How to add node and edge attributes

Hi

Is there a way to add node and edge attributes. Not successful via networkx. Does pydot give an option?

Below is the code, with not working section commented.

#  NETWORX TO PYDOT TO GRAPHVIZ MODULE
P = nx.nx_pydot.to_pydot(G)

# before sending to neato, fix the pos values
# 1. A [pos="(21.31227, 46.18656)"]; should become A [pos="21.31227, 46.18656!"];
P1 = str(P).replace('"(', '"').replace(')"','!"')
print(P1)
M = Source(P1, engine='neato',format='png')

# NOT WORKING START #-------------------
# M.attr(overlap='compress')
# M.attr(sep='3')
# M.attr('edge', fontsize='9', color='grey', fontcolor='#7c7c7c')
# M.attr('node', shape='box', width='0.1', height='0.1', style='filled', fontname="Arial", fontsize='10', fixedsize='true', color="#666666")
# NOT WORKING END #---------------------

M.render('test1', view=True)  

[peternowee]

Hmm, yes, I see. I do not know NetworkX that well, but looking at the source code, it does seem to try to set some defaults at the start of the export:

    name = N.name
    graph_defaults = N.graph.get("graph", {})
    if name == "":
        P = pydot.Dot("", graph_type=graph_type, strict=strict, **graph_defaults)
    else:
        P = pydot.Dot(
            f'"{name}"', graph_type=graph_type, strict=strict, **graph_defaults
        )
    try:
        P.set_node_defaults(**N.graph["node"])
    except KeyError:
        pass
    try:
        P.set_edge_defaults(**N.graph["edge"])
    except KeyError:
        pass

From: https://github.com/networkx/networkx/blob/networkx-2.6.3/networkx/drawing/nx_pydot.py#L197-L212

Where N is the NetworkX graph, so if we can set N.graph["graph"], N.graph["node"], and N.graph["edge"] before calling nx.drawing.nx_pydot.to_pydot(), NetworkX should include them as defaults in the pydot graph. For example:

import networkx as nx
import pydot
G = nx.Graph()
G.graph["node"] = {"style": "filled", "fillcolor": "blue"}
G.add_node("a")
graph = nx.drawing.nx_pydot.to_pydot(G)
print(graph)

Output:

strict graph  {
node [fillcolor=blue, style=filled];
a;
}

This is what you mean, right?

[peternowee]

For posterity’s sake, showing some different ways:

import pydot
G = pydot.Dot('G', overlap='compress')
G.set_sep('3')
G.set_edge_defaults(fontsize='9', color='grey', fontcolor='#7c7c7c')
G.set_node_defaults(shape='box', width='0.1', height='0.1', style='filled', fontname="Arial", fontsize='10', fixedsize='true', color="#666666")
N = pydot.Node('N')
G.add_node(N)
O = pydot.Node('O', width='0.5')
O.set_height('0.8')
G.add_node(O)
print(G)

Output:

digraph G {
overlap=compress;
sep=3;
edge [color=grey, fontcolor="#7c7c7c", fontsize=9];
node [color="#666666", fixedsize=true, fontname=Arial, fontsize=10, height="0.1", shape=box, style=filled, width="0.1"];
N;
O [height="0.8", width="0.5"];
}

Alternatively, you can access G.obj_dict['attributes'] directly, but I assume that is discouraged.