Removing fieldtype argument from Field constructor

As it's more pythonic to attach UnitConverters directly to a field?

See also #1883 (comment)

Author: erikvansebille

docs/examples/tutorial_kernelloop.ipynb

@@ -118,7 +118,9 @@
     "    \"V\": \"northward_eulerian_current_velocity\",\n",
     "}\n",
     "dimensions = {\"lat\": \"lat\", \"lon\": \"lon\", \"time\": \"time\"}\n",
-    "fieldset = parcels.FieldSet.from_netcdf(filenames, variables, dimensions)\n",
+    "fieldset = parcels.FieldSet.from_netcdf(\n",
+    "    filenames, variables, dimensions, allow_time_extrapolation=True\n",
+    ")\n",
     "# uppermost layer in the hydrodynamic data\n",
     "fieldset.mindepth = fieldset.U.depth[0]"
    ]
@@ -137,11 +139,15 @@
     "    lon=fieldset.U.lon,\n",
     "    lat=fieldset.U.lat,\n",
     "    mesh=\"spherical\",\n",
-    "    fieldtype=\"U\",\n",
     ")\n",
     "VWind = parcels.Field(\n",
-    "    \"VWind\", np.zeros((ydim, xdim), dtype=np.float32), grid=UWind.grid, fieldtype=\"V\"\n",
+    "    \"VWind\",\n",
+    "    np.zeros((ydim, xdim), dtype=np.float32),\n",
+    "    grid=UWind.grid,\n",
     ")\n",
+    "UWind.units = parcels.tools.converters.GeographicPolar()\n",
+    "VWind.units = parcels.tools.converters.Geographic()\n",
+    "\n",
     "fieldset_wind = parcels.FieldSet(UWind, VWind)\n",
     "\n",
     "fieldset.add_field(fieldset_wind.U, name=\"UWind\")\n",

docs/examples/tutorial_unitconverters.ipynb

@@ -326,31 +326,6 @@
     "print(fieldset.Ustokes[0, 0, 40, -5])\n",
     "print(fieldset.Ustokes[0, 0, 40, -5] * 1852 * 60 * np.cos(40 * np.pi / 180))"
    ]
-  },
-  {
-   "attachments": {},
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "Alternatively, the UnitConverter can be set when the `FieldSet` or `Field` is created by using the `fieldtype` argument (use a dictionary in the case of `FieldSet` construction.\n"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "fieldset.add_field(\n",
-    "    parcels.Field(\n",
-    "        \"Ustokes2\",\n",
-    "        np.ones((ydim, xdim), dtype=np.float32),\n",
-    "        grid=fieldset.U.grid,\n",
-    "        fieldtype=\"U\",\n",
-    "    )\n",
-    ")\n",
-    "print(fieldset.Ustokes2[0, 0, 40, -5])"
-   ]
   }
  ],
  "metadata": {

parcels/field.py

@@ -123,8 +123,6 @@ class Field:
     grid : parcels.grid.Grid
         :class:`parcels.grid.Grid` object containing all the lon, lat depth, time
         mesh and time_origin information. Can be constructed from any of the Grid objects
-    fieldtype : str
-        Type of Field to be used for UnitConverter (either 'U', 'V', 'Kh_zonal', 'Kh_meridional' or None)
     time_origin : parcels.tools.converters.TimeConverter
         Time origin of the time axis (only if grid is None)
     interp_method : str
@@ -148,7 +146,6 @@ def __init__(
         time=None,
         grid=None,
         mesh: Mesh = "flat",
-        fieldtype=None,
         time_origin: TimeConverter | None = None,
         interp_method: InterpMethod = "linear",
         allow_time_extrapolation: bool | None = None,
@@ -170,13 +167,10 @@ def __init__(
                 time_origin = TimeConverter(0)
             self._grid = Grid.create_grid(lon, lat, depth, time, time_origin=time_origin, mesh=mesh)
         self.igrid = -1
-        self.fieldtype = self.name if fieldtype is None else fieldtype
-        if self.grid.mesh == "flat" or (self.fieldtype not in unitconverters_map.keys()):
-            self.units = UnitConverter()
-        elif self.grid.mesh == "spherical":
-            self.units = unitconverters_map[self.fieldtype]
+        if self.grid.mesh == "spherical" and self.name in unitconverters_map.keys():
+            self.units = unitconverters_map[self.name]
         else:
-            raise ValueError("Unsupported mesh type. Choose either: 'spherical' or 'flat'")
+            self.units = UnitConverter()
         if isinstance(interp_method, dict):
             if self.name in interp_method:
                 self.interp_method = interp_method[self.name]

parcels/fieldset.py

@@ -279,7 +279,6 @@ def from_netcdf(
         filenames,
         variables,
         dimensions,
-        fieldtype=None,
         mesh: Mesh = "spherical",
         allow_time_extrapolation: bool | None = None,
         **kwargs,
@@ -305,9 +304,6 @@ def from_netcdf(
             Note that dimensions can also be a dictionary of dictionaries if
             dimension names are different for each variable
             (e.g. dimensions['U'], dimensions['V'], etc).
-        fieldtype :
-            Optional dictionary mapping fields to fieldtypes to be used for UnitConverter.
-            (either 'U', 'V', 'Kh_zonal', 'Kh_meridional' or None) (Default value = None)
         mesh : str
             String indicating the type of mesh coordinates and
             units used during velocity interpolation, see also `this tutorial <../examples/tutorial_unitconverters.ipynb>`__:
@@ -353,7 +349,6 @@ def from_netcdf(
             # Use dimensions[var] if it's a dict of dicts
             dims = dimensions[var] if var in dimensions else dimensions
             cls.checkvaliddimensionsdict(dims)
-            fieldtype = fieldtype[var] if (fieldtype and var in fieldtype) else fieldtype
 
             grid = None
 
@@ -364,7 +359,6 @@ def from_netcdf(
                 grid=grid,
                 mesh=mesh,
                 allow_time_extrapolation=allow_time_extrapolation,
-                fieldtype=fieldtype,
                 **kwargs,
             )
 
@@ -426,9 +420,6 @@ def from_nemo(
             (for indexing details: https://www.nemo-ocean.eu/doc/img360.png )
             In 3D, the depth is the one corresponding to W nodes
             The gridindexingtype is set to 'nemo'. See also the Grid indexing documentation on oceanparcels.org
-        fieldtype :
-            Optional dictionary mapping fields to fieldtypes to be used for UnitConverter.
-            (either 'U', 'V', 'Kh_zonal', 'Kh_meridional' or None)
         mesh : str
             String indicating the type of mesh coordinates and
             units used during velocity interpolation, see also `this tutorial <../examples/tutorial_unitconverters.ipynb>`__:
@@ -635,9 +626,6 @@ def from_c_grid_dataset(
             which are located on the corners of the cells.
             (for indexing details: https://www.nemo-ocean.eu/doc/img360.png )
             In 3D, the depth is the one corresponding to W nodes.
-        fieldtype :
-            Optional dictionary mapping fields to fieldtypes to be used for UnitConverter.
-            (either 'U', 'V', 'Kh_zonal', 'Kh_meridional' or None)
         mesh : str
             String indicating the type of mesh coordinates and
             units used during velocity interpolation, see also `this tutorial <../examples/tutorial_unitconverters.ipynb>`__:
@@ -738,9 +726,6 @@ def from_mom5(
             Note that W is normally directed upward in MOM5, but Parcels requires W
             in the positive z-direction (downward) so W is multiplied by -1.
             T node is at the cell centre, and constant per cell.
-        fieldtype :
-            Optional dictionary mapping fields to fieldtypes to be used for UnitConverter.
-            (either 'U', 'V', 'Kh_zonal', 'Kh_meridional' or None)
         mesh : str
             String indicating the type of mesh coordinates and
             units used during velocity interpolation, see also the `Unit converters tutorial <../examples/tutorial_unitconverters.ipynb>`__:
@@ -841,9 +826,6 @@ def from_b_grid_dataset(
             W nodes are at the centre of the horizontal interfaces.
             They are interpolated linearly (as a function of z) in the cell.
             T node is at the cell centre, and constant per cell.
-        fieldtype :
-            Optional dictionary mapping fields to fieldtypes to be used for UnitConverter.
-            (either 'U', 'V', 'Kh_zonal', 'Kh_meridional' or None)
         mesh : str
             String indicating the type of mesh coordinates and
             units used during velocity interpolation, see also `this tutorial <../examples/tutorial_unitconverters.ipynb>`__:
@@ -908,9 +890,6 @@ def from_xarray_dataset(cls, ds, variables, dimensions, mesh="spherical", allow_
             Note that dimensions can also be a dictionary of dictionaries if
             dimension names are different for each variable
             (e.g. dimensions['U'], dimensions['V'], etc).
-        fieldtype :
-            Optional dictionary mapping fields to fieldtypes to be used for UnitConverter.
-            (either 'U', 'V', 'Kh_zonal', 'Kh_meridional' or None)
         mesh : str
             String indicating the type of mesh coordinates and
             units used during velocity interpolation, see also `this tutorial <../examples/tutorial_unitconverters.ipynb>`__:

tests/test_fieldset.py

@@ -13,10 +13,6 @@
     Variable,
 )
 from parcels.field import Field, VectorField
-from parcels.tools.converters import (
-    GeographicPolar,
-    UnitConverter,
-)
 from tests.utils import TEST_DATA
 
 
@@ -161,31 +157,6 @@ def test_fieldset_from_modulefile():
         FieldSet.from_modulefile(nemo_error_fname, modulename="none_returning_function")
 
 
-def test_field_from_netcdf_fieldtypes():
-    filenames = {
-        "varU": {
-            "lon": str(TEST_DATA / "mask_nemo_cross_180lon.nc"),
-            "lat": str(TEST_DATA / "mask_nemo_cross_180lon.nc"),
-            "data": str(TEST_DATA / "Uu_eastward_nemo_cross_180lon.nc"),
-        },
-        "varV": {
-            "lon": str(TEST_DATA / "mask_nemo_cross_180lon.nc"),
-            "lat": str(TEST_DATA / "mask_nemo_cross_180lon.nc"),
-            "data": str(TEST_DATA / "Vv_eastward_nemo_cross_180lon.nc"),
-        },
-    }
-    variables = {"varU": "U", "varV": "V"}
-    dimensions = {"lon": "glamf", "lat": "gphif"}
-
-    # first try without setting fieldtype
-    fset = FieldSet.from_nemo(filenames, variables, dimensions)
-    assert isinstance(fset.varU.units, UnitConverter)
-
-    # now try with setting fieldtype
-    fset = FieldSet.from_nemo(filenames, variables, dimensions, fieldtype={"varU": "U", "varV": "V"})
-    assert isinstance(fset.varU.units, GeographicPolar)
-
-
 def test_fieldset_from_agrid_dataset():
     filenames = {
         "lon": str(TEST_DATA / "mask_nemo_cross_180lon.nc"),
@@ -250,18 +221,18 @@ def test_add_duplicate_field(dupobject):
             fieldset.add_field(field2)
 
 
-@pytest.mark.parametrize("fieldtype", ["normal", "vector"])
-def test_add_field_after_pset(fieldtype):
+@pytest.mark.parametrize("field_type", ["normal", "vector"])
+def test_add_field_after_pset(field_type):
     data, dimensions = generate_fieldset_data(100, 100)
     fieldset = FieldSet.from_data(data, dimensions)
     pset = ParticleSet(fieldset, Particle, lon=0, lat=0)  # noqa ; to trigger fieldset._check_complete
     field1 = Field("field1", fieldset.U.data, lon=fieldset.U.lon, lat=fieldset.U.lat)
     field2 = Field("field2", fieldset.U.data, lon=fieldset.U.lon, lat=fieldset.U.lat)
     vfield = VectorField("vfield", field1, field2)
     with pytest.raises(RuntimeError):
-        if fieldtype == "normal":
+        if field_type == "normal":
             fieldset.add_field(field1)
-        elif fieldtype == "vector":
+        elif field_type == "vector":
             fieldset.add_vector_field(vfield)