Update GridID generation in tutorial_nestedgrids

Author: erikvansebille

docs/user_guide/examples/tutorial_nestedgrids.ipynb

@@ -309,10 +309,10 @@
     "        \"node_lon\": ((\"n_node\",), points[:, 0]),\n",
     "        \"node_lat\": ((\"n_node\",), points[:, 1]),\n",
     "        \"face_node_connectivity\": ((\"n_face\", \"n_max_face_nodes\"), face_tris),\n",
-    "        \"face_polygon\": (\n",
+    "        \"GridID\": (\n",
     "            (\n",
     "                \"time\",\n",
-    "                \"zf\",\n",
+    "                \"zc\",\n",
     "                \"n_face\",\n",
     "            ),\n",
     "            face_poly[np.newaxis, np.newaxis, :],\n",
@@ -325,23 +325,16 @@
     "    },\n",
     "    coords={\n",
     "        \"time\": np.array([np.timedelta64(0, \"ns\")]),\n",
-    "        \"zf\": np.array([0]),\n",
+    "        \"zf\": np.array([0, 1]),\n",
+    "        \"zc\": np.array([0.5]),\n",
     "        \"n_node\": np.arange(n_node),\n",
     "        \"n_face\": np.arange(n_face),\n",
     "    },\n",
     "    attrs={\"Conventions\": \"UGRID-1.0\"},\n",
     ")\n",
-    "\n",
-    "uxda = ux.UxDataArray(ds_tri[\"face_polygon\"], uxgrid=ux.Grid(ds_tri))\n",
-    "\n",
-    "GridID = parcels.Field(\n",
-    "    \"GridID\",\n",
-    "    uxda,\n",
-    "    # TODO note that here we need to use mesh=\"flat\" otherwise the hashing doesn't work. See https://github.com/Parcels-code/Parcels/pull/2439#discussion_r2627664010\n",
-    "    parcels.UxGrid(uxda.uxgrid, z=uxda[\"zf\"], mesh=\"flat\"),\n",
-    "    interp_method=parcels.interpolators.UxConstantFaceConstantZC,\n",
-    ")\n",
-    "fieldset = parcels.FieldSet([GridID])"
+    "uxda = ux.UxDataArray(ds_tri[\"GridID\"], uxgrid=ux.Grid(ds_tri)).to_dataset()\n",
+    "uxda = uxda.assign_coords({\"zf\": ds_tri.coords[\"zf\"]})\n",
+    "fieldset = parcels.FieldSet.from_ugrid_conventions(uxda, mesh=\"flat\")"
    ]
   },
   {
@@ -407,7 +400,7 @@
     "    fieldset.GridID.grid.uxgrid.node_lat.values,\n",
     "    triangles=fieldset.GridID.grid.uxgrid.face_node_connectivity.values,\n",
     ")\n",
-    "facecolors = np.squeeze(uxda[0, :].values)\n",
+    "facecolors = np.squeeze(uxda.GridID[0, :].values)\n",
     "\n",
     "ax.tripcolor(triang, facecolors=facecolors, shading=\"flat\", **plot_args)\n",
     "ax.scatter(pset.lon, pset.lat, c=pset.gridID, **plot_args)\n",
@@ -438,14 +431,15 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "fields = [GridID]\n",
     "for i, ds in enumerate(ds_in):\n",
     "    fset = parcels.FieldSet.from_sgrid_conventions(ds, mesh=\"spherical\")\n",
     "\n",
-    "    for fld in fset.fields.values():\n",
-    "        fld.name = f\"{fld.name}{i}\"\n",
-    "        fields.append(fld)\n",
-    "fieldset = parcels.FieldSet(fields)"
+    "    # Rename and add fields to the main fieldset\n",
+    "    # TODO This needs a beeter API!\n",
+    "    for old_name, fld in list(fset.fields.items()):\n",
+    "        new_name = f\"{old_name}{i}\"\n",
+    "        fld.name = new_name\n",
+    "        fieldset._fields[new_name] = fld"
    ]
   },
   {
@@ -471,7 +465,7 @@
     "    unique_ids = np.unique(particles.gridID)\n",
     "    for gid in unique_ids:\n",
     "        mask = particles.gridID == gid\n",
-    "        UVField = getattr(fieldset, f\"UV{gid}\")\n",
+    "        UVField = fieldset._fields[f\"UV{gid}\"]\n",
     "        (u[mask], v[mask]) = UVField[particles[mask]]\n",
     "\n",
     "    particles.dlon += u * particles.dt\n",
@@ -550,7 +544,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "docs",
+   "display_name": "Python 3",
    "language": "python",
    "name": "python3"
   },
@@ -564,7 +558,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.14.4"
+   "version": "3.14.6"
   }
  },
  "nbformat": 4,