Add bits_per_value option when saving numpyfs grib data (#284)

earthkit/data/writers/grib.py

@@ -13,7 +13,7 @@
 class GribWriter(Writer):
     DATA_FORMAT = "grib"
 
-    def write(self, f, values, metadata, check_nans=True):
+    def write(self, f, values, metadata, check_nans=True, bits_per_value=16):
         r"""Write a GRIB field to a file object.
 
         Parameters
@@ -28,6 +28,9 @@ def write(self, f, values, metadata, check_nans=True):
             Replace nans in ``values`` with GRIB missing values when writing to``f``.
         """
         handle = metadata._handle.clone()
+
+        handle.set_long("bitsPerValue", bits_per_value)
+
         if check_nans:
             import numpy as np
 

tests/numpy_fs/test_numpy_fs_write.py

@@ -11,6 +11,7 @@
 
 import logging
 import os
+import sys
 
 import numpy as np
 import pytest
@@ -20,6 +21,10 @@
 from earthkit.data.core.temporary import temp_file
 from earthkit.data.testing import earthkit_examples_file
 
+here = os.path.dirname(__file__)
+sys.path.insert(0, here)
+from numpy_fs_fixtures import load_numpy_fs  # noqa: E402
+
 LOG = logging.getLogger(__name__)
 
 
@@ -144,6 +149,18 @@ def test_numpy_fs_grib_write_generating_proc_id():
         assert np.allclose(r_tmp.values[1], v2)
 
 
+@pytest.mark.parametrize(
+    "_kwargs,expected_value", [({}, 16), ({"bits_per_value": 12}, 12)]
+)
+def test_numpy_fs_grib_write_bits_per_value(_kwargs, expected_value):
+    ds, _ = load_numpy_fs(1)
+
+    with temp_file() as tmp:
+        ds.save(tmp, **_kwargs)
+        ds1 = from_source("file", tmp)
+        assert ds1.metadata("bitsPerValue") == [expected_value] * len(ds)
+
+
 if __name__ == "__main__":
     from earthkit.data.testing import main