A Python script that prints the distance between an origin and multiple destinations

computeDistances.py

#!/usr/bin/env python

from optparse import OptionParser
import csv
import json
import StringIO
import sys
import urllib

# Print the distance between an origin and multiple destinations.
def main(cmdline=None):
    parser = make_parser()

    opts, args = parser.parse_args(cmdline)

    # Read the CSV file into a %-encoded string and a string array
    origin = ""
    destinations = []
    with open(args[0], 'rb') as csvfile:
      reader = csv.reader(csvfile)
      for row in reader:
        if reader.line_num == 1:
          origin = urllib.quote(row[0])
        destinations.append(urllib.quote(row[1]))

    # Call Google Maps -- Distance Matrix API and get back JSON result
    jsonResult = urllib.urlopen(
      "http://maps.googleapis.com/maps/api/distancematrix/json?origins=" +
      origin + "&destinations=" + '|'.join(destinations) +
      "&sensor=false&units=imperial").read()

    # Parse JSON result to get the distances in miles
    result = json.loads(jsonResult)
    
    # We have only one row (origin) but several destinations (columns)
    distances = []
    for column in result['rows'][0]['elements']:
      distances.append(column['distance']['value'] / 1609.34) # m/mile

    # Print a CSV result with a third column -- distances in miles    
    output = StringIO.StringIO()
    writer = csv.writer(output)
    for i in range(0, len(distances)):
      writer.writerow([
        urllib.unquote(origin),
        urllib.unquote(destinations[i]),
        distances[i]]) 
    
    print output.getvalue()
    
    return 0


def make_parser():
    usage = """%prog: [csvFile]

Print the distance between an origin and multiple destinations.
Provide a CSV file with the following information:
The origin (e.g. "Los Angeles, CA") in the first cell
and the destinations in cells of the second column."""
    parser = OptionParser(usage)
    return parser

if __name__ == "__main__":
    sys.exit(main(sys.argv[1:]))