PERF: Timestamp.normalize

asv_bench/benchmarks/tslibs/timestamp.py

@@ -1,17 +1,29 @@
-import datetime
+from datetime import datetime, timedelta, timezone
 
-import dateutil
+from dateutil.tz import gettz, tzlocal, tzutc
 import numpy as np
 import pytz
 
 from pandas import Timestamp
 
+# One case for each type of tzinfo object that has its own code path
+#  in tzconversion code.
+_tzs = [
+    None,
+    pytz.timezone("Europe/Amsterdam"),
+    gettz("US/Central"),
+    pytz.UTC,
+    tzutc(),
+    timezone(timedelta(minutes=60)),
+    tzlocal(),
+]
+
 
 class TimestampConstruction:
     def setup(self):
         self.npdatetime64 = np.datetime64("2020-01-01 00:00:00")
-        self.dttime_unaware = datetime.datetime(2020, 1, 1, 0, 0, 0)
-        self.dttime_aware = datetime.datetime(2020, 1, 1, 0, 0, 0, 0, pytz.UTC)
+        self.dttime_unaware = datetime(2020, 1, 1, 0, 0, 0)
+        self.dttime_aware = datetime(2020, 1, 1, 0, 0, 0, 0, pytz.UTC)
         self.ts = Timestamp("2020-01-01 00:00:00")
 
     def time_parse_iso8601_no_tz(self):
@@ -49,7 +61,6 @@ def time_from_pd_timestamp(self):
 
 
 class TimestampProperties:
-    _tzs = [None, pytz.timezone("Europe/Amsterdam"), pytz.UTC, dateutil.tz.tzutc()]
     _freqs = [None, "B"]
     params = [_tzs, _freqs]
     param_names = ["tz", "freq"]
@@ -110,7 +121,7 @@ def time_weekday_name(self, tz, freq):
 
 
 class TimestampOps:
-    params = [None, "US/Eastern", pytz.UTC, dateutil.tz.tzutc()]
+    params = _tzs
     param_names = ["tz"]
 
     def setup(self, tz):
@@ -148,7 +159,7 @@ def time_ceil(self, tz):
 
 class TimestampAcrossDst:
     def setup(self):
-        dt = datetime.datetime(2016, 3, 27, 1)
+        dt = datetime(2016, 3, 27, 1)
         self.tzinfo = pytz.timezone("CET").localize(dt, is_dst=False).tzinfo
         self.ts2 = Timestamp(dt)
 

pandas/_libs/tslibs/conversion.pxd

@@ -26,3 +26,4 @@ cpdef datetime localize_pydatetime(datetime dt, object tz)
 cdef int64_t cast_from_unit(object ts, str unit) except? -1
 
 cpdef ndarray[int64_t] normalize_i8_timestamps(const int64_t[:] stamps, tzinfo tz)
+cdef int64_t normalize_i8_stamp(int64_t local_val) nogil

pandas/_libs/tslibs/conversion.pyx

@@ -795,14 +795,14 @@ cpdef ndarray[int64_t] normalize_i8_timestamps(const int64_t[:] stamps, tzinfo t
                     result[i] = NPY_NAT
                     continue
                 local_val = stamps[i]
-                result[i] = _normalize_i8_stamp(local_val)
+                result[i] = normalize_i8_stamp(local_val)
     elif is_tzlocal(tz):
         for i in range(n):
             if stamps[i] == NPY_NAT:
                 result[i] = NPY_NAT
                 continue
             local_val = tz_convert_utc_to_tzlocal(stamps[i], tz)
-            result[i] = _normalize_i8_stamp(local_val)
+            result[i] = normalize_i8_stamp(local_val)
     else:
         # Adjust datetime64 timestamp, recompute datetimestruct
         trans, deltas, typ = get_dst_info(tz)
@@ -815,21 +815,21 @@ cpdef ndarray[int64_t] normalize_i8_timestamps(const int64_t[:] stamps, tzinfo t
                     result[i] = NPY_NAT
                     continue
                 local_val = stamps[i] + delta
-                result[i] = _normalize_i8_stamp(local_val)
+                result[i] = normalize_i8_stamp(local_val)
         else:
             pos = trans.searchsorted(stamps, side='right') - 1
             for i in range(n):
                 if stamps[i] == NPY_NAT:
                     result[i] = NPY_NAT
                     continue
                 local_val = stamps[i] + deltas[pos[i]]
-                result[i] = _normalize_i8_stamp(local_val)
+                result[i] = normalize_i8_stamp(local_val)
 
     return result.base  # `.base` to access underlying ndarray
 
 
 @cython.cdivision
-cdef inline int64_t _normalize_i8_stamp(int64_t local_val) nogil:
+cdef inline int64_t normalize_i8_stamp(int64_t local_val) nogil:
     """
     Round the localized nanosecond timestamp down to the previous midnight.
 

pandas/_libs/tslibs/timestamps.pyx

@@ -40,7 +40,7 @@ from pandas._libs.tslibs.conversion cimport (
     _TSObject,
     convert_to_tsobject,
     convert_datetime_to_tsobject,
-    normalize_i8_timestamps,
+    normalize_i8_stamp,
 )
 from pandas._libs.tslibs.fields import get_start_end_field, get_date_name_field
 from pandas._libs.tslibs.nattype cimport NPY_NAT, c_NaT as NaT
@@ -553,6 +553,20 @@ cdef class _Timestamp(ABCTimestamp):
         """
         return ccalendar.get_days_in_month(self.year, self.month)
 
+    # -----------------------------------------------------------------
+    # Transformation Methods
+
+    def normalize(self) -> "Timestamp":
+        """
+        Normalize Timestamp to midnight, preserving tz information.
+        """
+        cdef:
+            local_val = self._maybe_convert_value_to_local()
+            int64_t normalized
+
+        normalized = normalize_i8_stamp(local_val)
+        return Timestamp(normalized).tz_localize(self.tzinfo)
+
     # -----------------------------------------------------------------
     # Pickle Methods
 
@@ -1455,18 +1469,6 @@ default 'raise'
                  self.nanosecond / 3600.0 / 1e+9
                 ) / 24.0)
 
-    def normalize(self):
-        """
-        Normalize Timestamp to midnight, preserving tz information.
-        """
-        cdef:
-            ndarray[int64_t] normalized
-            tzinfo own_tz = self.tzinfo  # could be None
-
-        normalized = normalize_i8_timestamps(
-            np.array([self.value], dtype="i8"), tz=own_tz)
-        return Timestamp(normalized[0]).tz_localize(own_tz)
-
 
 # Aliases
 Timestamp.weekofyear = Timestamp.week