PostGIS with SQLAlchemy

Postgres is often said as the open-source world Oracle DB. It is shipped with different kind of index type. The default is B-tree, the others are R-Tree and GIST and GIN respectively. PostGIS is built for indexing geometry objects, and it is built on Postgres’s GIST type index. On AWS RDS you could also switch it on by following the instructions

To take the most of it and build fast prototypes, we still need ORM abstraction for PostGIS extension. The popular Sqlalchemy ORM in python world comes with geoalchemy extension. It provides functions from PostGIS.

To use it, you have to import it into your model file

from geoalchemy2 import Geometry

And define the column with Geometry class

geom = Column(Geometry(‘POINT’), nullable=False)

And insert to the model by assigning it a WKTElement with correct srid

s = ‘POINT(%s %s)’ %(geocode[“latitude”], geocode[“longitude”])
l.geom = WKTElement(s, srid=4326)

Then you could do the common operation using spatial functions

from geoalchemy2 import functions