NetworkX中MultiDiGraph创建求助：双向边未正常显示

你的代码核心问题是：创建MultiDiGraph实例后，又通过nx.from_edgelist(edgelist)重新给变量G赋值，而这个方法默认生成的是无向Graph对象——这会让(2,3)和(3,2)被判定为同一条边，绘图自然只显示一条，且你最初创建的MultiDiGraph会被完全覆盖，根本没发挥作用。

以下是两种修正方案：

方案一：直接向MultiDiGraph添加边 #

import networkx as nx
import matplotlib.pyplot as plt

# 创建MultiDiGraph实例
G = nx.MultiDiGraph()

# 添加节点与边
G.add_nodes_from(range(1, 11))
edgelist = [(1, 2), (2, 3), (3, 2), (3, 9), (9, 4), (4, 5), (5, 7), (7, 6), (6, 4), (7, 8), (7, 10), (10, 11), (11, 5)]
G.add_edges_from(edgelist)

# 调整布局避免边重叠，k值越小节点间距越大
pos = nx.spring_layout(G, k=0.3)
nx.draw_networkx(G,
                 pos=pos,
                 with_labels=True,
                 arrows=True,
                 arrowstyle='->',
                 node_size=100,
                 node_color='yellow',
                 edge_color='black',
                 width=3,
                 arrowsize=10)

plt.show()

方案二：用from_edgelist直接创建MultiDiGraph #

import networkx as nx
import matplotlib.pyplot as plt

edgelist = [(1, 2), (2, 3), (3, 2), (3, 9), (9, 4), (4, 5), (5, 7), (7, 6), (6, 4), (7, 8), (7, 10), (10, 11), (11, 5)]
# 指定create_using参数，直接生成MultiDiGraph
G = nx.from_edgelist(edgelist, create_using=nx.MultiDiGraph())

# 补充添加未在边列表中出现的节点
G.add_nodes_from(range(1, 11))

# 绘制图形
pos = nx.spring_layout(G, k=0.3)
nx.draw_networkx(G,
                 pos=pos,
                 with_labels=True,
                 arrows=True,
                 arrowstyle='->',
                 node_size=100,
                 node_color='yellow',
                 edge_color='black',
                 width=3,
                 arrowsize=10)

plt.show()

额外优化：区分双向边 #

如果想更清晰地区分(2,3)和(3,2)，可以给两条边设置不同颜色单独绘制：

# 先绘制节点和标签
nx.draw_networkx_nodes(G, pos, node_size=100, node_color='yellow')
nx.draw_networkx_labels(G, pos)

# 单独绘制双向边
nx.draw_networkx_edges(G, pos, edgelist=[(2,3)], edge_color='red', width=3, arrows=True, arrowsize=10)
nx.draw_networkx_edges(G, pos, edgelist=[(3,2)], edge_color='blue', width=3, arrows=True, arrowsize=10)

# 绘制其余边
other_edges = [e for e in edgelist if e not in [(2,3), (3,2)]]
nx.draw_networkx_edges(G, pos, edgelist=other_edges, edge_color='black', width=3, arrows=True, arrowsize=10)

plt.show()

内容的提问来源于stack exchange，提问作者runiedKing