shortest_path_length

shortest_path_length(G, source=None, target=None, weight=None)

Compute shortest path lengths in the graph.

This function can compute the single source shortest path lengths by specifying only the source or all pairs shortest path lengths by specifying neither the source or target.

Parameters :

G : NetworkX graph

source : node, optional

Starting node for path. If not specified compute shortest path lengths for all connected node pairs.

target : node, optional

Ending node for path. If not specified compute shortest path lengths for every node reachable from the source.

weight : None or string, optional (default = None)

If None, every edge has weight/distance/cost 1. If a string, use this edge attribute as the edge weight. Any edge attribute not present defaults to 1.

Returns :

length : number, or container of numbers

If the source and target are both specified return a single number for the shortest path. If only the source is specified return a dictionary keyed by targets with a the shortest path as keys. If neither the source or target is specified return a dictionary of dictionaries with length[source][target]=value.

Raises :

NetworkXNoPath :

If no path exists between source and target.

See also

all_pairs_shortest_path_length, all_pairs_dijkstra_path_length, single_source_shortest_path_length, single_source_dijkstra_path_length

Notes

For digraphs this returns the shortest directed path. To find path lengths in the reverse direction use G.reverse(copy=False) first to flip the edge orientation.

Examples

>>> G=nx.path_graph(5)
>>> print(nx.shortest_path_length(G,source=0,target=4))
4
>>> p=nx.shortest_path_length(G,source=0) # target not specified
>>> p[4]
4
>>> p=nx.shortest_path_length(G) # source,target not specified
>>> p[0][4]
4