REF: remove libfrequencies

pandas/_libs/tslibs/period.pyx

@@ -74,7 +74,6 @@ from pandas._libs.tslibs.dtypes cimport (
     attrname_to_abbrevs,
 )
 
-from pandas._libs.tslibs.frequencies cimport get_to_timestamp_base
 from pandas._libs.tslibs.parsing cimport get_rule_month
 from pandas._libs.tslibs.parsing import parse_time_string
 from pandas._libs.tslibs.nattype cimport (
@@ -1478,7 +1477,30 @@ class IncompatibleFrequency(ValueError):
     pass
 
 
-cdef class _Period:
+cdef class PeriodMixin:
+    # Methods shared between Period and PeriodArray
+
+    cpdef int _get_to_timestamp_base(self):
+        """
+        Return frequency code group used for base of to_timestamp against
+        frequency code.
+
+        Return day freq code against longer freq than day.
+        Return second freq code against hour between second.
+
+        Returns
+        -------
+        int
+        """
+        base = self._dtype._dtype_code
+        if base < FR_BUS:
+            return FR_DAY
+        elif FR_HR <= base <= FR_SEC:
+            return FR_SEC
+        return base
+
+
+cdef class _Period(PeriodMixin):
 
     cdef readonly:
         int64_t ordinal
@@ -1734,8 +1756,7 @@ cdef class _Period:
             return endpoint - Timedelta(1, 'ns')
 
         if freq is None:
-            base = self._dtype._dtype_code
-            freq = get_to_timestamp_base(base)
+            freq = self._get_to_timestamp_base()
             base = freq
         else:
             freq = self._maybe_convert_freq(freq)

pandas/core/arrays/period.py

@@ -9,17 +9,18 @@
     NaTType,
     Timedelta,
     delta_to_nanoseconds,
-    frequencies as libfrequencies,
     iNaT,
     period as libperiod,
     to_offset,
 )
+from pandas._libs.tslibs.dtypes import FreqGroup
 from pandas._libs.tslibs.fields import isleapyear_arr
 from pandas._libs.tslibs.offsets import Tick, delta_to_tick
 from pandas._libs.tslibs.period import (
     DIFFERENT_FREQ,
     IncompatibleFrequency,
     Period,
+    PeriodMixin,
     get_period_field_arr,
     period_asfreq_arr,
 )
@@ -61,7 +62,7 @@ def f(self):
     return property(f)
 
 
-class PeriodArray(dtl.DatetimeLikeArrayMixin, dtl.DatelikeOps):
+class PeriodArray(PeriodMixin, dtl.DatetimeLikeArrayMixin, dtl.DatelikeOps):
     """
     Pandas ExtensionArray for storing Period data.
 
@@ -440,8 +441,7 @@ def to_timestamp(self, freq=None, how="start"):
                 return (self + self.freq).to_timestamp(how="start") - adjust
 
         if freq is None:
-            base = self.freq._period_dtype_code
-            freq = libfrequencies.get_to_timestamp_base(base)
+            freq = self._get_to_timestamp_base()
             base = freq
         else:
             freq = Period._maybe_convert_freq(freq)
@@ -1027,11 +1027,11 @@ def _range_from_fields(
     if quarter is not None:
         if freq is None:
             freq = to_offset("Q")
-            base = libfrequencies.FreqGroup.FR_QTR
+            base = FreqGroup.FR_QTR
         else:
             freq = to_offset(freq)
             base = libperiod.freq_to_dtype_code(freq)
-            if base != libfrequencies.FreqGroup.FR_QTR:
+            if base != FreqGroup.FR_QTR:
                 raise AssertionError("base must equal FR_QTR")
 
         year, quarter = _make_field_arrays(year, quarter)

pandas/plotting/_matplotlib/timeseries.py

@@ -6,7 +6,7 @@
 import numpy as np
 
 from pandas._libs.tslibs import Period, to_offset
-from pandas._libs.tslibs.frequencies import FreqGroup
+from pandas._libs.tslibs.dtypes import FreqGroup
 from pandas._typing import FrameOrSeriesUnion
 
 from pandas.core.dtypes.generic import (

pandas/tests/tseries/frequencies/test_freq_code.py

@@ -1,18 +1,20 @@
 import pytest
 
-from pandas._libs.tslibs import Resolution, to_offset
+from pandas._libs.tslibs import Period, Resolution, to_offset
 from pandas._libs.tslibs.dtypes import _attrname_to_abbrevs
-from pandas._libs.tslibs.frequencies import get_to_timestamp_base
 
 
 @pytest.mark.parametrize(
     "freqstr,exp_freqstr",
     [("D", "D"), ("W", "D"), ("M", "D"), ("S", "S"), ("T", "S"), ("H", "S")],
 )
 def test_get_to_timestamp_base(freqstr, exp_freqstr):
-    left_code = to_offset(freqstr)._period_dtype_code
+    off = to_offset(freqstr)
+    per = Period._from_ordinal(1, off)
     exp_code = to_offset(exp_freqstr)._period_dtype_code
-    assert get_to_timestamp_base(left_code) == exp_code
+
+    result_code = per._get_to_timestamp_base()
+    assert result_code == exp_code
 
 
 @pytest.mark.parametrize(

pandas/tests/tslibs/test_api.py

@@ -11,7 +11,6 @@ def test_namespace():
         "conversion",
         "dtypes",
         "fields",
-        "frequencies",
         "nattype",
         "np_datetime",
         "offsets",

setup.py

@@ -319,7 +319,6 @@ class CheckSDist(sdist_class):
         "pandas/_libs/tslibs/conversion.pyx",
         "pandas/_libs/tslibs/fields.pyx",
         "pandas/_libs/tslibs/offsets.pyx",
-        "pandas/_libs/tslibs/frequencies.pyx",
         "pandas/_libs/tslibs/resolution.pyx",
         "pandas/_libs/tslibs/parsing.pyx",
         "pandas/_libs/tslibs/tzconversion.pyx",
@@ -615,7 +614,6 @@ def srcpath(name=None, suffix=".pyx", subdir="src"):
         "pyxfile": "_libs/tslibs/fields",
         "depends": tseries_depends,
     },
-    "_libs.tslibs.frequencies": {"pyxfile": "_libs/tslibs/frequencies"},
     "_libs.tslibs.nattype": {"pyxfile": "_libs/tslibs/nattype"},
     "_libs.tslibs.np_datetime": {
         "pyxfile": "_libs/tslibs/np_datetime",