我有一个包含自循环的 NetworkX MultiDiGraph。根据 documentation ,这是 MultiDiGraph 的有效属性。
但是,当我尝试使用 MG.remove_edges_from(MG.selfloop_edges())
从 MultiDiGraph 中删除 selfloops 时,会生成以下警告:
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-13-ff3391f2296f> in <module>()
1 # remove selfloop edges from the graph
----> 2 MG.remove_edges_from(MG.selfloop_edges())
~/Program_Files/miniconda3/envs/py36/lib/python3.6/site-packages/networkx/classes/multigraph.py in remove_edges_from(self, ebunch)
603 []
604 """
--> 605 for e in ebunch:
606 try:
607 self.remove_edge(*e[:3])
~/Program_Files/miniconda3/envs/py36/lib/python3.6/site-packages/networkx/classes/function.py in <genexpr>(.0)
1154 return ((n, n)
1155 for n, nbrs in G.adj.items()
-> 1156 if n in nbrs for d in nbrs[n].values())
1157 else:
1158 return ((n, n) for n, nbrs in G.adj.items() if n in nbrs)
~/Program_Files/miniconda3/envs/py36/lib/python3.6/_collections_abc.py in __iter__(self)
759
760 def __iter__(self):
--> 761 for key in self._mapping:
762 yield self._mapping[key]
763
RuntimeError: dictionary changed size during iteration
从 MultiDiGraph 中删除自循环的方式是否遗漏了什么,或者这是 NetworkX 的错误?
演示意外错误的可重现示例:
import networkx as nx
# create an empty MultiDiGraph
MG = nx.MultiDiGraph()
# add some edges to the graph
MG.add_edges_from([(1, 2), (2, 3), (3, 1), (1, 2), (2, 1), (2, 2)])
# check the edges in the graph
MG.edges()
# remove selfloop edges from the graph
MG.remove_edges_from(MG.selfloop_edges())
此方法与 DiGraph 一起按预期工作,如下所示:
# create an empty MultiDiGraph
G = nx.DiGraph()
# add some edges to the graph
G.add_edges_from([(1, 2), (2, 3), (3, 1), (1, 2), (2, 1), (2, 2)])
# check the edges in the graph
G.edges
OutEdgeView([(1, 2), (2, 3), (2, 1), (2, 2), (3, 1)])
# remove selfloop edges from the graph
G.remove_edges_from(G.selfloop_edges())
# check the edges in the graph
G.edges()
OutEdgeView([(1, 2), (2, 3), (2, 1), (3, 1)])
最佳答案
问题是 MG.selfloop_edges()
是图中自循环边上的迭代器(更准确地说是生成器),通过删除边,您在迭代过程中更改了迭代器的边。
根据 documentation :
这意味着 ebunch
参数应该是一个容器,而 MG.selfloop_edges()
返回一个生成器。您可以阅读有关两个 here 之间差异的更多信息。
这个问题可以通过将 list(MG.selfloop_edges())
传递给 MG.remove_edges_from
来解决(而不是直接传递 MG.selfloop_edges()
)。
关于python - 从 NetworkX MultiDiGraph 中删除 selfloops 会导致运行时错误,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/52528417/