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我正在使用networkx包Python 2.7 Enthought distribution来计算海港网络之间的最短路径。使用 计算距离可以正常工作dijkstra_path_length，但我还需要知道它使用了什么路线dijkstra_path（顺便说一句，我认为如果我先计算路径，然后从路径计算长度而不是在相同的数据上运行 Dijkstra 算法两次）。但是路径功能失败了，说list indices must be integers, not str。

这是产生错误的代码。谁能告诉我我做错了什么？

import networkx as nx

# Create graph
network_graph = nx.Graph()
f_routes = open('routes-list.txt', 'rb')
# Assign list items to variables
for line in f_routes:
    route_list = line.split(",")
    orig = route_list[0]
    dest = route_list[1]
    distance = float(route_list[2])
    # Add route as an edge to the graph
    network_graph.add_edge(orig, dest, distance=(distance))

# Loop through all destination and origin pairs
for destination in network_graph:
    for origin in network_graph:
        # This line works
        length = nx.dijkstra_path_length(network_graph, origin, destination, "distance")
        # This line fails
        path = nx.dijkstra_path(network_graph, origin, destination, "distance")

我在回溯中得到以下信息。

Traceback (most recent call last):
  File "C:\Users\jamie.bull\workspace\Shipping\src\shortest_path.py", line 67, in <module>
    path = nx.dijkstra_path(network_graph, origin, destination, "distance")
  File "C:\Enthought\Python27\lib\site-packages\networkx\algorithms\shortest_paths\weighted.py", line 74, in dijkstra_path
    return path[target]
TypeError: list indices must be integers, not str
4

1 回答 1

17

nx.dijkstra_path尝试一下，当源节点和目标节点相同时，似乎会引发一个误导性异常：

>>> import networkx as nx
>>> g = nx.Graph()
>>> g.add_edge('a', 'b', distance=0.3)
>>> g.add_edge('a', 'c', distance=0.7)
>>> nx.dijkstra_path_length(g, 'b', 'c', 'distance')
1.0
>>> nx.dijkstra_path(g, 'b', 'c', 'distance')
['b', 'a', 'c']
>>> nx.dijkstra_path_length(g, 'b', 'b', 'distance')
0
>>> nx.dijkstra_path(g, 'b', 'b', 'distance')
Traceback (most recent call last):
  File "<pyshell#7>", line 1, in <module>
    nx.dijkstra_path(g, 'b', 'b', 'distance')
  File "C:\Users\barberm\AppData\Roaming\Python\Python27\site-packages\networkx\algorithms\shortest_paths\weighted.py", line 74, in dijkstra_path
    return path[target]
TypeError: list indices must be integers, not str

所以只要显式测试destination和是否origin相同，相同时分别处理。

于 2013-01-16T09:08:38.000 回答