fix for #223

hydropandas/obs_collection.py

@@ -812,6 +812,31 @@ def read_pastastore(
  )
 
 
+def _obscollection_constructor_with_fallback(*args, **kwargs):
+ """
+ A flexible constructor for ObsCollection._constructor, which falls back
+ to returning a DataFrame (if a certain operation does not preserve the
+ obs column). Copied from geopandas.
+ """
+ oc = ObsCollection(*args, **kwargs)
+ if 'obs' not in oc.columns:
+ oc = pd.DataFrame(oc)
+
+ return oc
+
+
+def is_observation_type(data):
+ """
+ Check if the data is of geometry dtype.
+
+ Does not include object array of shapely scalars.
+ """
+ if isinstance(getattr(data, "dtype", None), GeometryDtype):
+ # GeometryArray, GeoSeries and Series[GeometryArray]
+ return True
+ else:
+ return False
+
 class ObsCollection(pd.DataFrame):
  """Class for a collection of point observations.
 
@@ -871,7 +896,7 @@ def __init__(self, *args, **kwargs):
 
  @property
  def _constructor(self):
- return ObsCollection
+ return _obscollection_constructor_with_fallback
 
  def _infer_otype(self):
  """Infer observation type from the obs column.

tests/test_002_obs_objects.py

@@ -100,6 +100,17 @@ def test_copy_obs():
  assert "answer" in o3.meta.keys(), "copy method failed"
 
 
+def test_returns():
+ # check if a DataFrame is returned when an ObsCollection is sliced without the
+ # 'obs' column
+ oc = _obscollection_from_list()
+
+ assert isinstance(oc.loc[:, ["x", "y"]], pd.DataFrame)
+ assert not isinstance(oc.loc[:, ["x", "y"]], hpd.ObsCollection)
+
+ assert isinstance(oc.loc[:, ["x", "y", "obs"]], hpd.ObsCollection)
+
+
 def test_convert_waterlvl_groundwater_obs():
  # create WaterlvlObs
  df = pd.DataFrame(