[英]__iter__ and __getitem__ method in Python
class Graph:
def __init__(self, Nodes, is_directed = False):
self.nodes = Nodes
self.adj_list = {}
self.is_directed = is_directed
for node in self.nodes:
self.adj_list[node] = {}
def add_edge(self, u, v, w):
self.adj_list[u][v] = w
if not self.is_directed:
self.adj_list[v][u] = w
def __len__(self):
return len(nodes)
def __getitem__(self,node):
return self.adj_list[node]
def __iter__(self):
return iter(self.adj_list)
def degree(self,node):
'''Total number of edges coming out a given node'''
return len(self.adj_list[node])
def print_adj_list(self):
for node in self.nodes:
print(node, "->", self.adj_list[node])
all_edges = [
("A","B", 5),("A","C", 4),("B","D", 6),("C","D", 8),
("C","E", 6),("D","E",7)
]
nodes = ["A","B","C","D","E"]
graph1 = Graph(nodes)
for u,v,w in all_edges:
graph1.add_edge(u,v,w)
Graph printed:图表打印:
A -> {'B': 5, 'C': 4}
B -> {'A': 5, 'D': 6}
C -> {'A': 4, 'D': 8, 'E': 6}
D -> {'B': 6, 'C': 8, 'E': 7}
E -> {'C': 6, 'D': 7}
I am trying to iterate through my class object Graph1 and return the key:value pair inside my nested dictionary.我正在尝试遍历我的 class object Graph1 并返回嵌套字典中的键:值对。
I access the nodes我访问节点
for vertex in graph1:
print(vertex)
Which returns:返回:
A
B
C
D
E
But once I try and access the values inside the nested dictionary I cannot:但是,一旦我尝试访问嵌套字典中的值,我就不能:
for edge, weight in graph1["A"]:
print("Edge:", edge, "Weight:", weight)
ValueError: not enough values to unpack (expected 2, got 1)
I am trying to return我正在尝试返回
Edge: B
Weight: 5
Edge: C
Weight: 4
I believe it has something to do with either my iter or getitem method.我相信这与我的iter或getitem方法有关。
for edge, weight in graph1["A"].items(): print("Edge:", edge, "Weight:", weight)对于边,graph1["A"].items() 中的权重: print("Edge:", edge, "Weight:", weight)
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