Added tests and fix for DatetimeIndex

Author: cbertinato

pandas/core/indexes/datetimelike.py

@@ -95,18 +95,29 @@ def _round(self, freq, rounder):
         unit = to_offset(freq).nanos
         # round the local times
         values = _ensure_datetimelike_to_i8(self)
-        if unit < 1000 and unit % 1000 != 0:
+
+        if unit < 1000:
             # for nano rounding, work with the last 6 digits separately
             # due to float precision
             buff = 1000000
             result = (buff * (values // buff) + unit *
-                      (rounder((values % buff) / float(unit))).astype('i8'))
-        elif unit >= 1000 and unit % 1000 != 0:
-            msg = 'Precision will be lost using frequency: {}'
-            warnings.warn(msg.format(freq))
-            result = (unit * rounder(values / float(unit)).astype('i8'))
+                      (rounder((values % buff) * (1 / float(unit))))
+                      .astype('i8'))
         else:
-            result = (unit * rounder(values / float(unit)).astype('i8'))
+            if unit % 1000 != 0:
+                msg = 'Precision will be lost using frequency: {}'
+                warnings.warn(msg.format(freq))
+
+            # GH19206
+            # to deal with round-off when unit is large
+            if unit >= 1e9:
+                divisor = 10 ** int(np.log10(unit / 1e7))
+            else:
+                divisor = 10
+
+            result = (unit * rounder((values * (divisor / float(unit))) /
+                                     divisor).astype('i8'))
+
         result = self._maybe_mask_results(result, fill_value=NaT)
 
         attribs = self._get_attributes_dict()

pandas/tests/indexes/datetimes/test_ops.py

@@ -144,7 +144,40 @@ def test_numpy_minmax(self):
             tm.assert_raises_regex(
                 ValueError, errmsg, np.argmax, dr, out=0)
 
-    def test_round(self):
+    @pytest.mark.parametrize('test_input, rounder, freq, expected', [
+        # GH 14440 & 15578
+        ('2016-10-17 12:00:00.0015', 'round', 'ms',
+         '2016-10-17 12:00:00.002000'),
+        ('2016-10-17 12:00:00.0015', 'round', 'us',
+         '2016-10-17 12:00:00.0015'),
+        ('2016-10-17 12:00:00.0015', 'round', 'ns',
+         '2016-10-17 12:00:00.0015'),
+        ('2016-10-17 12:00:00.00149', 'round', 'ms',
+         '2016-10-17 12:00:00.001000'),
+        ('2016-10-17 12:00:00.001501031', 'round', '10ns',
+         '2016-10-17 12:00:00.001501030'),
+        # GH 19206 - times far in the future and past rounding incorrectly
+        ('2117-01-01 00:00:45', 'floor', '15s', '2117-01-01 00:00:45'),
+        ('2117-01-01 00:00:45', 'ceil', '15s', '2117-01-01 00:00:45'),
+        ('2117-01-01 00:00:45.000000012', 'floor', '10ns',
+         '2117-01-01 00:00:45.000000010'),
+        ('1823-01-01 00:00:01', 'floor', '1s', '1823-01-01 00:00:01'),
+        ('1823-01-01 00:00:01', 'ceil', '1s', '1823-01-01 00:00:01'),
+        ('1823-01-01 00:00:01.000000012', 'floor', '10ns',
+         '1823-01-01 00:00:01.000000010'),
+        ('1823-01-01 00:00:01.000000012', 'ceil', '10ns',
+         '1823-01-01 00:00:01.000000020')
+    ])
+    # @pytest.mark.parametrize('tz', tz)
+    def test_round_ops(self, test_input, rounder, freq, expected):
+        for tz in self.tz:
+            index = pd.DatetimeIndex([test_input], tz=tz)
+            func = getattr(index, rounder)
+            result = func(freq)
+            expect = pd.DatetimeIndex([expected], tz=tz)
+            tm.assert_index_equal(result, expect)
+
+    def test_round_raises(self):
         for tz in self.tz:
             rng = pd.date_range(start='2016-01-01', periods=5,
                                 freq='30Min', tz=tz)
@@ -172,25 +205,6 @@ def test_round(self):
             tm.assert_raises_regex(ValueError, msg, rng.round, freq='M')
             tm.assert_raises_regex(ValueError, msg, elt.round, freq='M')
 
-            # GH 14440 & 15578
-            index = pd.DatetimeIndex(['2016-10-17 12:00:00.0015'], tz=tz)
-            result = index.round('ms')
-            expected = pd.DatetimeIndex(['2016-10-17 12:00:00.002000'], tz=tz)
-            tm.assert_index_equal(result, expected)
-
-            for freq in ['us', 'ns']:
-                tm.assert_index_equal(index, index.round(freq))
-
-            index = pd.DatetimeIndex(['2016-10-17 12:00:00.00149'], tz=tz)
-            result = index.round('ms')
-            expected = pd.DatetimeIndex(['2016-10-17 12:00:00.001000'], tz=tz)
-            tm.assert_index_equal(result, expected)
-
-            index = pd.DatetimeIndex(['2016-10-17 12:00:00.001501031'])
-            result = index.round('10ns')
-            expected = pd.DatetimeIndex(['2016-10-17 12:00:00.001501030'])
-            tm.assert_index_equal(result, expected)
-
             with tm.assert_produces_warning():
                 ts = '2016-10-17 12:00:00.001501031'
                 pd.DatetimeIndex([ts]).round('1010ns')