Adjacency matrix in Python

Question

I cannot find any clear explanation as to how to create an adjacency matrix in Python, with weights taken into consideration. I assume it should be relatively simple to create.<

Answer 1

As mentioned previously, the standard way to deal with matrices in Python is to use NumPy. Here's a function that simply reads the adjacency matrix off of the adjacency list. (The implicit ordering of the nodes is made explicit by the parameter nodes.)

import numpy

def weighted_adjmatrix(adjlist, nodes):
    '''Returns a (weighted) adjacency matrix as a NumPy array.'''
    matrix = []
    for node in nodes:
        weights = {endnode:int(weight)
                   for w in adjlist.get(node, {})
                   for endnode, weight in w.items()}
        matrix.append([weights.get(endnode, 0) for endnode in nodes])
    matrix = numpy.array(matrix)
    return matrix + matrix.transpose()

In this case, weighted_adjmatrix(graph, nodes=list('123456')) gives the NumPy array

array([[ 0, 15,  0,  7, 10,  0],
       [15,  0,  9, 11,  0,  9],
       [ 0,  9,  0,  0, 12,  7],
       [ 7, 11,  0,  0,  8, 14],
       [10,  0, 12,  8,  0,  8],
       [ 0,  9,  7, 14,  8,  0]])

If a regular list is desired, the method tolist() can be called.