从 Python 架子检索前后对象更改的哈希值

Question

问题

我生成一个 chimera 图，它基本上是一个 dwave_networkx 对象。 dwave_networkx 继承自 networkx 图 class。我把它存放在 Python 架子上。原图的hash和从架子上找回来的hash不一样，想不通是什么原因。我要求两者相同。

代码

import dwave_networkx as dnx
import shelve


def generate_graph(N):

    graph = dnx.chimera_graph(1, N, 4)
    graph_id = ""
   
    for node in graph.nodes:
        graph.nodes[node]['weight'] = _get_node_weight() # A function that returns a random number
    for edge in graph.edges:
        graph.edges[edge]['weight'] = _get_edge_weight() # A function that returns a random number
    
    graph_id = str(hash(graph))
    return graph, graph_id

shelf = shelve.open("graphs.shelf")
ids = []

for i in range(10):
    graph, id = generate_graph(5)
    ids.append(id)
    shelf[id] = {"graph": graph}

for i in ids:
    print(i, hash(shelf[i]["graph"])

# The two values in each row turn out to be different!

shelf.close()

这可能是什么原因？

Answer 1

可能是因为 shelf 对象基本上是在创建原始图形的副本。看这个例子：

shelf = shelve.open("dummy.shelf")

# List are mutable, just like the Graphs
x = [1, 2, 3]

# Add the the list to shelf
shelf["1"] = x

print(id(x), id(shelf["1"]))
# 5314942976 5314799232

shelf.close()

如您所见，创建了原始列表的副本并将其添加到货架（类似于图形发生的情况，因为它们是可变的类）。您可以查看 implementation here 了解更多信息。

参考文献：

Python Shelve

从 Python 架子检索前后对象更改的哈希值

Hash of object changes before and after retrieving from Python shelf

python-3.x

dictionary

hash

persistence

networkx

问题

代码