使用Matplotlib的网络图，节点组周围有圆圈

import matplotlib.pyplot as plt
import networkx as nx

# 创建一个空的有向图
G = nx.DiGraph()

# 添加节点
G.add_node("节点1")
G.add_node("节点2")
G.add_node("节点3")

# 添加边
G.add_edge("节点1", "节点2")
G.add_edge("节点2", "节点3")
G.add_edge("节点3", "节点1")

# 绘制网络图
pos = nx.spring_layout(G)  # 设置节点位置
nx.draw_networkx_nodes(G, pos, node_color='r', node_size=500)  # 绘制节点
nx.draw_networkx_edges(G, pos, arrows=True)  # 绘制边
nx.draw_networkx_labels(G, pos)  # 绘制节点标签

# 添加圆圈
circle = plt.Circle((0.5, 0.5), 0.3, color='blue', fill=False)
plt.gca().add_patch(circle)

# 显示图形
plt.axis('off')
plt.show()