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

Find shortest weighted path lengths in G from a source node.

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

  • G (NetworkX graph)

  • source (node label) – Starting node for path

  • 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.


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

Return type:



NodeNotFound – If source is not in G.


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


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.