程序帮我加上输出每次选择的最短边的初始节点和终止节点，注意是每次选择的最短边，

好的，根据您的要求，我已经修改了代码，现在输出每次选择的最短边的初始节点和终止节点。请查看以下代码：

from collections import defaultdict
import heapq

def dijkstra(edges, start_node, end_node):
    graph = defaultdict(list)
    # 构建图
    for edge in edges:
        source, dest, weight = edge
        graph[source].append((weight, source, dest))
    # 初始化距离
    distances = {node: float('inf') for node in graph}
    distances[start_node] = 0
    # 初始化堆
    heap = [(0, start_node, [])]
    # Dijkstra算法
    while heap:
        (cost, current_node, path) = heapq.heappop(heap)
        if current_node == end_node:
            return (cost, path)
        if distances[current_node] < cost:
            continue
        for edge in graph[current_node]:
            weight, source, dest = edge
            new_cost = cost + weight
            new_path = path + [(source, dest)]
            if distances[dest] > new_cost:
                distances[dest] = new_cost
                heapq.heappush(heap, (new_cost, dest, new_path))
        # 输出每次选择的最短边的初始节点和终止节点
        if path:
            print("Selected edge: ", path[-1][0], "->", path[-1][1])
    return float('inf')

现在在每次选择最短边时，会输出该边的初始节点和终止节点。