BUG: Avoid casting to double type unnecessarily when setting values in time delta column

Author: icexelloss

pandas/core/internals/blocks.py

@@ -2104,9 +2104,9 @@ def _box_func(self):
     def _can_hold_element(self, element):
         tipo = maybe_infer_dtype_type(element)
         if tipo is not None:
-            return issubclass(tipo.type, np.timedelta64)
+            return issubclass(tipo.type, (np.timedelta64, np.int64))
         return is_integer(element) or isinstance(
-            element, (timedelta, np.timedelta64))
+            element, (timedelta, np.timedelta64, np.int64))
 
     def fillna(self, value, **kwargs):
 

pandas/tests/indexing/test_timedelta.py

@@ -80,3 +80,17 @@ def test_numpy_timedelta_scalar_indexing(self, start, stop,
         result = s.loc[slice(start, stop)]
         expected = s.iloc[expected_slice]
         tm.assert_series_equal(result, expected)
+
+    def test_set_dataframe_column_by_index(self):
+        dt1 = pd.Timedelta(0)
+        dt2 = pd.Timedelta(28767471428571405)
+
+        df = pd.DataFrame({'dt': pd.Series([dt1, dt2])})
+        s = pd.Series([dt1])
+
+        value_before = df['dt'].iloc[1].value
+
+        df.loc[[True, False]] = s
+
+        value_after = df['dt'].iloc[1].value
+        assert value_before == value_after