这段代码报错： KeyError: 'id'

抱歉，这是我的疏忽。在 `G.add_edge` 函数中需要添加 `id` 属性，但是不是所有边都有 `id` 属性，所以有些边没有 `id` 属性，导致 `KeyError`。为了解决这个问题，需要在添加边时先判断该边是否有 `id` 属性，如果有就添加，没有就不添加。修改后的代码如下：

import pandas as pd 
import numpy as np 
import networkx as nx 
import matplotlib.pyplot as plt 

df = pd.read_excel(r"C:\Users\li'yi'jie\Desktop\运筹学网络规划数据.xlsx") 
edges = [] 
for i in range(len(df)): 
    edge = { 
        "tail": df.loc[i, "边的尾节点"], 
        "head": df.loc[i, "边的头节点"], 
        "length": df.loc[i, "长度"], 
        "capacity": df.loc[i, "容量"] 
    } 
    if "边的编号" in df.columns: 
        edge["id"] = df.loc[i, "边的编号"] 
    edges.append(edge) 

plt.figure(figsize=(15,15)) 
G = nx.DiGraph() 
for edge in edges: 
    if "id" in edge: 
        G.add_edge(edge["tail"], edge["head"], weight=edge["length"], id=edge["id"]) 
    else: 
        G.add_edge(edge["tail"], edge["head"], weight=edge["length"]) 
pos = nx.spring_layout(G) 
nx.draw(G, pos, with_labels=True) 
labels = nx.get_edge_attributes(G, "weight") 
nx.draw_networkx_edge_labels(G, pos, edge_labels=labels) 
plt.show() 

all_pairs = dict(nx.all_pairs_dijkstra_path_length(G)) 
rows = [] 
for start_node, dist_dict in all_pairs.items(): 
    for end_node, dist in dist_dict.items(): 
        path_edges = [] 
        if start_node != end_node: 
            path = nx.shortest_path(G, start_node, end_node) 
            for i in range(len(path)-1): 
                tail = path[i] 
                head = path[i+1] 
                if "id" in G[tail][head]: 
                    path_edges.append(G[tail][head]['id']) 
            rows.append({'起始节点': start_node, '终止节点': end_node, '最短路径长度': dist, '经过边的编号': path_edges}) 

df_result = pd.DataFrame(rows) 
df_result.to_excel('all_pairs.xlsx', index=False)

这样修改后，就可以在添加边时判断边是否有 `id` 属性，从而避免 `KeyError` 异常了。