请用Python写一段迪杰斯特拉算法

以下是Python实现的迪杰斯特拉算法：

import heapq

def dijkstra(graph, start):
    distances = {node: float('inf') for node in graph}
    distances[start] = 0
    pq = [(0, start)]
    while pq:
        current_distance, current_node = heapq.heappop(pq)
        if current_distance > distances[current_node]:
            continue
        for neighbor, weight in graph[current_node].items():
            distance = current_distance + weight
            if distance < distances[neighbor]:
                distances[neighbor] = distance
                heapq.heappush(pq, (distance, neighbor))
    return distances

其中，`graph`是一个字典，表示图的邻接表，`start`是起点。函数返回一个字典，表示从起点到各个节点的最短距离。