plpygis can't find shapely dependency

Question

I have a problem with the plpygis library for python. Whenever I'm trying to convert a plpygis Point type into its shapely counterpart, I get the following error:

ERROR: plpygis.exceptions.DependencyError: Dependency 'Shapely' is not available.

The code is executed within a PL/Python function in Postgres. The code looks like this:

CREATE or REPLACE FUNCTION test(n int)
 RETURNS text
AS $$
from plpygis import Geometry, Point
coordinates = []
for i in range(n):
 srows = plpy.execute("...")
 for i in srows:
 point = Geometry(i['geom'])
 if point.type != "Point":
 pass
 coordinates.append(point.shapely)
return coordinates
$$ LANGUAGE plpython3u;

It fails on the line coordinates.append(point.shapely). The shapely library is installed in the same pip env as all other packages, and everything is up-to-date. Importing shapely by itself works perfectly fine.

I took a look into the plpygis source code and it determines the error by checking if this import is working:

 from shapely.geos import lgeos, WKBWriter

I checked it manually and the import didn't work, which is then the reason for the DependencyError.

Does anyone have an idea on why this is happening?

Answer 1

plpygis author here. Can you try a more recent version of plpygis? I suspect the issue is due to missing support for Shapely 2.x, but that has now been added.

• yarvis: Hi, I can't validate your answer, since I don't have access to the database anymore this was running on. It seems like it would've fixed the issue, though. Thank you very much for providing an answer after all this time.