Return SETOF Points from plpython/Postgis

Question

I would like to create a function in pl/python3 / postgis that returns a set of geometry records (for example points). I managed to create a dictionary with the coordinates of my points, but I can't figure out how to turn them into actual postgis "point" geoms. This is my code so far:

CREATE OR REPLACE FUNCTION grid_points()
  RETURNS text AS
  $$

  grid_cell_length_x = 2
  grid_cell_length_y = 1

  grid_points = {}

  for i in range(0, 3):
    for j in range(0,3):
      key   = "grid_poin_" + str(i) + "" + str(j)

      x = 5  + i * grid_cell_length_x
      y = 10 - j * grid_cell_length_y

      value = (x, y)
      grid_points[key] = value

  return(
  grid_points)

$$
LANGUAGE plpython3u;

select grid_points();

Answer 1

You can use plyp.execute to access geometry objects and return them from functions -- although the return type will essentially be a hex encoded string representing the geometry.

CREATE OR REPLACE FUNCTION grid_points () 
  RETURNS SETOF geometry AS $$

  pts = plpy.execute ("SELECT geom FROM sometable WHERE ...")

  return pts
 $$
LANGUAGE plpython3u;

There are also a couple of examples on this link.

In your case you might want to use ST_MakePoint or ST_GeomFromText to actually construct the points within the procedure.

Alternatively, you could use a library like shapely inside a plpython proc.