PERF: ints_to_pydatetime

pandas/_libs/tslib.pyx

@@ -15,7 +15,7 @@ PyDateTime_IMPORT
 
 
 cimport numpy as cnp
-from numpy cimport float64_t, int64_t, ndarray, uint8_t
+from numpy cimport float64_t, int64_t, ndarray, uint8_t, intp_t
 import numpy as np
 cnp.import_array()
 
@@ -157,13 +157,15 @@ def ints_to_pydatetime(
         Py_ssize_t i, n = len(arr)
         ndarray[int64_t] trans
         int64_t[:] deltas
-        Py_ssize_t pos
+        intp_t[:] pos
         npy_datetimestruct dts
         object dt, new_tz
         str typ
-        int64_t value, delta, local_value
+        int64_t value, local_value, delta = NPY_NAT  # dummy for delta
         ndarray[object] result = np.empty(n, dtype=object)
         object (*func_create)(int64_t, npy_datetimestruct, tzinfo, object, bint)
+        bint use_utc = False, use_tzlocal = False, use_fixed = False
+        bint use_pytz = False
 
     if box == "date":
         assert (tz is None), "tz should be None when converting to date"
@@ -184,66 +186,45 @@ def ints_to_pydatetime(
         )
 
     if is_utc(tz) or tz is None:
-        for i in range(n):
-            value = arr[i]
-            if value == NPY_NAT:
-                result[i] = <object>NaT
-            else:
-                dt64_to_dtstruct(value, &dts)
-                result[i] = func_create(value, dts, tz, freq, fold)
+        use_utc = True
     elif is_tzlocal(tz):
-        for i in range(n):
-            value = arr[i]
-            if value == NPY_NAT:
-                result[i] = <object>NaT
-            else:
-                # Python datetime objects do not support nanosecond
-                # resolution (yet, PEP 564). Need to compute new value
-                # using the i8 representation.
-                local_value = tz_convert_utc_to_tzlocal(value, tz)
-                dt64_to_dtstruct(local_value, &dts)
-                result[i] = func_create(value, dts, tz, freq, fold)
+        use_tzlocal = True
     else:
         trans, deltas, typ = get_dst_info(tz)
-
-        if typ not in ['pytz', 'dateutil']:
+        if typ not in ["pytz", "dateutil"]:
             # static/fixed; in this case we know that len(delta) == 1
+            use_fixed = True
             delta = deltas[0]
-            for i in range(n):
-                value = arr[i]
-                if value == NPY_NAT:
-                    result[i] = <object>NaT
-                else:
-                    # Adjust datetime64 timestamp, recompute datetimestruct
-                    dt64_to_dtstruct(value + delta, &dts)
-                    result[i] = func_create(value, dts, tz, freq, fold)
+        else:
+            pos = trans.searchsorted(arr, side="right") - 1
+            use_pytz = typ == "pytz"
 
-        elif typ == 'dateutil':
-            # no zone-name change for dateutil tzs - dst etc
-            # represented in single object.
-            for i in range(n):
-                value = arr[i]
-                if value == NPY_NAT:
-                    result[i] = <object>NaT
-                else:
-                    # Adjust datetime64 timestamp, recompute datetimestruct
-                    pos = trans.searchsorted(value, side='right') - 1
-                    dt64_to_dtstruct(value + deltas[pos], &dts)
-                    result[i] = func_create(value, dts, tz, freq, fold)
+    for i in range(n):
+        new_tz = tz
+        value = arr[i]
+
+        if value == NPY_NAT:
+            result[i] = <object>NaT
         else:
-            # pytz
-            for i in range(n):
-                value = arr[i]
-                if value == NPY_NAT:
-                    result[i] = <object>NaT
-                else:
-                    # Adjust datetime64 timestamp, recompute datetimestruct
-                    pos = trans.searchsorted(value, side='right') - 1
-                    # find right representation of dst etc in pytz timezone
-                    new_tz = tz._tzinfos[tz._transition_info[pos]]
+            if use_utc:
+                local_value = value
+            elif use_tzlocal:
+                local_value = tz_convert_utc_to_tzlocal(value, tz)
+            elif use_fixed:
+                local_value = value + delta
+            elif not use_pytz:
+                # i.e. dateutil
+                # no zone-name change for dateutil tzs - dst etc
+                # represented in single object.
+                local_value = value + deltas[pos[i]]
+            else:
+                # pytz
+                # find right representation of dst etc in pytz timezone
+                new_tz = tz._tzinfos[tz._transition_info[pos[i]]]
+                local_value = value + deltas[pos[i]]
 
-                    dt64_to_dtstruct(value + deltas[pos], &dts)
-                    result[i] = func_create(value, dts, new_tz, freq, fold)
+            dt64_to_dtstruct(local_value, &dts)
+            result[i] = func_create(value, dts, new_tz, freq, fold)
 
     return result