194 write method added to NetCDFFieldList method

earthkit/data/readers/netcdf.py

@@ -575,6 +575,9 @@ def to_xarray_multi_from_paths(cls, paths, **kwargs):
             **options,
         )
 
+    def write(self, *args, **kwargs):
+        return self.to_netcdf(*args, **kwargs)
+
 
 class NetCDFFieldListInFiles(NetCDFFieldList):
     pass
@@ -601,15 +604,24 @@ class NetCDFMaskFieldList(NetCDFFieldList, MaskIndex):
     def __init__(self, *args, **kwargs):
         MaskIndex.__init__(self, *args, **kwargs)
 
+    # TODO: Implement this, but discussion required
+    def to_xarray(self, *args, **kwargs):
+        self._not_implemented()
+
 
 class NetCDFMultiFieldList(NetCDFFieldList, MultiIndex):
     def __init__(self, *args, **kwargs):
         MultiIndex.__init__(self, *args, **kwargs)
 
     def to_xarray(self, **kwargs):
-        return NetCDFFieldList.to_xarray_multi_from_paths(
-            [x.path for x in self.indexes], **kwargs
-        )
+        try:
+            return NetCDFFieldList.to_xarray_multi_from_paths(
+                [x.path for x in self.indexes], **kwargs
+            )
+        except AttributeError:
+            # TODO: Implement this, but discussion required
+            #  This catches Multi-MaskFieldLists which cannot be openned in xarray
+            self._not_implemented()
 
 
 class NetCDFFieldListReader(NetCDFFieldListInOneFile, Reader):

tests/netcdf/test_netcdf_output.py

@@ -0,0 +1,65 @@
+#!/usr/bin/env python3
+
+# (C) Copyright 2020 ECMWF.
+#
+# This software is licensed under the terms of the Apache Licence Version 2.0
+# which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+# In applying this licence, ECMWF does not waive the privileges and immunities
+# granted to it by virtue of its status as an intergovernmental organisation
+# nor does it submit to any jurisdiction.
+#
+
+import os
+
+import pytest
+
+from earthkit.data import from_source
+from earthkit.data.core.temporary import temp_file
+from earthkit.data.testing import earthkit_examples_file
+
+
+def test_netcdf_fieldlist_save():
+    ds = from_source("file", earthkit_examples_file("test.nc"))
+    assert len(ds) == 2
+
+    tmp = temp_file()
+    ds.save(tmp.path)
+    assert os.path.exists(tmp.path)
+    r_tmp = from_source("file", tmp.path)
+    assert len(r_tmp) == 2
+
+
+def test_netcdf_fieldlist_subset_save():
+    ds = from_source("file", earthkit_examples_file("test.nc"))
+    assert len(ds) == 2
+    r = ds[1]
+
+    tmp = temp_file()
+    with pytest.raises(NotImplementedError):
+        r.save(tmp.path)
+
+
+def test_netcdf_fieldlist_multi_subset_save():
+    ds1 = from_source("file", earthkit_examples_file("test.nc"))
+    ds2 = from_source("file", earthkit_examples_file("tuv_pl.nc"))
+
+    ds = ds1 + ds2
+    assert len(ds) == 20
+
+    tmp = temp_file()
+    ds.save(tmp.path)
+    assert os.path.exists(tmp.path)
+    r_tmp = from_source("file", tmp.path)
+    assert len(r_tmp) == 20
+
+
+def test_netcdf_fieldlist_multi_subset_save_bad():
+    ds1 = from_source("file", earthkit_examples_file("test.nc"))
+    ds2 = from_source("file", earthkit_examples_file("tuv_pl.nc"))
+
+    ds = ds1 + ds2[1:5]
+    assert len(ds) == 6
+
+    tmp = temp_file()
+    with pytest.raises(NotImplementedError):
+        ds.save(tmp.path)

tests/sources/test_url.py

@@ -15,8 +15,12 @@
 import pytest
 
 from earthkit.data import from_source, settings
-from earthkit.data.core.temporary import temp_directory
-from earthkit.data.testing import earthkit_file, network_off
+from earthkit.data.core.temporary import temp_directory, temp_file
+from earthkit.data.testing import (
+    earthkit_file,
+    earthkit_remote_test_data_file,
+    network_off,
+)
 
 
 @pytest.mark.skipif(  # TODO: fix
@@ -129,6 +133,17 @@ def test_url_part_file_source():
         assert f.read() == b"GRIB7777GRIB7777"
 
 
+def test_url_netcdf_source_save():
+    ds = from_source(
+        "url",
+        earthkit_remote_test_data_file("examples/test.nc"),
+    )
+
+    tmp = temp_file()
+    ds.save(tmp.path)
+    assert os.path.exists(tmp.path)
+
+
 if __name__ == "__main__":
     test_part_url()
     # from earthkit.data.testing import main