networkx.algorithms.shortest_paths.weighted.multi_source_dijkstra_path_length

multi_source_dijkstra_path_length(G, sources, cutoff=None, weight='weight')[source]

Find shortest weighted path lengths in G from a given set of source nodes.

Compute the shortest path length between any of the source nodes and all other reachable nodes for a weighted graph.

Parameters
  • G (NetworkX graph)

  • sources (non-empty set of nodes) – Starting nodes for paths. If this is just a set containing a single node, then all paths computed by this function will start from that node. If there are two or more nodes in the set, the computed paths may begin from any one of the start nodes.

  • cutoff (integer or float, optional) – Depth to stop the search. Only return paths with length <= cutoff.

  • weight (string or function) – If this is a string, then edge weights will be accessed via the edge attribute with this key (that is, the weight of the edge joining u to v will be G.edges[u, v][weight]). If no such edge attribute exists, the weight of the edge is assumed to be one.

    If this is a function, the weight of an edge is the value returned by the function. The function must accept exactly three positional arguments: the two endpoints of an edge and the dictionary of edge attributes for that edge. The function must return a number.

Returns

length – Dict keyed by node to shortest path length to nearest source.

Return type

dict

Examples

>>> G = nx.path_graph(5)
>>> length = nx.multi_source_dijkstra_path_length(G, {0, 4})
>>> for node in [0, 1, 2, 3, 4]:
...     print('{}: {}'.format(node, length[node]))
0: 0
1: 1
2: 2
3: 1
4: 0

Notes

Edge weight attributes must be numerical. Distances are calculated as sums of weighted edges traversed.

The weight function can be used to hide edges by returning None. So weight = lambda u, v, d: 1 if d['color']=="red" else None will find the shortest red path.

Raises
  • ValueError – If sources is empty.

  • NodeNotFound – If any of sources is not in G.