Using Google Maps with Python to turn a list of addresses into waypoints
A few days ago I tlaked about how I use making waypoint files for a list of house addresses is OsmAnd. For waypoint files, you need latitude/longitude coordinates, and I was getting those from a web page that used the online Google Maps API to convert an address into latitude and longitude coordinates.
It was pretty cool at first, but pasting every address into the latitude/longitude web page and then pasting the resulting coordinates into the address file, got old, fast. That's exactly the sort of repetitive task that computers are supposed to handle for us.
The lat/lon page used Javascript and the Google Maps API. and I already had a Google Maps API key (they have all sorts of fun APIs for map geeks) ... but I really wanted something that could run locally, reading and converting a local file.
And then I discovered the
Python googlemaps
package. Exactly what I needed! It's in the Python Package Index,
so I installed it with
pip install googlemaps.
That enabled me to change my
waymaker
Python script: if the first line of a
description wasn't a latitude and longitude, instead it looked for
something that might be an address.
Addresses in my data files might be one line or might be two, but since they're all US addresses, I know they'll end with a two-capital-letter state abbreviation and a 5-digit zip code: 2948 W Main St. Anytown, NM 12345. You can find that with a regular expression:
match = re.search('.*[A-Z]{2}\s+\d{5}$', line)
But first I needed to check whether the first line of the entry was already latitude/longitude coordinates, since I'd already converted some of my files. That uses another regular expression. Python doesn't seem to have a built-in way to search for generic numeric expressions (containing digits, decimal points or +/- symbols) so I made one, since I had to use it twice if I was searching for two numbers with whitespace between them.
numeric = '[\+\-\d\.]' match = re.search('^(%s+)\s+(%s+)$' % (numeric, numeric), line)(For anyone who wants to quibble, I know the regular expression isn't perfect. For instance, it would match expressions like 23+48..6.1-64.5. Not likely to be a problem in these files, so I didn't tune it further.)
If the script doesn't find coordinates but does find something that looks like an address, it feeds the address into Google Maps and gets the resulting coordinates. That code looks like this:
from googlemaps import GoogleMaps gmaps = GoogleMaps('YOUR GOOGLE MAPS API KEY HERE') try: lat, lon = gmaps.address_to_latlng(addr) except googlemaps.GoogleMapsError, e: print "Oh, no! Couldn't geocode", addr print e
Overall, a nice simple solution made possible with python-googlemaps. The full script is on github: waymaker.
[ 12:24 Aug 20, 2013 More mapping | permalink to this entry | comments ]