Merge pull request #2688 from sfinkens/fix-time-parameters-decoding

Decode time parameters in CF Reader

satpy/cf/decoding.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (c) 2023 Satpy developers
+#
+# This file is part of satpy.
+#
+# satpy is free software: you can redistribute it and/or modify it under the
+# terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# satpy is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# satpy.  If not, see <http://www.gnu.org/licenses/>.
+"""CF decoding."""
+import copy
+import json
+from datetime import datetime
+
+
+def decode_attrs(attrs):
+    """Decode CF-encoded attributes to Python object.
+
+    Converts timestamps to datetime and strings starting with "{" to
+    dictionary.
+
+    Args:
+        attrs (dict): Attributes to be decoded
+
+    Returns (dict): Decoded attributes
+    """
+    attrs = copy.deepcopy(attrs)
+    _decode_dict_type_attrs(attrs)
+    _decode_timestamps(attrs)
+    return attrs
+
+
+def _decode_dict_type_attrs(attrs):
+    for key, val in attrs.items():
+        attrs[key] = _str2dict(val)
+
+
+def _str2dict(val):
+    """Convert string to dictionary."""
+    if isinstance(val, str) and val.startswith("{"):
+        val = json.loads(val, object_hook=_datetime_parser_json)
+    return val
+
+
+def _decode_timestamps(attrs):
+    for key, value in attrs.items():
+        timestamp = _str2datetime(value)
+        if timestamp:
+            attrs[key] = timestamp
+
+
+def _datetime_parser_json(json_dict):
+    """Traverse JSON dictionary and parse timestamps."""
+    for key, value in json_dict.items():
+        timestamp = _str2datetime(value)
+        if timestamp:
+            json_dict[key] = timestamp
+    return json_dict
+
+
+def _str2datetime(string):
+    """Convert string to datetime object."""
+    try:
+        return datetime.fromisoformat(string)
+    except (TypeError, ValueError):
+        return None

satpy/readers/satpy_cf_nc.py

@@ -177,12 +177,12 @@
 
 """
 import itertools
-import json
 import logging
 
 import xarray as xr
 from pyresample import AreaDefinition
 
+import satpy.cf.decoding
 from satpy.dataset.dataid import WavelengthRange
 from satpy.readers.file_handlers import BaseFileHandler
 from satpy.utils import get_legacy_chunk_size
@@ -311,9 +311,7 @@ def get_dataset(self, ds_id, ds_info):
         if name != ds_id["name"]:
             data = data.rename(ds_id["name"])
         data.attrs.update(nc.attrs)  # For now add global attributes to all datasets
-        if "orbital_parameters" in data.attrs:
-            data.attrs["orbital_parameters"] = _str2dict(data.attrs["orbital_parameters"])
-
+        data.attrs = satpy.cf.decoding.decode_attrs(data.attrs)
         return data
 
     def get_area_def(self, dataset_id):
@@ -327,10 +325,3 @@ def get_area_def(self, dataset_id):
             # with the yaml_reader NotImplementedError is raised.
             logger.debug("No AreaDefinition to load from nc file. Falling back to SwathDefinition.")
             raise NotImplementedError
-
-
-def _str2dict(val):
-    """Convert string to dictionary."""
-    if isinstance(val, str):
-        val = json.loads(val)
-    return val

satpy/tests/cf_tests/test_decoding.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (c) 2023 Satpy developers
+#
+# This file is part of satpy.
+#
+# satpy is free software: you can redistribute it and/or modify it under the
+# terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# satpy is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# satpy.  If not, see <http://www.gnu.org/licenses/>.
+"""Tests for CF decoding."""
+from datetime import datetime
+
+import pytest
+
+import satpy.cf.decoding
+
+
+class TestDecodeAttrs:
+    """Test decoding of CF-encoded attributes."""
+
+    @pytest.fixture()
+    def attrs(self):
+        """Get CF-encoded attributes."""
+        return {
+            "my_integer": 0,
+            "my_float": 0.0,
+            "my_list": [1, 2, 3],
+            "my_timestamp1": "2000-01-01",
+            "my_timestamp2": "2000-01-01 12:15:33",
+            "my_timestamp3": "2000-01-01 12:15:33.123456",
+            "my_dict": '{"a": {"b": [1, 2, 3]}, "c": {"d": "2000-01-01 12:15:33.123456"}}'
+        }
+
+    @pytest.fixture()
+    def expected(self):
+        """Get expected decoded results."""
+        return {
+            "my_integer": 0,
+            "my_float": 0.0,
+            "my_list": [1, 2, 3],
+            "my_timestamp1": datetime(2000, 1, 1),
+            "my_timestamp2": datetime(2000, 1, 1, 12, 15, 33),
+            "my_timestamp3": datetime(2000, 1, 1, 12, 15, 33, 123456),
+            "my_dict": {"a": {"b": [1, 2, 3]},
+                        "c": {"d": datetime(2000, 1, 1, 12, 15, 33, 123456)}}
+        }
+
+    def test_decoding(self, attrs, expected):
+        """Test decoding of CF-encoded attributes."""
+        res = satpy.cf.decoding.decode_attrs(attrs)
+        assert res == expected
+
+    def test_decoding_doesnt_modify_original(self, attrs):
+        """Test that decoding doesn't modify the original attributes."""
+        satpy.cf.decoding.decode_attrs(attrs)
+        assert isinstance(attrs["my_dict"], str)