我正在python中实现统一成本搜索功能，但当我尝试运行代码时，会出现一个错误，显示"TypeError:"Graph"对象不可下标；。下面是我的代码。我已经将Queue和Graph导入到我的主函数中。我已经研究了一段时间，但找不到问题所在，如果有人能帮忙的话？谢谢：
from graph import Graph
from queue import PriorityQueue
def uniform_cost_search(graph, start_node, goal_node):
queue=PriorityQueue()
queue.insert([start_node],0)
while not queue.is_empty():
node=queue.remove()
current=node[1][len(node[1])-1]
if goal_node in node[1]:
print("Path found:"+str(node[1])+",Cost="+str(node[0]))
break
cost=node[0]
for i in graph[current]:# This line is causing the error
temp=node[1][:]
temp.append(i)
queue.insert(temp,cost+graph[current][i])
if __name__ == "__main__":
# Defining Graph
graph = Graph()
# setting up nodes and neighbours
graph.edges = {
'A': set(['B', 'D']),
'B': set(['A','E','C']),
'C': set(['B', 'E', 'G']),
'D': set(['A','E','F']),
'E': set(['B', 'C', 'D', 'G']),
'F': set(['D','G']),
'G': set(['F','E','C'])
}
# setting up connection costs
graph.weights = {
'AB': 5, 'AD': 3,
'BA': 5, 'BE': 4, 'BC': 1,
'CB': 1, 'CE': 6, 'CG': 8,
'DA': 3, 'DE': 2, 'DF': 2,
'EB': 4, 'EC': 6, 'ED': 2, 'EG': 4,
'FD': 2, 'FG': 3,
'GF': 3, 'GE': 4, 'GC': 8
}
uniform_cost_search(graph, 'A', 'G')
"""
the above statement should result in the following:
Shortest Path: A,D,F,G
Cost: 8
"""
图形代码：
class Graph:
def __init__(self):
self.edges = {} # dictionary of edges NODE: NEIGHBOURS
self.weights = {} # dictionary of NODES and their COSTS
def neighbours(self, node):
"""
The function returns the neighbour of the node passed to it,
which is essentially the value of the key in the edges dictionary.
:params node: (string) a node in the graph
:return: (list) neighbouring nodes
"""
return self.edges[node]
def get_cost(self, from_node, to_node):
"""
Gets the cost of a connection between adjacent nodes.
:params from_node: (string) starting node
:params to_node: (string) ending node
:return: (int)
"""
return self.weights[(from_node + to_node)]
if __name__ == "__main__":
# testing out the graph class
graph = Graph()
# setting up nodes and neighbours
graph.edges = {
'A': set(['B', 'D']),
'B': set(['A','E','C']),
'C': set(['B', 'E', 'G']),
'D': set(['A','E','F']),
'E': set(['B', 'C', 'D', 'G']),
'F': set(['D','G']),
'G': set(['F','E','C'])
}
# setting up connection costs
graph.weights = {
'AB': 5, 'AD': 3,
'BA': 5, 'BE': 4, 'BC': 1,
'CB': 1, 'CE': 6, 'CG': 8,
'DA': 3, 'DE': 2, 'DF': 2,
'EB': 4, 'EC': 6, 'ED': 2, 'EG': 4,
'FD': 2, 'FG': 3,
'GF': 3, 'GE': 4, 'GC': 8
}
print("Neighbours of Node A are:",graph.neighbours('A'))
print("Cost going from A to D is:", graph.get_cost('A','D'))
队列代码：
import heapq
class PriorityQueue:
def __init__(self):
self.__queue = []
self.__index = 0
def insert(self, item, priority):
"""
The function takes in the item and its priority, wraps it up in a tuple and
inserts it in the heap.
:params item: item to be inserted into the queue
:params priority: the priority of the item to be inserted
:return: None
"""
heapq.heappush(self.__queue, (priority, self.__index, item))
self.__index += 1
def remove(self):
"""
The functions removes the lowest priority item from the priority queue (via heaps)
and returns the item along with the cost of it.
:return : the item with the lowest priority
"""
temp = heapq.heappop(self.__queue)
cost = temp[0]
item = temp[-1]
return cost, item
def is_empty(self):
"""
Checks whether the queue is empty or not.
:returns: (Boolean)
"""
return len(self.__queue) == 0
if __name__ == "__main__":
# testing priority queue
queue = PriorityQueue()
queue.insert('e', 9)
queue.insert('a', 2)
queue.insert('h', 13)
queue.insert('c', 11)
print(queue.remove())
print(queue.remove())
print(queue.remove())
要实现可下标，对象类型必须继承自另一个可下标的类型(如dict(，或者实现特殊方法__getitem__()。
Graph不执行这两种操作，因此它不是可下标的对象类型。