Using dijkstra_path function in networkx library

Question

I'm using networkx library to find shortest path between two nodes using dijkstra algo as follows

import networkx as nx

A = [[0, 100, 0, 0 , 40, 0],
     [100, 0, 20, 0, 0, 70],
     [0, 20, 0, 80, 50, 0],
     [0, 0, 80, 0, 0, 30],
     [40, 0, 50, 0, 0, 60],
     [0, 70, 0, 30, 60, 0]];

print(nx.dijkstra_path(A, 0, 4))

In the above code I'm using matrix directly, But library requires graph to be created as follows

G = nx.Graph()
G = nx.add_node(<node>)
G.add_edge(<node 1>, <node 2>)

It is very time consuming to create matrix by using above commands. Is there any way to give input as weighted matrix to the dijkstra_path function.

Answer 1

First you need to convert your adjacency matrix to a numpy matrix with np.array. Then you can simply create your graph with from_numpy_matrix.

import networkx as nx
import numpy as np

A = [[0, 100, 0, 0 , 40, 0],
     [100, 0, 20, 0, 0, 70],
     [0, 20, 0, 80, 50, 0],
     [0, 0, 80, 0, 0, 30],
     [40, 0, 50, 0, 0, 60],
     [0, 70, 0, 30, 60, 0]]

a = np.array(A)
G = nx.from_numpy_matrix(a)

print(nx.dijkstra_path(G, 0, 4))

Output:

[0, 4]

Side note: you can check the graph edges with the following code.

for edge in G.edges(data=True):
    print(edge)

Output:

(0, 1, {'weight': 100})
(0, 4, {'weight': 40})
(1, 2, {'weight': 20})
(1, 5, {'weight': 70})
(2, 3, {'weight': 80})
(2, 4, {'weight': 50})
(3, 5, {'weight': 30})
(4, 5, {'weight': 60})