Ensure objects containing Cubes are saved as netCDF files

improver/cli/__init__.py

@@ -353,7 +353,16 @@ def with_output(
 
     result = wrapped(*args, **kwargs)
 
-    if output and (isinstance(result, Cube) or isinstance(result, CubeList)):
+    # If result is a Cube or CubeList or an iterable containing only Cubes,
+    # save as netCDF
+    if (
+        output
+        and result
+        and (
+            (isinstance(result, (Cube, CubeList)))
+            or all([isinstance(x, Cube) for x in result])
+        )
+    ):
         save_netcdf(result, output, compression_level, least_significant_digit)
         if pass_through_output:
             return ObjectAsStr(result, output)

improver/psychrometric_calculations/cloud_condensation_level.py

@@ -45,7 +45,7 @@ def __init__(self, model_id_attr: str = None):
             model_id_attr=model_id_attr
         )
 
-    def process(self, *cubes: Union[Cube, CubeList]) -> Tuple[Cube, Cube]:
+    def process(self, *cubes: Union[Cube, CubeList]) -> CubeList[Cube, Cube]:
         """
         Call HumidityMixingRatio followed by CloudCondensationLevel to calculate cloud
         condensation level.
@@ -138,7 +138,7 @@ def humidity_delta(p2, p, t, q):
         ).astype(np.float32)
         return ccl_pressure, ccl_temperature
 
-    def process(self, *cubes: Union[Cube, CubeList]) -> Tuple[Cube, Cube]:
+    def process(self, *cubes: Union[Cube, CubeList]) -> CubeList[Cube, Cube]:
         """
         Calculates the cloud condensation level from the near-surface inputs.
         Values will be limited to the surface values where the calculated pressure is greater than
@@ -164,7 +164,9 @@ def process(self, *cubes: Union[Cube, CubeList]) -> Tuple[Cube, Cube]:
         mask = ccl_pressure > self.pressure.data
         ccl_pressure = np.where(mask, self.pressure.data, ccl_pressure)
         ccl_temperature = np.where(mask, self.temperature.data, ccl_temperature)
-        return (
-            self._make_ccl_cube(ccl_temperature, is_temperature=True),
-            self._make_ccl_cube(ccl_pressure, is_temperature=False),
+        return CubeList(
+            [
+                self._make_ccl_cube(ccl_temperature, is_temperature=True),
+                self._make_ccl_cube(ccl_pressure, is_temperature=False),
+            ]
         )

improver/utilities/spatial.py

@@ -681,7 +681,7 @@ def _create_output_cube(gradient: Cube, name: str) -> Cube:
         )
         return grad_cube
 
-    def process(self, cube: Cube) -> Tuple[Cube, Cube]:
+    def process(self, cube: Cube) -> CubeList[Cube, Cube]:
         """
         Calculate the gradient along the x and y axes and return
         the result in separate cubes. The difference along each axis is
@@ -699,7 +699,7 @@ def process(self, cube: Cube) -> Tuple[Cube, Cube]:
               y-axis.
         """
         axis = ["x", "y"]
-        gradients = []
+        gradients = CubeList([])
         diffs = DifferenceBetweenAdjacentGridSquares()(cube)
         distances = DistanceBetweenGridSquares()(cube)
 
@@ -713,7 +713,7 @@ def process(self, cube: Cube) -> Tuple[Cube, Cube]:
                 grad_cube = grad_cube.regrid(cube, iris.analysis.Linear())
             gradients.append(grad_cube)
 
-        return tuple(gradients)
+        return gradients
 
 
 def maximum_within_vicinity(

improver_tests/psychrometric_calculations/cloud_condensation_level/test_CloudCondensationLevel.py

@@ -9,7 +9,7 @@
 import numpy as np
 import pytest
 from iris.coords import AuxCoord
-from iris.cube import Cube
+from iris.cube import Cube, CubeList
 
 from improver.metadata.constants.attributes import MANDATORY_ATTRIBUTES
 from improver.psychrometric_calculations.cloud_condensation_level import (
@@ -125,6 +125,7 @@ def test_basic(
     humidity.data = np.full_like(humidity.data, humidity_value)
     result = CloudCondensationLevel()([temperature, pressure, humidity])
     metadata_ok(result, temperature)
+    assert isinstance(result, CubeList)
     assert np.isclose(result[0].data, expected_t, atol=1e-2).all()
     assert np.isclose(result[1].data, expected_p, atol=1e-0).all()
 

improver_tests/utilities/spatial/test_GradientBetweenAdjacentGridSquares.py

@@ -6,6 +6,7 @@
 
 import numpy as np
 import pytest
+from iris.cube import CubeList
 
 from improver.metadata.constants.attributes import MANDATORY_ATTRIBUTE_DEFAULTS
 from improver.synthetic_data.set_up_test_cubes import set_up_variable_cube
@@ -135,7 +136,9 @@ def test_metadata(
     expected_x_coord = cube.coord(axis="x").copy(expected_x_points)
     expected_y_coord = cube.coord(axis="y").copy(expected_y_points)
     plugin = GradientBetweenAdjacentGridSquares(regrid=regrid)
-    result_x, result_y = plugin(cube)
+    result = plugin(cube)
+    assert isinstance(result, CubeList)
+    result_x, result_y = result
     for result, name in [(result_x, "x"), (result_y, "y")]:
         assert result.name() == f"gradient_of_air_temperature_wrt_{name}"
         assert result.units == "K m-1"