# 教你一招 | Python实现无向图最短路径

A ——> 0

B ——> 1

C ——> 2

D ——>3

E ——> 4

F ——> 5

G ——> 6

```# -*-coding:utf-8 -*-
class DijkstraExtendPath():
def __init__(self, node_map):
self.node_map = node_map
self.node_length = len(node_map)
self.used_node_list = []
self.collected_node_dict = {}
def __call__(self, from_node, to_node):
self.from_node = from_node
self.to_node = to_node
self._init_dijkstra()
return self._format_path()
def _init_dijkstra(self):
self.used_node_list.append(self.from_node)
self.collected_node_dict[self.from_node] = [0, -1]
for index1, node1 in enumerate(self.node_map[self.from_node]):
if node1:
self.collected_node_dict[index1] = [node1, self.from_node]
self._foreach_dijkstra()
def _foreach_dijkstra(self):
if len(self.used_node_list) == self.node_length - 1:
return
for key, val in self.collected_node_dict.items():  # 遍历已有权值节点
if key not in self.used_node_list and key != to_node:
self.used_node_list.append(key)
else:
continue
for index1, node1 in enumerate(self.node_map[key]):  # 对节点进行遍历
# 如果节点在权值节点中并且权值大于新权值
if node1 and index1 in self.collected_node_dict and self.collected_node_dict[index1][0] > node1 + val[0]:
self.collected_node_dict[index1][0] = node1 + val[0] # 更新权值
self.collected_node_dict[index1][1] = key
elif node1 and index1 not in self.collected_node_dict:
self.collected_node_dict[index1] = [node1 + val[0], key]
self._foreach_dijkstra()
def _format_path(self):
node_list = []
temp_node = self.to_node
node_list.append((temp_node, self.collected_node_dict[temp_node][0]))
while self.collected_node_dict[temp_node][1] != -1:
temp_node = self.collected_node_dict[temp_node][1]
node_list.append((temp_node, self.collected_node_dict[temp_node][0]))
node_list.reverse()
return node_list
def set_node_map(node_map, node, node_list):
for x, y, val in node_list:
node_map[node.index(x)][node.index(y)] = node_map[node.index(y)][node.index(x)] =  val
if __name__ == "__main__":
node = ['A', 'B', 'C', 'D', 'E', 'F', 'G']
node_list = [('A', 'F', 9), ('A', 'B', 10), ('A', 'G', 15), ('B', 'F', 2),
('G', 'F', 3), ('G', 'E', 12), ('G', 'C', 10), ('C', 'E', 1),
('E', 'D', 7)]
node_map = [[0 for val in xrange(len(node))] for val in xrange(len(node))]
set_node_map(node_map, node, node_list)
# A -->; D
from_node = node.index('A')
to_node = node.index('D')
dijkstrapath = DijkstraPath(node_map)
path = dijkstrapath(from_node, to_node)
print path```

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