GRASS script to convert cost points generated by pgRouting's driving_distance() to polygons of 1/4 mile increments

cost_points_to_poly.py

#!/usr/bin/env python

import os
import atexit
import sys
import subprocess

gisbase = os.environ['GISBASE'] = '/usr/lib/grass64'
gisdbase = os.path.join(os.environ['HOME'], 'grassdata')
location = 'fairfax'
mapset = 'PERMANENT'

sys.path.append(os.path.join(os.environ['GISBASE'], 'etc', 'python'))
from grass.script import core as grass
import grass.script.setup as gsetup

gsetup.init(gisbase, gisdbase, location, mapset)
print grass.gisenv()

def main():
    cost_points_file = '/home/user/points_2283.shp'
    out_file = '/home/user/polys.shp'

    # generate contour polygons
    grass.run_command('v.in.ogr', dsn=cost_points_file, output='cost_points',
                      overwrite=True)
    grass.run_command('g.region', vect='cost_points', rows=512, cols=512)
    grass.run_command('v.surf.rst', input='cost_points', elev='interp',
                      zcolumn='cost', overwrite=True)
    grass.run_command('r.mapcalc', result='int(interp/0.4)')
    grass.run_command('r.to.vect', flags='s', input='result',
                      output='polys', feature='area', overwrite=True)
    grass.run_command('v.out.ogr', input='polys', dsn=out_file, type='area',
                      flags='c')

if __name__ == "__main__":
    main()