Problems printing weight in a NetworkX graph

问题

I'm reading an edgelist using networkX. The edgelist contains entries of the form:

1; 2; 3

2; 3; 5

3; 1; 4

where 3rd column is the weight. When I plot this, it displays the weight 3 as:

{'weight': 3}

instead of just 3. Ultimately I want to be able to perform operations using the weight (e.g. calculated highest weight, display only the edges which have a weight:

'x', etc.,

Here is the minimal working code:

import networkx as nx
import pylab as plt

G=nx.Graph()
G=nx.read_edgelist('sample_with_weights.edges', data= (('weight',int),))
pos = nx.spring_layout(G)
nx.draw_networkx(G, pos=pos)
nx.draw_networkx_edge_labels(G, pos=pos)
nx.draw_networkx_edges(G,pos,width=4, edge_color='g', edge_labels = 'weight', arrows=False)
plt.show()

回答1:

Some observations regarding the existing code:

That read_edgelist is not going to work well with that edge list file because the 'special' delimiter ; has not been specified.
The edge labels should be specified in the draw_networkx_edge_labels function call, rather than the draw_networkx_edges; and also
The edge_labels is a dictionary keyed by edge two-tuple of text labels (default=None). Only labels for the keys in the dictionary are drawn. (from the documentation)

So, the general idea is to use the edge_labels to selectively print edge weights. Please see inline comments below:

import networkx as nx
import pylab as plt

G=nx.Graph()
#Please note the use of the delimiter parameter below
G=nx.read_edgelist('test.edges', data= (('weight',int),), delimiter=";")
pos = nx.spring_layout(G)

#Here we go, essentially, build a dictionary where the key is tuple
#denoting an edge between two nodes and the value of it is the label for
#that edge. While constructing the dictionary, do some simple processing
#as well. In this case, just print the labels that have a weight less
#than or equal to 3. Variations to the way new_labels is constructed
#produce different results.
new_labels = dict(map(lambda x:((x[0],x[1]), str(x[2]['weight'] if x[2]['weight']<=3 else "") ), G.edges(data = True)))

nx.draw_networkx(G, pos=pos)

#Please note use of edge_labels below.
nx.draw_networkx_edge_labels(G, pos=pos, edge_labels = new_labels)
nx.draw_networkx_edges(G,pos,width=4, edge_color='g', arrows=False)

plt.show()

Given a data file test.edges that looks like...