plpygis 0.0.2

PostGIS Python tools

plpygis is a Python conveter to and from the PostGIS geometry type, WKB, EWKB, GeoJSON and Shapely geometries and additionally supports __geo_interface__. plpygis is intended for use in PL/Python functions.

Basic usage

The Geometry class and its subclasses can be used to convert to and from PostGIS geometries. The following example will take a PostGIS multipolygon geometry named geom and find its largest component polygon.

Geometry() can convert a Postigs geometry that has been passed as a parameter to a PL/Python function. A Geometry that is returned from the PL/Python function will automatically be converted back to a PostGIS geometry.

CREATE OR REPLACE FUNCTION largest_poly(geom geometry)
  RETURNS geometry
AS $$
  from plpygis import Geometry
  polygons = Geometry(geom)
  if polygons.type == "Polygon":
      return polygons
  elif polygons.type == "MultiPolygon":
      largest = max(polygons.shapely, key=lambda polygon: polygon.area)
      return Geometry.from_shapely(largest)
  else:
      return None
$$ LANGUAGE plpythonu;