feat: Mean() works with TimeDelta(), #761

CHANGELOG.rst

@@ -2,6 +2,7 @@
 -----
 
 * feat: Lowercase the ``null_values`` provided to individual data types, since all comparisons to ``null_values`` are case-insensitive. (#770)
+* feat: :class:`.Mean` works with :class:`.TimeDelta`. (#761)
 * fix: Allow consecutive calls to :meth:`.Table.group_by`. (#765)
 
 1.7.1 - Jan 4, 2023

agate/aggregations/mean.py

@@ -1,7 +1,7 @@
 from agate.aggregations.base import Aggregation
 from agate.aggregations.has_nulls import HasNulls
 from agate.aggregations.sum import Sum
-from agate.data_types import Number
+from agate.data_types import Number, TimeDelta
 from agate.exceptions import DataTypeError
 from agate.warns import warn_null_calculation
 
@@ -18,13 +18,16 @@ def __init__(self, column_name):
         self._sum = Sum(column_name)
 
     def get_aggregate_data_type(self, table):
-        return Number()
+        column = table.columns[self._column_name]
+
+        if isinstance(column.data_type, (Number, TimeDelta)):
+            return column.data_type
 
     def validate(self, table):
         column = table.columns[self._column_name]
 
-        if not isinstance(column.data_type, Number):
-            raise DataTypeError('Mean can only be applied to columns containing Number data.')
+        if not isinstance(column.data_type, (Number, TimeDelta)):
+            raise DataTypeError('Mean can only be applied to columns containing Number or TimeDelta data.')
 
         has_nulls = HasNulls(self._column_name).run(table)
 

tests/test_aggregations.py

@@ -184,11 +184,13 @@ def setUp(self):
         self.table = Table(self.rows, ['test', 'null'], [DateTime(), DateTime()])
 
         self.time_delta_rows = [
-            [datetime.timedelta(seconds=10), None],
-            [datetime.timedelta(seconds=20), None],
+            [datetime.timedelta(seconds=10), datetime.timedelta(seconds=15), None],
+            [datetime.timedelta(seconds=20), None, None],
         ]
 
-        self.time_delta_table = Table(self.time_delta_rows, ['test', 'null'], [TimeDelta(), TimeDelta()])
+        self.time_delta_table = Table(
+            self.time_delta_rows, ['test', 'mixed', 'null'], [TimeDelta(), TimeDelta(), TimeDelta()]
+        )
 
     def test_min(self):
         self.assertIsInstance(Min('test').get_aggregate_data_type(self.table), DateTime)
@@ -216,6 +218,27 @@ def test_max_time_delta(self):
         Max('test').validate(self.time_delta_table)
         self.assertEqual(Max('test').run(self.time_delta_table), datetime.timedelta(0, 20))
 
+    def test_mean(self):
+        with self.assertWarns(NullCalculationWarning):
+            Mean('mixed').validate(self.time_delta_table)
+
+        Mean('test').validate(self.time_delta_table)
+
+        self.assertEqual(Mean('test').run(self.time_delta_table), datetime.timedelta(seconds=15))
+
+    def test_mean_all_nulls(self):
+        self.assertIsNone(Mean('null').run(self.time_delta_table))
+
+    def test_mean_with_nulls(self):
+        warnings.simplefilter('ignore')
+
+        try:
+            Mean('mixed').validate(self.time_delta_table)
+        finally:
+            warnings.resetwarnings()
+
+        self.assertAlmostEqual(Mean('mixed').run(self.time_delta_table), datetime.timedelta(seconds=15))
+
     def test_sum(self):
         self.assertIsInstance(Sum('test').get_aggregate_data_type(self.time_delta_table), TimeDelta)
         Sum('test').validate(self.time_delta_table)