Using PostGIS on Python 3

Question

I'm using Python 3 and need to connect to postGre with postGIS extensions. I'm intending to use a psycopg2 driver.
This PPyGIS is the only extension I found, but it works on python 2.7 not 3.3.0.
Any one knows a solution working on 3.3.0 ?

Answer 1

If you are not doing anything fancy with the geometry objects on the client side (Python), psycopg2 can get most basic info using native data types with geometry accessors, or other GIS output formats like GeoJSON. Let the server (PostgreSQL/PostGIS) do the hard work.

Here is a random example to return the GeoJSON to shapes that are within 1 km of a point of interest:

import psycopg2
conn = psycopg2.connect(database='postgis', user='postgres')
curs = conn.cursor()

# Find the distance within 1 km of point-of-interest
poi = (-124.3, 53.2)  # longitude, latitude

# Table 'my_points' has a geography column 'geog'
curs.execute("""\
SELECT gid, ST_AsGeoJSON(geog), ST_Distance(geog, poi)
FROM my_points, (SELECT ST_MakePoint(%s, %s)::geography AS poi) AS f
WHERE ST_DWithin(geog, poi, 1000);""", poi)

for row in curs.fetchall():
    print(row)

Answer 2

You may actually use Shapely or GDAL/OGR, but both libraries have a long list of dependencies.

If you have only very few usecases, you might also implement a small protocol yourself, based on the super slick pygeoif library, like the example below

from psycopg2.extensions import register_adapter, AsIs, adapt
from pygeoif.geometry import Point

def adapt_point(pt):
    return AsIs("ST_SetSRID(ST_MakePoint({}, {}), 4326)".format(adapt(pt.x), adapt(pt.y)))

register_adapter(Point, adapt_point)