networkx - change color/width according to edge attributes - inconsistent result

Question

I managed to produce the graph correctly, but with some more testing noted inconsistent result for the following two different line of codes:

colors = [h.edg         


        

Answer 1

Dictionaries are the underlying data structure used for NetworkX graphs, and as of Python 3.7+ they maintain insertion order. This means that we can safely use nx.get_edge_attributes to retrieve edge attributes since we are guaranteed to have the same edge order in every run of Graph.edges() (which is internally called by get_edge_attributes).

So when plotting, we can directly set attributes such as edge_color and width from the result returned by get_edge_attributes. Here's an example:

G = nx.Graph()
G.add_edge(0,1,color='r',weight=2)
G.add_edge(1,2,color='g',weight=4)
G.add_edge(2,3,color='b',weight=6)
G.add_edge(3,4,color='y',weight=3)
G.add_edge(4,0,color='m',weight=1)

colors = nx.get_edge_attributes(G,'color').values()
weights = nx.get_edge_attributes(G,'weight').values()

pos = nx.circular_layout(G)
nx.draw(G, pos, 
        edge_color=colors, 
        width=list(weights),
        with_labels=True,
        node_color='lightgreen')

Answer 2

The order of the edges passed to the drawing functions are important. If you don't specify (using the edges keyword) you'll get the default order of G.edges(). It is safest to explicitly give the parameter like this:

import networkx as nx

G = nx.Graph()
G.add_edge(1,2,color='r',weight=2)
G.add_edge(2,3,color='b',weight=4)
G.add_edge(3,4,color='g',weight=6)

pos = nx.circular_layout(G)

edges = G.edges()
colors = [G[u][v]['color'] for u,v in edges]
weights = [G[u][v]['weight'] for u,v in edges]

nx.draw(G, pos, edges=edges, edge_color=colors, width=weights)

This results in an output like this: