Refactored rounding in DatetimeIndex to use rounding function exported from timestamps

Author: cbertinato

pandas/core/indexes/datetimelike.py

@@ -36,6 +36,7 @@
 from pandas._libs import lib, iNaT, NaT
 from pandas._libs.tslibs.period import Period
 from pandas._libs.tslibs.timedeltas import delta_to_nanoseconds
+from pandas._libs.tslibs.timestamps import round_ns
 
 from pandas.core.indexes.base import Index, _index_shared_docs
 from pandas.util._decorators import Appender, cache_readonly
@@ -91,33 +92,34 @@ class TimelikeOps(object):
 
     def _round(self, freq, rounder):
 
-        from pandas.tseries.frequencies import to_offset
-        unit = to_offset(freq).nanos
+        # from pandas.tseries.frequencies import to_offset
+        # unit = to_offset(freq).nanos
         # round the local times
         values = _ensure_datetimelike_to_i8(self)
 
-        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) * (1 / float(unit))))
-                      .astype('i8'))
-        else:
-            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'))
-
+        # 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) * (1 / float(unit))))
+        #               .astype('i8'))
+        # else:
+        #     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 = round_ns(values, rounder, freq)
         result = self._maybe_mask_results(result, fill_value=NaT)
 
         attribs = self._get_attributes_dict()