dijkstra_for_adjacency_matrix.py

import heapq
def dijkstra(cost_matrix, destination_node):
    open_list = []
    closed_list = set()
    number_of_nodes = len(cost_matrix)
    # (cum_cost, (previous_node, current_node))
    heapq.heappush(open_list, (0, (0, 0)))
    while open_list:
        current_node = heapq.heappop(open_list)
        # if the current node not already expanded
        if current_node[1][1] not in closed_list:
            closed_list.add(current_node[1][1])
            if destination_node == current_node[1][1]:
                return current_node
            # expand
            for next_node in range(number_of_nodes):
                cost = cost_matrix[current_node[1][1]][next_node]
                heapq.heappush(open_list, (cost+current_node[0], (current_node[1][1] ,next_node))) if next_node not in closed_list else None
    return None 

cost_matrix = [[ 0    ,20,  30,  100 ],
[ 20   ,0   ,15  ,75  ],
[ 30   ,15  ,0   ,50  ],
[ 100  ,75  ,50  ,0   ]]

dijkstra(cost_matrix, destination_node=3)