generate a random tree in .dot format (for graphviz to process)

gen-dot-tree.py

#!/usr/bin/python

import argparse, numpy as np

def gen_tree(depth, id, branch):
    label = id if args.label is None else args.label
    print '    '*depth + id + '[label="' + label + '"];'
    if depth >= args.depth:
        return
    nchild = np.random.poisson(branch)
    edge_cmd = '    '*depth + id + '->{'
    for i in range(0, nchild):
        cid = id+chr(65+i)
        edge_cmd += ' ' + cid
        gen_tree(depth+1, cid, branch*args.decay)
    print edge_cmd + ' }'

parser = argparse.ArgumentParser(description='generate a tree in .dot format (for graphviz)',formatter_class=argparse.ArgumentDefaultsHelpFormatter)
parser.add_argument('-d', '--depth', type=int, default='5',
    help='max depth')
parser.add_argument('-b', '--branch', type=float, default=3.0,
    help='expected number of branches for 1st level')
parser.add_argument('-y', '--decay', type=float, default=0.6,
    help='branch decay factor')
parser.add_argument('-R', '--root-label', type=str, default='X',
    help='node label')
parser.add_argument('-L', '--label', type=str,
    help='node label')
args = parser.parse_args()

print '''
// twopi -Tsvg xxx.dot -o xxx.svg
digraph "" {
    overlap = scale;
'''
gen_tree(1, args.root_label, args.branch)
print '}'