lib/python3.8/site-packages/dgl/convert.py:1279, in from_networkx(nx_graph, node_attrs, edge_attrs, edge_id_attr_name, idtype, device)
   1277 for nid in range(g.number_of_nodes()):
   1278     for attr in node_attrs:
-> 1279         attr_dict[attr].append(nx_graph.nodes[nid][attr])
   1280 for attr in node_attrs:
   1281     g.ndata[attr] = F.copy_to(_batcher(attr_dict[attr]), g.device)

KeyError: 'w'

What is the right way to do this?


Solution

  • From the dgl doc here, it looks like node_attrs should be a list of attribute names. So if you change dgl.from_networkx(G, node_attrs="weight") to dgl.from_networkx(G, node_attrs=["weight"]), you will get the result you want.

    See code below:

    import networkx as nx
    import dgl
    
    G = nx.DiGraph()
    G.add_edges_from([(0, 1), (1, 2), (2, 3)])
    G.nodes[0]["weight"] = 0
    G.nodes[1]["weight"] = 10
    G.nodes[2]["weight"] = 20
    G.nodes[3]["weight"] = 30
    
    dgl.from_networkx(G, node_attrs=["weight"])
    

    And output:

    Graph(num_nodes=4, num_edges=3,
          ndata_schemes={'weight': Scheme(shape=(), dtype=torch.int64)}
          edata_schemes={})