Fix dataframe (de)serialization

param/__init__.py

@@ -1567,14 +1567,16 @@ def _validate(self, val):
     def serialize(cls, value):
         if value is None:
             return 'null'
-        return value.to_dict('records')
+        import json
+        return json.loads(value.to_json(date_format='iso'))
 
     @classmethod
     def deserialize(cls, value):
         if value == 'null':
             return None
-        from pandas import DataFrame as pdDFrame
-        return pdDFrame(value)
+        import json
+        import pandas as pd
+        return pd.read_json(json.dumps(value))
 
 
 class Series(ClassSelector):

tests/API1/testjsonserialization.py

@@ -42,7 +42,7 @@ class TestSet(param.Parameterized):
     __test__ = False
 
     numpy_params = ['r','y']
-    pandas_params = ['s','t','u','z']
+    pandas_params = ['s','t','u','z','ab','ac']
     conditionally_unsafe = ['f', 'o']
 
     a = param.Integer(default=5, doc='Example doc', bounds=(2,30), inclusive_bounds=(True, False))
@@ -73,6 +73,12 @@ class TestSet(param.Parameterized):
     y = None if np is None else param.Array(default=None)
     z = None if pd is None else param.DataFrame(default=None, allow_None=True)
     aa = param.Tuple(default=None, allow_None=True, length=1)
+    ab = None if pd is None else param.DataFrame(default=pd.DataFrame(
+         {'A':[datetime.datetime(year,1,1) for year in range(2020,2023)], 'B':[1.1,2.2,3.3]}),
+         columns=(1,4), rows=(2,5))
+    ac = None if pd is None else param.DataFrame(default=pd.DataFrame(
+         [[1,2,3],[4,5,6],[7,8,9]]),
+         columns=(1,4), rows=(2,5))
 
 
 test = TestSet(a=29)
@@ -186,13 +192,22 @@ def test_numpy_instance_serialization(self):
 
     @pd_skip
     def test_pandas_instance_serialization(self):
+        from pandas.api.types import is_datetime64_any_dtype as is_datetime
         serialized = test.param.serialize_parameters(subset=test.pandas_params, mode=self.mode)
         deserialized = TestSet.param.deserialize_parameters(serialized, mode=self.mode)
         for pname in test.pandas_params:
             if getattr(test, pname) is None:
                 self.assertTrue(deserialized[pname] is None)
             else:
-                self.assertTrue(getattr(test, pname).equals(deserialized[pname]))
+                test_df = getattr(test, pname)
+                deser_df = deserialized[pname].copy()
+
+                date_cols = [c for c in test_df.columns if is_datetime(test_df[c])]
+                for c in date_cols:
+                    src_tz = test_df.loc[0, c].tz
+                    deser_df[c] = pd.to_datetime(deser_df[c]).dt.tz_convert(src_tz)
+
+                self.assertTrue(test_df.equals(deser_df))