2.8. Multigraphs¶

NetworkX provides classes for graphs which allow multiple edges between any pair of nodes. The MultiGraph and MultiDiGraph classes allow you to add the same edge twice, possibly with different edge data. This can be powerful for some applications, but many algorithms are not well defined on such graphs. Shortest path is one example. Where results are well defined, e.g. MultiGraph.degree() we provide the function. Otherwise you should convert to a standard graph in a way that makes the measurement well defined.

>>> MG=nx.MultiGraph()
>>> MG.add_weighted_edges_from([(1,2,.5), (1,2,.75), (2,3,.5)])
>>> MG.degree(weight='weight')
{1: 1.25, 2: 1.75, 3: 0.5}
>>> GG=nx.Graph()
>>> for n,nbrs in MG.adjacency_iter():
...    for nbr,edict in nbrs.items():
...        minvalue=min([d['weight'] for d in edict.values()])
...        GG.add_edge(n,nbr, weight = minvalue)
...
>>> nx.shortest_path(GG,1,3)
[1, 2, 3]