How to draw properly networkx graphs

Question

I got this code which allows me to draw a graph like the posted below

import networkx as nx
import pylab as plt
from networkx.drawing.nx_agraph import graphviz_layout


G = nx.DiGraph()
G.add_node(1,level=1)
G.add_node(2,level=2)
G.add_node(3,level=2)
G.add_node(4,level=3)

G.add_edge(1,2)
G.add_edge(1,3)
G.add_edge(2,4)

nx.draw(G, pos=graphviz_layout(G), node_size=1600, cmap=plt.cm.Blues,
        node_color=range(len(G)),
        prog='dot')
plt.show()

Question is, how could i draw the graph with nodes which:

• Use white background color
• Have labels inside
• Have directed arrows
• Optionally the arrows show a certain weight
• Are arranged nicely either automatically or manually

Something similar to the below image

As you can see in that image, nodes are aligned really nicely

Answer 1

Since you have Graphviz you can use that to make nice drawings and control the elements of the drawing. The 'dot' layout engine does a great job of positioning digraphs like the one in your example. For example

import networkx as nx
import pylab as plt
from networkx.drawing.nx_agraph import graphviz_layout, to_agraph
import pygraphviz as pgv

G = nx.DiGraph()
G.add_node("A",rank=0)
G.add_nodes_from(['B','C','D'],style='filled',fillcolor='red')
G.add_nodes_from(['D','F','G'])
G.add_nodes_from(['H'],label='target')
G.add_edge('A','B',arrowsize=2.0)
G.add_edge('A','C',penwidth=2.0)
G.add_edge('A','D')
G.add_edges_from([('B','E'),('B','F')],color='blue')
G.add_edges_from([('C','E'),('C','G')])
G.add_edges_from([('D','F'),('D','G')])
G.add_edges_from([('E','H'),('F','H'),('G','H')])

# set defaults
G.graph['graph']={'rankdir':'TD'}
G.graph['node']={'shape':'circle'}
G.graph['edges']={'arrowsize':'4.0'}

A = to_agraph(G)
print(A)
A.layout('dot')
A.draw('abcd.png')

Produces the output

strict digraph {
    graph [rankdir=TD];
    node [label="\N",
        shape=circle
    ];
    A    [rank=0];
    C    [fillcolor=red,
        style=filled];
    A -> C   [penwidth=2.0];
    B    [fillcolor=red,
        style=filled];
    A -> B   [arrowsize=2.0];
    D    [fillcolor=red,
        style=filled];
    A -> D;
    C -> E;
    C -> G;
    B -> E   [color=blue];
    B -> F   [color=blue];
    D -> G;
    D -> F;
    H    [label=target];
    E -> H;
    G -> H;
    F -> H;
}

which is rendered by dot as

You can read about the adjustable drawing parameters at http://www.graphviz.org/doc/info/attrs.html