petern48 commented on code in PR #2071:
URL: https://github.com/apache/sedona/pull/2071#discussion_r2199003816
##########
python/sedona/geopandas/geoseries.py:
##########
@@ -829,9 +829,78 @@ def get_precision(self):
# Implementation of the abstract method
raise NotImplementedError("This method is not implemented yet.")
- def get_geometry(self, index):
- # Implementation of the abstract method
- raise NotImplementedError("This method is not implemented yet.")
+ def get_geometry(self, index) -> "GeoSeries":
+ """Returns the n-th geometry from a collection of geometries.
+
+ Parameters
+ ----------
+ index : int or array_like
+ Position of a geometry to be retrieved within its collection
+
+ Returns
+ -------
+ GeoSeries
+
+ Notes
+ -----
+ Simple geometries act as collections of length 1. Any out-of-range
index value
+ returns None.
+
+ Examples
+ --------
+ >>> from shapely.geometry import Point, MultiPoint, GeometryCollection
+ >>> s = geopandas.GeoSeries(
+ ... [
Review Comment:
Polygon Empty isn't special, but MultiPolygon Empty is interesting, since
it's a collection. Our `ST_GeometryN` errors when we use a negative index out
of scope of the length of the Multi geometry object.
e.g
```sql
SELECT ST_GeometryN(MultiPolygon(Point(1, 1)), -2); -- errors
SELECT ST_GeometryN(MultiPolygon(), -1); -- errors
```
Geopandas returns null in this case. PostGIS also returns null in this case
(the PostGIS implementation is already very different than ours since they use
1-indexing).
We can either fix this on the java Sedona level, Python dataframe level or
just the geopandas level (case statement). Which do you think @jiayuasu ?
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