python - 如何使用 NetworkX 在加权图中获得最短路径？

Question

我试图在定义为的加权图中获得最短路径

import networkx as nx
import matplotlib.pyplot as plt
g = nx.Graph()
g.add_edge(131,673,weight=673)
g.add_edge(131,201,weight=201)
g.add_edge(673,96,weight=96)
g.add_edge(201,96,weight=96)
nx.draw(g,with_labels=True,with_weight=True)
plt.show()

这样做我使用

nx.shortest_path(g,source=131,target=96)

预期的答案是 131,201,96，因为对于该路径，我的权重总和最少。我得到的是 131,673,96。我尝试改变权重，但 shortest_path显然总是返回最长的路径。到底是怎么回事？

Answer 1

来自 documentation of nx.shortest_path :

shortest_path(G, source=None, target=None, weight=None, method='dijkstra')[source]
Compute shortest paths in the graph.

Parameters
G (NetworkX graph)

source (node, optional) – Starting node for path. If not specified, compute shortest paths for each possible starting node.

target (node, optional) – Ending node for path. If not specified, compute shortest paths to all possible nodes. 

> weight (None or string, optional (default = None)) – If None, every edge has weight/distance/cost 1. If a string, use this edge attribute as the edge weight. Any edge attribute not present defaults to 1.

method (string, optional (default = ‘dijkstra’)) – The algorithm to use to compute the path. Supported options: ‘dijkstra’,

(强调我的)

如果您没有明确声明要找到最短的加权路径(通过指定 weight 参数)，则所有权重都被视为一。

要解决您的问题，请执行以下操作:

print(nx.shortest_path(g,source=131,target=96, weight='weight'))

输出:

[131, 201, 96]