miles.py

#!/usr/bin/env python
"""
An example that shows how to add your own positions to nodes and have graphviz "neato" position the edges

miles_graph() returns an undirected graph over the 128US cities from the database miles_data.txt
"""

from __future__ import absolute_import
from __future__ import unicode_literals
from __future__ import print_function
from __future__ import division

import fileinput
__author__ = """Fish(rahul@heartit.tech)"""

def miles_graph():
    """Return a graph from the data in miles_dat.txt.
    Edges are made between cities that are less then 300 miles apart.
    """
    import math
    import re
    import gzip

    G=pgv.AGraph(name='miles_dat')
    G.node_attr['shape']= 'circle'
    G.node_attr['fixedsize']= 'true'
    G.node_attr['fontsize']= '8'
    G.node_attr['style']= 'filled'
    G.graph_attr['outputorder']='edgesfirst'
    G.graph_attr['label']='miles_dat'
    G.graph_attr['ratio']='1.0'
    G.edge_attr['color']='#1100FF'
    G.edge_attr['style']='setlinewidth(2)'

    cities=[]
    for line in gzip.open("miles_dat.txt.gz", 'rt'):
        if line.startswith("*"):
            continue
        numfind=re.compile("^\d+")

        if(numfind).match(line):
            dist= line.split()
            for d in dist:
                if float(d) < 300:
                    G.add_edge(city, cities[i])
                i=i+1
        else:
            i=1
            (city, coordpop)= line.split("[")
            cities.insert(0, city)
            (coord, pop)= coordpop.split("]")
            (y, x)= coord.split(",")
            G.add_node(city)
            n=G.get_node(city)
            # assign positions, scale to be something reasonable in points
            n.attr['pos']= "%f,%f)"%(-(float(x)-7000)/10.0, (float(y)-2000)/10.0)
            # assign node size, in sqrt of 1,000,000's of people
            d=math.sqrt(float(pop)/1000000.0)
            n.attr['height']="%s"%(d/2)
            n.attr['width']="%s"%(d/2)
            n.attr['fillcolor']="#0000%2x"%(int(d*256))
            n.attr['label']=' '
    
    return G

if __name__ == '__main__':
    import warnings
    import pygraphviz as pgv

    warnings.simplefilter('ignore', RuntimeWarning)

    G=miles_graph()
    print("loaded miles_dat.txt containing 128 cities")

    G.write('miles.dot')
    print('Wrote miles.dot')
    G.draw('miles.png', prog='neato', args='-n2')
    print('wrote miles png')