BUG: bug in .at/.loc indexing with a tz-aware columns

closes pandas-dev#15822

Author: Jeff Reback <[email protected]>

Closes pandas-dev#15827 from jreback/at and squashes the following commits:

4fcd2c6 [Jeff Reback] BUG: bug in .at/.loc indexing with a tz-aware columns

Author: jreback

doc/source/whatsnew/v0.20.0.txt

@@ -881,6 +881,7 @@ Bug Fixes
 
 - Compat for 32-bit platforms for ``.qcut/cut``; bins will now be ``int64`` dtype (:issue:`14866`)
 
+- Bug in ``.at`` when selecting from a tz-aware column (:issue:`15822`)
 - Bug in the display of ``.info()`` where a qualifier (+) would always be displayed with a ``MultiIndex`` that contains only non-strings (:issue:`15245`)
 - Bug in ``.replace()`` may result in incorrect dtypes. (:issue:`12747`, :issue:`15765`)
 

pandas/core/frame.py

@@ -1918,7 +1918,16 @@ def get_value(self, index, col, takeable=False):
 
         series = self._get_item_cache(col)
         engine = self.index._engine
-        return engine.get_value(series.get_values(), index)
+
+        try:
+            return engine.get_value(series._values, index)
+        except TypeError:
+
+            # we cannot handle direct indexing
+            # use positional
+            col = self.columns.get_loc(col)
+            index = self.index.get_loc(index)
+            return self.get_value(index, col, takeable=True)
 
     def set_value(self, index, col, value, takeable=False):
         """

pandas/tests/indexing/test_scalar.py

@@ -154,3 +154,18 @@ def test_at_to_fail(self):
         # Check that we get the correct value in the KeyError
         self.assertRaisesRegexp(KeyError, r"\['y'\] not in index",
                                 lambda: df[['x', 'y', 'z']])
+
+    def test_at_with_tz(self):
+        # gh-15822
+        df = DataFrame({'name': ['John', 'Anderson'],
+                        'date': [Timestamp(2017, 3, 13, 13, 32, 56),
+                                 Timestamp(2017, 2, 16, 12, 10, 3)]})
+        df['date'] = df['date'].dt.tz_localize('Asia/Shanghai')
+
+        expected = Timestamp('2017-03-13 13:32:56+0800', tz='Asia/Shanghai')
+
+        result = df.loc[0, 'date']
+        assert result == expected
+
+        result = df.at[0, 'date']
+        assert result == expected