Geocoding with Python

The following code snippet is intended to demonstrate how you can leverage Python and the Google Maps/Geocode API to query the coordinates of two zip codes and then determine the distance between them. Both functions have far reaching uses independently which will be further demonstrated in future posts.

This example determines distance between the two points in miles, however it can be modified to return distance in kilometers by replacing 3959.0 (the average radius of the earth in miles) with 6371.0 (the radius in kilometers).

This code does no validation on the existence of the zip code, and will likely return valid coordinates of something (whatever Google thinks you really meant) when you pass it a non existent zip code.

The original geocode code was found here.

Note: You will have to provide your Google Maps API key in the key variable.

import math
import urllib

def get_lat_long(location):
        key = ""
        output = "csv"
        location = urllib.quote_plus(location)
        request = "http://maps.google.com/maps/geo?q=%s&output=%s&key=%s" % (location, output, key)
        data = urllib.urlopen(request).read()
        dlist = data.split(',')
        if dlist[0] == '200':
                return dlist[2], dlist[3]
        else:
                return None, None

def calculate_distance(zip1, zip2):
        lat1, lon1 = get_lat_long(zip1)
        lat2, lon2 = get_lat_long(zip2)

        if (not lat1) or (not lon1) or (not lat2) or (not lon2):
                return -1

        lat1 = float(lat1) * math.pi/180
        lon1 = float(lon1) * math.pi/180
        lat2 = float(lat2) * math.pi/180
        lon2 = float(lon2) * math.pi/180

        return 3959.0 * math.acos(math.sin(lat1) * math.sin(lat2) + math.cos(lat1) * math.cos(lat2) * math.cos(lon2-lon1))