infer_freq handle non-nano (#47126)

* infer_freq handle non-nano

* remove unused import

Author: jbrockmendel

pandas/_libs/tslibs/__init__.py

@@ -26,11 +26,16 @@
     "BaseOffset",
     "tz_compare",
     "is_unitless",
+    "get_unit_from_dtype",
+    "periods_per_day",
 ]
 
 from pandas._libs.tslibs import dtypes
 from pandas._libs.tslibs.conversion import localize_pydatetime
-from pandas._libs.tslibs.dtypes import Resolution
+from pandas._libs.tslibs.dtypes import (
+    Resolution,
+    periods_per_day,
+)
 from pandas._libs.tslibs.nattype import (
     NaT,
     NaTType,
@@ -41,6 +46,7 @@
     OutOfBoundsDatetime,
     OutOfBoundsTimedelta,
     is_unitless,
+    py_get_unit_from_dtype as get_unit_from_dtype,
 )
 from pandas._libs.tslibs.offsets import (
     BaseOffset,

pandas/_libs/tslibs/dtypes.pxd

@@ -5,7 +5,7 @@ from pandas._libs.tslibs.np_datetime cimport NPY_DATETIMEUNIT
 
 cdef str npy_unit_to_abbrev(NPY_DATETIMEUNIT unit)
 cdef NPY_DATETIMEUNIT freq_group_code_to_npy_unit(int freq) nogil
-cdef int64_t periods_per_day(NPY_DATETIMEUNIT reso=*) except? -1
+cpdef int64_t periods_per_day(NPY_DATETIMEUNIT reso=*) except? -1
 cdef int64_t periods_per_second(NPY_DATETIMEUNIT reso) except? -1
 
 cdef dict attrname_to_abbrevs

pandas/_libs/tslibs/dtypes.pyi

@@ -5,6 +5,8 @@ from enum import Enum
 _attrname_to_abbrevs: dict[str, str]
 _period_code_map: dict[str, int]
 
+def periods_per_day(reso: int) -> int: ...
+
 class PeriodDtypeBase:
     _dtype_code: int  # PeriodDtypeCode
 

pandas/_libs/tslibs/dtypes.pyx

@@ -318,7 +318,7 @@ cdef NPY_DATETIMEUNIT freq_group_code_to_npy_unit(int freq) nogil:
 
 
 # TODO: use in _matplotlib.converter?
-cdef int64_t periods_per_day(NPY_DATETIMEUNIT reso=NPY_DATETIMEUNIT.NPY_FR_ns) except? -1:
+cpdef int64_t periods_per_day(NPY_DATETIMEUNIT reso=NPY_DATETIMEUNIT.NPY_FR_ns) except? -1:
     """
     How many of the given time units fit into a single day?
     """

pandas/_libs/tslibs/fields.pyi

@@ -4,6 +4,7 @@ from pandas._typing import npt
 
 def build_field_sarray(
     dtindex: npt.NDArray[np.int64],  # const int64_t[:]
+    reso: int,  # NPY_DATETIMEUNIT
 ) -> np.ndarray: ...
 def month_position_check(fields, weekdays) -> str | None: ...
 def get_date_name_field(
@@ -33,7 +34,7 @@ def isleapyear_arr(
 ) -> npt.NDArray[np.bool_]: ...
 def build_isocalendar_sarray(
     dtindex: npt.NDArray[np.int64],  # const int64_t[:]
-    reso: int = ...,  # NPY_DATETIMEUNIT
+    reso: int,  # NPY_DATETIMEUNIT
 ) -> np.ndarray: ...
 def _get_locale_names(name_type: str, locale: str | None = ...): ...
 

pandas/_libs/tslibs/fields.pyx

@@ -45,7 +45,6 @@ from pandas._libs.tslibs.nattype cimport NPY_NAT
 from pandas._libs.tslibs.np_datetime cimport (
     NPY_DATETIMEUNIT,
     NPY_FR_ns,
-    dt64_to_dtstruct,
     get_unit_from_dtype,
     npy_datetimestruct,
     pandas_datetime_to_datetimestruct,
@@ -56,7 +55,7 @@ from pandas._libs.tslibs.np_datetime cimport (
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def build_field_sarray(const int64_t[:] dtindex):
+def build_field_sarray(const int64_t[:] dtindex, NPY_DATETIMEUNIT reso):
     """
     Datetime as int64 representation to a structured array of fields
     """
@@ -86,7 +85,7 @@ def build_field_sarray(const int64_t[:] dtindex):
     mus = out['u']
 
     for i in range(count):
-        dt64_to_dtstruct(dtindex[i], &dts)
+        pandas_datetime_to_datetimestruct(dtindex[i], reso, &dts)
         years[i] = dts.year
         months[i] = dts.month
         days[i] = dts.day
@@ -565,7 +564,7 @@ cpdef isleapyear_arr(ndarray years):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def build_isocalendar_sarray(const int64_t[:] dtindex, NPY_DATETIMEUNIT reso=NPY_FR_ns):
+def build_isocalendar_sarray(const int64_t[:] dtindex, NPY_DATETIMEUNIT reso):
     """
     Given a int64-based datetime array, return the ISO 8601 year, week, and day
     as a structured array.

pandas/core/arrays/datetimelike.py

@@ -35,6 +35,7 @@
     Tick,
     Timestamp,
     delta_to_nanoseconds,
+    get_unit_from_dtype,
     iNaT,
     ints_to_pydatetime,
     ints_to_pytimedelta,
@@ -44,7 +45,6 @@
     RoundTo,
     round_nsint64,
 )
-from pandas._libs.tslibs.np_datetime import py_get_unit_from_dtype
 from pandas._libs.tslibs.timestamps import integer_op_not_supported
 from pandas._typing import (
     ArrayLike,
@@ -1807,7 +1807,7 @@ class TimelikeOps(DatetimeLikeArrayMixin):
 
     @cache_readonly
     def _reso(self) -> int:
-        return py_get_unit_from_dtype(self._ndarray.dtype)
+        return get_unit_from_dtype(self._ndarray.dtype)
 
     def __array_ufunc__(self, ufunc: np.ufunc, method: str, *inputs, **kwargs):
         if (

pandas/tests/tseries/frequencies/test_inference.py

@@ -22,6 +22,10 @@
     period_range,
 )
 import pandas._testing as tm
+from pandas.core.arrays import (
+    DatetimeArray,
+    TimedeltaArray,
+)
 from pandas.core.tools.datetimes import to_datetime
 
 import pandas.tseries.frequencies as frequencies
@@ -506,3 +510,15 @@ def test_ms_vs_capital_ms():
 def test_infer_freq_warn_deprecated():
     with tm.assert_produces_warning(FutureWarning):
         frequencies.infer_freq(date_range(2022, periods=3), warn=False)
+
+
+def test_infer_freq_non_nano():
+    arr = np.arange(10).astype(np.int64).view("M8[s]")
+    dta = DatetimeArray._simple_new(arr, dtype=arr.dtype)
+    res = frequencies.infer_freq(dta)
+    assert res == "S"
+
+    arr2 = arr.view("m8[ms]")
+    tda = TimedeltaArray._simple_new(arr2, dtype=arr2.dtype)
+    res2 = frequencies.infer_freq(tda)
+    assert res2 == "L"

pandas/tests/tslibs/test_api.py

@@ -51,6 +51,8 @@ def test_namespace():
         "to_offset",
         "tz_compare",
         "is_unitless",
+        "get_unit_from_dtype",
+        "periods_per_day",
     ]
 
     expected = set(submodules + api)

pandas/tseries/frequencies.py

@@ -7,6 +7,8 @@
 from pandas._libs.algos import unique_deltas
 from pandas._libs.tslibs import (
     Timestamp,
+    get_unit_from_dtype,
+    periods_per_day,
     tz_convert_from_utc,
 )
 from pandas._libs.tslibs.ccalendar import (
@@ -37,17 +39,13 @@
     is_period_dtype,
     is_timedelta64_dtype,
 )
-from pandas.core.dtypes.generic import ABCSeries
+from pandas.core.dtypes.generic import (
+    ABCIndex,
+    ABCSeries,
+)
 
 from pandas.core.algorithms import unique
 
-_ONE_MICRO = 1000
-_ONE_MILLI = _ONE_MICRO * 1000
-_ONE_SECOND = _ONE_MILLI * 1000
-_ONE_MINUTE = 60 * _ONE_SECOND
-_ONE_HOUR = 60 * _ONE_MINUTE
-_ONE_DAY = 24 * _ONE_HOUR
-
 # ---------------------------------------------------------------------
 # Offset names ("time rules") and related functions
 
@@ -213,6 +211,18 @@ def __init__(self, index, warn: bool = True) -> None:
         self.index = index
         self.i8values = index.asi8
 
+        # For get_unit_from_dtype we need the dtype to the underlying ndarray,
+        #  which for tz-aware is not the same as index.dtype
+        if isinstance(index, ABCIndex):
+            # error: Item "ndarray[Any, Any]" of "Union[ExtensionArray,
+            # ndarray[Any, Any]]" has no attribute "_ndarray"
+            self._reso = get_unit_from_dtype(
+                index._data._ndarray.dtype  # type: ignore[union-attr]
+            )
+        else:
+            # otherwise we have DTA/TDA
+            self._reso = get_unit_from_dtype(index._ndarray.dtype)
+
         # This moves the values, which are implicitly in UTC, to the
         # the timezone so they are in local time
         if hasattr(index, "tz"):
@@ -266,7 +276,8 @@ def get_freq(self) -> str | None:
             return None
 
         delta = self.deltas[0]
-        if delta and _is_multiple(delta, _ONE_DAY):
+        ppd = periods_per_day(self._reso)
+        if delta and _is_multiple(delta, ppd):
             return self._infer_daily_rule()
 
         # Business hourly, maybe. 17: one day / 65: one weekend
@@ -280,36 +291,41 @@ def get_freq(self) -> str | None:
             return None
 
         delta = self.deltas_asi8[0]
-        if _is_multiple(delta, _ONE_HOUR):
+        pph = ppd // 24
+        ppm = pph // 60
+        pps = ppm // 60
+        if _is_multiple(delta, pph):
             # Hours
-            return _maybe_add_count("H", delta / _ONE_HOUR)
-        elif _is_multiple(delta, _ONE_MINUTE):
+            return _maybe_add_count("H", delta / pph)
+        elif _is_multiple(delta, ppm):
             # Minutes
-            return _maybe_add_count("T", delta / _ONE_MINUTE)
-        elif _is_multiple(delta, _ONE_SECOND):
+            return _maybe_add_count("T", delta / ppm)
+        elif _is_multiple(delta, pps):
             # Seconds
-            return _maybe_add_count("S", delta / _ONE_SECOND)
-        elif _is_multiple(delta, _ONE_MILLI):
+            return _maybe_add_count("S", delta / pps)
+        elif _is_multiple(delta, (pps // 1000)):
             # Milliseconds
-            return _maybe_add_count("L", delta / _ONE_MILLI)
-        elif _is_multiple(delta, _ONE_MICRO):
+            return _maybe_add_count("L", delta / (pps // 1000))
+        elif _is_multiple(delta, (pps // 1_000_000)):
             # Microseconds
-            return _maybe_add_count("U", delta / _ONE_MICRO)
+            return _maybe_add_count("U", delta / (pps // 1_000_000))
         else:
             # Nanoseconds
             return _maybe_add_count("N", delta)
 
     @cache_readonly
     def day_deltas(self):
-        return [x / _ONE_DAY for x in self.deltas]
+        ppd = periods_per_day(self._reso)
+        return [x / ppd for x in self.deltas]
 
     @cache_readonly
     def hour_deltas(self):
-        return [x / _ONE_HOUR for x in self.deltas]
+        pph = periods_per_day(self._reso) // 24
+        return [x / pph for x in self.deltas]
 
     @cache_readonly
     def fields(self) -> np.ndarray:  # structured array of fields
-        return build_field_sarray(self.i8values)
+        return build_field_sarray(self.i8values, reso=self._reso)
 
     @cache_readonly
     def rep_stamp(self):
@@ -360,7 +376,8 @@ def _infer_daily_rule(self) -> str | None:
         return None
 
     def _get_daily_rule(self) -> str | None:
-        days = self.deltas[0] / _ONE_DAY
+        ppd = periods_per_day(self._reso)
+        days = self.deltas[0] / ppd
         if days % 7 == 0:
             # Weekly
             wd = int_to_weekday[self.rep_stamp.weekday()]
@@ -403,7 +420,8 @@ def _is_business_daily(self) -> bool:
         # probably business daily, but need to confirm
         first_weekday = self.index[0].weekday()
         shifts = np.diff(self.index.asi8)
-        shifts = np.floor_divide(shifts, _ONE_DAY)
+        ppd = periods_per_day(self._reso)
+        shifts = np.floor_divide(shifts, ppd)
         weekdays = np.mod(first_weekday + np.cumsum(shifts), 7)
 
         return bool(