python-3.x - Networkx 未在有向图中绘制箭头

Question

我有一个 5 节点有向网络，我想使用 networkx 以图形方式表示它。节点应该以这种方式连接:

• 每个节点都用虚线相互连接
• 事件连接从文件中读取并用实心黑色箭头表示
• 进出运行代码的节点(在本例中为节点 1)的事件连接应为红色。

代码可以满足我的要求，但出于某种原因，即使我在想要制作红色边缘时指定了 arrow=True，箭头也不会出现。由于某种原因，它似乎忽略了我在 edge_color 之后指定的每个选项。

我注意到当我在所有节点之间绘制边时，如果我没有指定 arrows=False 它会忽略 style='dashed', alpha=0.5 和只是画一条灰色实线。这与问题有什么关系吗？

这是我的代码，有问题的部分用注释注释:

import networkx as nx
import matplotlib.pyplot as plt

class Graph(nx.DiGraph):
    def __init__(self, *args, **kwargs):
        self.nodeNum = 1
        self.pos = {'1': (0, 10),
                    '2': (10, 3),
                    '3': (6, -8),
                    '4': (-6, -8),
                    '5': (-10, 3)}
        self.allConns = []
        for i in range(5):
            for j in range(i, 5):
                self.allConns.append((str(i+1), str(j+1)))
        super().__init__(*args, **kwargs)

    def read_connections(self):
        filename = 'PATH/TO/FILE'
        with open(filename) as f:
            self.connList = []
            self.nodeConns = []
            for line in f:
                if line[-2] == '1':
                    self.connList.append((str(line[0]), str(line[1])))
                    if line[0] == self.nodeNum or line[1] == self.nodeNum:
                        self.nodeConns.append((str(line[0]), str(line[1])))
                    else:
                        pass
                else:
                    pass

    def generate_graph(self):
        self.read_connections()
        self.add_nodes_from(self.pos.keys())
        self.add_edges_from(self.connList)
        

    def draw_graph(self, fig=None, ax=None, show=False):
        if fig == None:
            fig = plt.figure()
        if ax == None:
            ax = fig.add_subplot(111)
        ax.axis('off')
        options = {'node_color': 'cyan',
                   'node_size': 1500,
                   'width': 2,
                   'arrowstyle': '-|>',
                   'arrowsize': 14,
                   'font_size': 20
                   }
        
        # This works, but if I do not specify arrows=False it draws solid lines with no transparency
        nx.draw_networkx_edges(self, self.pos, ax=ax, edgelist=self.allConns, edge_color='grey',
                               style='dashed', alpha=0.5, arrows=False)  

        # This is the main part which works. It connects the nodes from the file with black arrows
        nx.draw_networkx(self, self.pos, arrows=True, ax=ax, **options)

        # This is the part that gives me problems. It seems to ignore every option after edge_color
        nx.draw_networkx_edges(self, self.pos, ax=ax, edgelist=self.nodeConns, edge_color='r',
                               style='solid',alpha=1,
                               arrows=True, width=3, arrowsize=14, arrowstyle='-|>')
        nx.draw_networkx_nodes(self, self.pos, ax=ax, nodelist=[self.nodeNum], node_color='r',
                               node_size=1500)

        fig.tight_layout()
        if show == True:
            fig.show()

if __name__ == '__main__':
    graph = Graph()
    graph.generate_graph()
    graph.draw_graph(show=True)

以及结果的示例。请注意红色边缘没有箭头。

Answer 1

我很确定绘制了箭头，但根本看不到，因为您随后默认绘制了具有更大节点大小的节点。将 node_size 赋给 draw_networkx_edges应该可以解决你的问题

nx.draw_networkx_edges(self, self.pos, ax=ax, 
edgelist=self.nodeConns, edge_color='r', 
style='solid',alpha=1, arrows=True, width=3, 
arrowsize=14, arrowstyle='-|>',
node_size=1500,
)

还有 draw_networkx_edges 的文档包含以下注释

For directed graphs, arrows are drawn at the head end. (...) Be sure to include node_size as a keyword argument; arrows are drawn considering the size of nodes