Set string length in write_netcdf()

conda_package/mpas_tools/io.py

@@ -13,6 +13,7 @@
 default_engine = None
 default_char_dim_name = 'StrLen'
 default_fills = netCDF4.default_fillvals
+default_nchar = 64
 
 
 def write_netcdf(
@@ -23,6 +24,7 @@ def write_netcdf(
     engine=None,
     char_dim_name=None,
     logger=None,
+    nchar=None,
 ):
     """
     Write an xarray.Dataset to a file with NetCDF4 fill values and the given
@@ -31,9 +33,9 @@ def write_netcdf(
 
     Note: the ``NETCDF3_64BIT_DATA`` format is handled as a special case
     because xarray output with this format is not performant. First, the file
-    is written in `NETCDF4` format, which supports larger files and variables.
-    Then, the `ncks` command is used to convert the file to the
-    `NETCDF3_64BIT_DATA` format.
+    is written in ``NETCDF4`` format, which supports larger files and
+    variables. Then, the ``ncks`` command is used to convert the file to the
+    ``NETCDF3_64BIT_DATA`` format.
 
     Note: All int64 variables are automatically converted to int32 for MPAS
     compatibility.
@@ -63,15 +65,19 @@ def write_netcdf(
         ``mpas_tools.io.default_engine``
 
     char_dim_name : str, optional
-        The name of the dimension used for character strings, or None to let
-        xarray figure this out. Default is
+        The name of the dimension used for character strings. Default is
         ``mpas_tools.io.default_char_dim_name``, which can be modified but
         which defaults to ``'StrLen'``
 
+    nchar : int, optional
+        The number of characters to use for string variables.  If None, the
+        default is ``mpas_tools.io.default_nchar``, which can be modified but
+        which defaults to 64.
+
     logger : logging.Logger, optional
-        A logger to write messages to write the output of `ncks` conversion
-        calls to.  If None, `ncks` output is suppressed.  This is only
-        relevant if `format` is 'NETCDF3_64BIT_DATA'
+        A logger to write messages to write the output of ``ncks`` conversion
+        calls to.  If None, ``ncks`` output is suppressed.  This is only
+        relevant if ``format`` is 'NETCDF3_64BIT_DATA'
     """  # noqa: E501
     if format is None:
         format = default_format
@@ -85,31 +91,43 @@ def write_netcdf(
     if char_dim_name is None:
         char_dim_name = default_char_dim_name
 
-    # Convert int64 variables to int32 for MPAS compatibility
-    for var in list(ds.data_vars.keys()) + list(ds.coords.keys()):
-        if ds[var].dtype == numpy.int64:
-            attrs = ds[var].attrs.copy()
-            ds[var] = ds[var].astype(numpy.int32)
-            ds[var].attrs = attrs
+    if nchar is None:
+        nchar = default_nchar
+
+    numpyFillValues = {}
+    for fillType in fillValues:
+        # drop string fill values
+        if not fillType.startswith('S'):
+            numpyFillValues[numpy.dtype(fillType)] = fillValues[fillType]
 
     encodingDict = {}
     variableNames = list(ds.data_vars.keys()) + list(ds.coords.keys())
     for variableName in variableNames:
-        isNumeric = numpy.issubdtype(ds[variableName].dtype, numpy.number)
-        if isNumeric and numpy.any(numpy.isnan(ds[variableName])):
-            dtype = ds[variableName].dtype
-            for fillType in fillValues:
-                if dtype == numpy.dtype(fillType):
-                    encodingDict[variableName] = {
-                        '_FillValue': fillValues[fillType]
-                    }
-                    break
-        else:
-            encodingDict[variableName] = {'_FillValue': None}
-
-        isString = numpy.issubdtype(ds[variableName].dtype, numpy.bytes_)
-        if isString and char_dim_name is not None:
-            encodingDict[variableName] = {'char_dim_name': char_dim_name}
+        var = ds[variableName]
+        encodingDict[variableName] = {}
+        dtype = var.dtype
+
+        # Convert int64 variables to int32 for MPAS compatibility
+        if dtype == numpy.int64:
+            encodingDict[variableName]['dtype'] = 'int32'
+
+        # add fill values
+        if dtype in numpyFillValues:
+            if numpy.any(numpy.isnan(var)):
+                # only add fill values if they're needed
+                fill = numpyFillValues[dtype]
+            else:
+                fill = None
+            encodingDict[variableName]['_FillValue'] = fill
+
+        isString = numpy.issubdtype(dtype, numpy.bytes_) or numpy.issubdtype(
+            dtype, numpy.str_
+        )
+        if isString:
+            # set the encoding for string variables
+            encodingDict[variableName].update(
+                {'dtype': f'|S{nchar}', 'char_dim_name': char_dim_name}
+            )
 
     update_history(ds)
 

conda_package/mpas_tools/mesh/mask.py

@@ -13,7 +13,7 @@
 from shapely.strtree import STRtree
 
 from mpas_tools.cime.constants import constants
-from mpas_tools.io import write_netcdf
+from mpas_tools.io import default_nchar, write_netcdf
 from mpas_tools.logging import LoggingContext
 from mpas_tools.parallel import create_pool
 from mpas_tools.transects import (
@@ -100,7 +100,7 @@ def compute_mpas_region_masks(
 
         # create shapely geometry for lon and lat
         points = [shapely.geometry.Point(x, y) for x, y in zip(lon, lat)]
-        regionNames, masks, properties, nchar = _compute_region_masks(
+        regionNames, masks, properties = _compute_region_masks(
             fcMask,
             points,
             logger,
@@ -133,7 +133,6 @@ def compute_mpas_region_masks(
             ds=dsMasks,
             properties=properties,
             dim='nRegions',
-            nchar=nchar,
         )
 
     if logger is not None:
@@ -339,17 +338,15 @@ def compute_mpas_transect_masks(
         polygons, nPolygons, duplicatePolygons = _get_polygons(
             dsMesh, maskType
         )
-        transectNames, masks, properties, nchar, shapes = (
-            _compute_transect_masks(
-                fcMask,
-                polygons,
-                logger,
-                pool,
-                chunkSize,
-                showProgress,
-                subdivisionResolution,
-                earthRadius,
-            )
+        transectNames, masks, properties, shapes = _compute_transect_masks(
+            fcMask,
+            polygons,
+            logger,
+            pool,
+            chunkSize,
+            showProgress,
+            subdivisionResolution,
+            earthRadius,
         )
 
         if logger is not None:
@@ -393,7 +390,6 @@ def compute_mpas_transect_masks(
             ds=dsMasks,
             properties=properties,
             dim='nTransects',
-            nchar=nchar,
         )
 
     if logger is not None:
@@ -723,7 +719,7 @@ def compute_lon_lat_region_masks(
 
     # create shapely geometry for lon and lat
     points = [shapely.geometry.Point(x, y) for x, y in zip(Lon, Lat)]
-    regionNames, masks, properties, nchar = _compute_region_masks(
+    regionNames, masks, properties = _compute_region_masks(
         fcMask,
         points,
         logger,
@@ -757,7 +753,6 @@ def compute_lon_lat_region_masks(
         ds=dsMasks,
         properties=properties,
         dim='nRegions',
-        nchar=nchar,
     )
 
     if logger is not None:
@@ -959,7 +954,7 @@ def compute_projection_grid_region_masks(
     points = [
         shapely.geometry.Point(x, y) for x, y in zip(lon.ravel(), lat.ravel())
     ]
-    regionNames, masks, properties, nchar = _compute_region_masks(
+    regionNames, masks, properties = _compute_region_masks(
         fcMask,
         points,
         logger,
@@ -990,7 +985,6 @@ def compute_projection_grid_region_masks(
         ds=dsMasks,
         properties=properties,
         dim='nRegions',
-        nchar=nchar,
     )
 
     if logger is not None:
@@ -1171,10 +1165,11 @@ def _compute_mask_from_shapes(
     return mask
 
 
-def _add_properties(ds, properties, dim, nchar):
+def _add_properties(ds, properties, dim):
     """
     Add properties to the dataset from a dictionary of properties
     """
+    nchar = default_nchar
     for name, prop_list in properties.items():
         if name not in ds:
             if isinstance(prop_list[0], str):
@@ -1186,7 +1181,7 @@ def _add_properties(ds, properties, dim, nchar):
                 for index, value in enumerate(prop_list):
                     ds[name][index] = value
             else:
-                ds[name] = ((dim,), properties[prop_list])
+                ds[name] = ((dim,), prop_list)
 
 
 def _get_region_names_and_properties(fc):
@@ -1208,19 +1203,16 @@ def _get_region_names_and_properties(fc):
                 propertyNames.add(propertyName)
 
     properties = {}
-    nchar = 0
     for propertyName in propertyNames:
         properties[propertyName] = []
         for feature in fc.features:
             if propertyName in feature['properties']:
                 propertyVal = feature['properties'][propertyName]
                 properties[propertyName].append(propertyVal)
-                if isinstance(propertyVal, str):
-                    nchar = max(nchar, len(propertyVal))
             else:
                 properties[propertyName].append('')
 
-    return regionNames, properties, nchar
+    return regionNames, properties
 
 
 def _compute_region_masks(
@@ -1231,7 +1223,7 @@ def _compute_region_masks(
     a set of regions.
     """
 
-    regionNames, properties, nchar = _get_region_names_and_properties(fcMask)
+    regionNames, properties = _get_region_names_and_properties(fcMask)
 
     masks = []
 
@@ -1253,11 +1245,9 @@ def _compute_region_masks(
             showProgress=showProgress,
         )
 
-        nchar = max(nchar, len(name))
-
         masks.append(mask)
 
-    return regionNames, masks, properties, nchar
+    return regionNames, masks, properties
 
 
 def _contains(shapes, points):
@@ -1355,7 +1345,7 @@ def _compute_transect_masks(
     a set of transects.
     """
 
-    transectNames, properties, nchar = _get_region_names_and_properties(fcMask)
+    transectNames, properties = _get_region_names_and_properties(fcMask)
 
     masks = []
     shapes = []
@@ -1405,12 +1395,10 @@ def _compute_transect_masks(
             showProgress=showProgress,
         )
 
-        nchar = max(nchar, len(name))
-
         masks.append(mask)
         shapes.append(shape)
 
-    return transectNames, masks, properties, nchar, shapes
+    return transectNames, masks, properties, shapes
 
 
 def _intersects(shape, polygons):