python - 修复无向 networkx 图中边的排序

Question

在无向 NetworkX 图中，边表示为 Python 元组。他们的订购取决于您要求他们的方式。这是我所指的一个小例子:

import networkx as nx
g = nx.complete_bipartite_graph(2,2)
print(g.edges())
print(g.edges(2))

输出是

[(0, 2), (0, 3), (1, 2), (1, 3)]
[(2, 0), (2, 1)]

有没有办法(不涉及手动排序)避免对边有不同的表示？

Answer 1

我不确定您想要什么，因为在标题中您要求有序边，但在您的示例中您要求边中的有序节点。在我的示例中，我展示了两者的排序。请注意，我使用列表理解来创建新的边列表——原始边列表 (some_edges) 没有改变。

首先如何对边列表中的单个节点元组进行排序。也就是说，边的顺序相同，但其中的节点已排序。

import networkx as nx
g = nx.Graph()
g.add_edges_from([
    (5, 2),
    (2, 1),
    (3, 2),
    (4, 2)
])
some_edges = g.edges(2)
print("Not sorted:  ", some_edges)

print("SORTED")
# sort nodes in edges
some_edges_1 = [tuple(sorted(edge)) for edge in some_edges]
print("Sorted nodes:", some_edges_1)

现在如何对边列表中的边进行排序。

# sort edges in list of edges
some_edges_2 = sorted(some_edges_1)
print("Sorted edges:", some_edges_2)

上面两个代码块的输出:

Not sorted:   [(2, 1), (2, 3), (2, 4), (2, 5)]
SORTED
Sorted nodes: [(1, 2), (2, 3), (2, 4), (2, 5)]
Sorted edges: [(1, 2), (2, 3), (2, 4), (2, 5)]

这里还有一个反向排序的示例，您可以在其中实际看到对单个边进行排序与​​对边列表进行排序之间的区别。

print("Not sorted:  ", some_edges)
print("SORTED REVERSE")
# sort nodes in edges
some_edges_1 = [tuple(sorted(edge, reverse=True)) for edge in some_edges]
print("Sorted nodes:", some_edges_1)
# sort edges in list of edges
some_edges_2 = sorted(some_edges_1, reverse=True)
print("Sorted edges:", some_edges_2)

输出:

Not sorted:   [(2, 1), (2, 3), (2, 4), (2, 5)]
SORTED REVERSE
Sorted nodes: [(2, 1), (3, 2), (4, 2), (5, 2)]
Sorted edges: [(5, 2), (4, 2), (3, 2), (2, 1)]