GPolyline decoding in Python

I am currently working on providing GPX data for routes on http://zoomaroundtown.appspot.com. As the routes are stored as Google Map GPolyline encoded strings in the datastore, I need a way to decode them back into latitude and longitude points before I can create the respective GPX files. Mark McClure has an excellent page on this topic. Apart from his Javascript implementation, I have also found a PHP port of the decoder function. However, there does not seem to the any Python port, so I created a straightforward port:

You can donwload the Python file here.

def decode_line(encoded):

    """Decodes a polyline that was encoded using the Google Maps method.

    See http://code.google.com/apis/maps/documentation/polylinealgorithm.html
    
    This is a straightforward Python port of Mark McClure's JavaScript polyline decoder
    (http://facstaff.unca.edu/mcmcclur/GoogleMaps/EncodePolyline/decode.js)
    and Peter Chng's PHP polyline decode
    (http://unitstep.net/blog/2008/08/02/decoding-google-maps-encoded-polylines-using-php/)
    """

    encoded_len = len(encoded)
    index = 0
    array = []
    lat = 0
    lng = 0

    while index < encoded_len:

        b = 0
        shift = 0
        result = 0

        while True:
            b = ord(encoded[index]) - 63
            index = index + 1
            result |= (b & 0x1f) << shift
            shift += 5
            if b < 0x20:
                break

        dlat = ~(result >> 1) if result & 1 else result >> 1
        lat += dlat

        shift = 0
        result = 0

        while True:
            b = ord(encoded[index]) - 63
            index = index + 1
            result |= (b & 0x1f) << shift
            shift += 5
            if b < 0x20:
                break

        dlng = ~(result >> 1) if result & 1 else result >> 1
        lng += dlng

        array.append((lat * 1e-5, lng * 1e-5))

    return array

if __name__ == "__main__":
    latlngs = decode_line("grkyHhpc@B[[_IYiLiEgj@a@q@yEoAGi@bEyH_@aHj@m@^qAB{@IkHi@cHcAkPSiMJqEj@s@CkFp@sDfB}Ex@iBj@S_AyIkCcUWgAaA_JUyAFk@{D_]~KiLwAeCsHqJmBlAmFuXe@{DcByIZIYiBxBwAc@eCcAl@y@aEdCcBVJpHsEyAeE")
    for latlng in latlngs:
        print str(latlng[0]) + "," + str(latlng[1])

Hope you Python GMap coders out there will find this useful!