python实现Dijkstra算法，请为我写一下它的代码

好的，以下是Python实现Dijkstra算法的代码：

import heapq

def dijkstra(graph, start, end):
    # 初始化距离字典和前驱节点字典
    distances = {vertex: float('inf') for vertex in graph}
    distances[start] = 0
    previous_vertices = {vertex: None for vertex in graph}

    # 初始化堆和访问集合
    visited = set()
    heap = [(0, start)]

    while heap:
        # 弹出堆中距离最小的节点
        (current_distance, current_vertex) = heapq.heappop(heap)

        # 如果节点已被访问，则跳过
        if current_vertex in visited:
            continue
        
        # 将当前节点添加到访问集合中
        visited.add(current_vertex)

        # 如果节点是终点，则返回结果
        if current_vertex == end:
            path = []
            while previous_vertices[current_vertex] is not None:
                path.append(current_vertex)
                current_vertex = previous_vertices[current_vertex]
            path.append(start)
            path.reverse()
            return path, distances[end]
        
        # 更新相邻节点距离和前驱节点信息
        for neighbor, weight in graph[current_vertex].items():
            if neighbor in visited:
                continue
            new_distance = current_distance + weight
            if new_distance < distances[neighbor]:
                distances[neighbor] = new_distance
                previous_vertices[neighbor] = current_vertex
                heapq.heappush(heap, (new_distance, neighbor))

    # 如果未找到终点，则返回None
    return None, None

其中，graph表示图的邻接矩阵，start表示起始节点，end表示终止节点。函数返回从起点到终点的最短路径和距离。