CLN: remove unnecessary bits from dtypes.pyx (#55985)

Author: jbrockmendel

Diff for: pandas/_libs/tslibs/ccalendar.pxd

@@ -15,6 +15,6 @@ cpdef int32_t get_day_of_year(int year, int month, int day) noexcept nogil
 cpdef int get_lastbday(int year, int month) noexcept nogil
 cpdef int get_firstbday(int year, int month) noexcept nogil
 
-cdef dict c_MONTH_NUMBERS
+cdef dict c_MONTH_NUMBERS, MONTH_TO_CAL_NUM
 
 cdef int32_t* month_offset

Diff for: pandas/_libs/tslibs/ccalendar.pyx

@@ -38,7 +38,7 @@ MONTHS_FULL = ["", "January", "February", "March", "April", "May", "June",
 MONTH_NUMBERS = {name: num for num, name in enumerate(MONTHS)}
 cdef dict c_MONTH_NUMBERS = MONTH_NUMBERS
 MONTH_ALIASES = {(num + 1): name for num, name in enumerate(MONTHS)}
-MONTH_TO_CAL_NUM = {name: num + 1 for num, name in enumerate(MONTHS)}
+cdef dict MONTH_TO_CAL_NUM = {name: num + 1 for num, name in enumerate(MONTHS)}
 
 DAYS = ["MON", "TUE", "WED", "THU", "FRI", "SAT", "SUN"]
 DAYS_FULL = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday",

Diff for: pandas/_libs/tslibs/dtypes.pyi

@@ -1,14 +1,6 @@
 from enum import Enum
 
-from pandas._libs.tslibs.timedeltas import UnitChoices
-
-# These are not public API, but are exposed in the .pyi file because they
-#  are imported in tests.
-_attrname_to_abbrevs: dict[str, str]
-_period_code_map: dict[str, int]
 OFFSET_TO_PERIOD_FREQSTR: dict[str, str]
-OFFSET_DEPR_FREQSTR: dict[str, str]
-DEPR_ABBREVS: dict[str, UnitChoices]
 
 def periods_per_day(reso: int) -> int: ...
 def periods_per_second(reso: int) -> int: ...

Diff for: pandas/_libs/tslibs/dtypes.pyx

@@ -5,6 +5,7 @@ import warnings
 
 from pandas.util._exceptions import find_stack_level
 
+from pandas._libs.tslibs.ccalendar cimport c_MONTH_NUMBERS
 from pandas._libs.tslibs.np_datetime cimport (
     NPY_DATETIMEUNIT,
     get_conversion_factor,
@@ -46,7 +47,7 @@ cdef class PeriodDtypeBase:
     def _resolution_obj(self) -> "Resolution":
         fgc = self._freq_group_code
         freq_group = FreqGroup(fgc)
-        abbrev = _reverse_period_code_map[freq_group.value].split("-")[0]
+        abbrev = _period_code_to_abbrev[freq_group.value].split("-")[0]
         if abbrev == "B":
             return Resolution.RESO_DAY
         attrname = _abbrev_to_attrnames[abbrev]
@@ -55,7 +56,7 @@ cdef class PeriodDtypeBase:
     @property
     def _freqstr(self) -> str:
         # Will be passed to to_offset in Period._maybe_convert_freq
-        out = _reverse_period_code_map.get(self._dtype_code)
+        out = _period_code_to_abbrev.get(self._dtype_code)
         if self._n == 1:
             return out
         return str(self._n) + out
@@ -150,27 +151,13 @@ _period_code_map = {
     "ns": PeriodDtypeCode.N,       # Nanosecondly
 }
 
-_reverse_period_code_map = {
+cdef dict _period_code_to_abbrev = {
     _period_code_map[key]: key for key in _period_code_map}
 
-# Yearly aliases; careful not to put these in _reverse_period_code_map
-_period_code_map.update({"Y" + key[1:]: _period_code_map[key]
-                         for key in _period_code_map
-                         if key.startswith("Y-")})
-
-_period_code_map.update({
-    "Q": 2000,   # Quarterly - December year end (default quarterly)
-    "Y": PeriodDtypeCode.A,   # Annual
-    "W": 4000,   # Weekly
-    "C": 5000,   # Custom Business Day
-})
-
-cdef set _month_names = {
-    x.split("-")[-1] for x in _period_code_map.keys() if x.startswith("Y-")
-}
+cdef set _month_names = set(c_MONTH_NUMBERS.keys())
 
 # Map attribute-name resolutions to resolution abbreviations
-_attrname_to_abbrevs = {
+cdef dict attrname_to_abbrevs = {
     "year": "Y",
     "quarter": "Q",
     "month": "M",
@@ -182,7 +169,6 @@ _attrname_to_abbrevs = {
     "microsecond": "us",
     "nanosecond": "ns",
 }
-cdef dict attrname_to_abbrevs = _attrname_to_abbrevs
 cdef dict _abbrev_to_attrnames = {v: k for k, v in attrname_to_abbrevs.items()}
 
 OFFSET_TO_PERIOD_FREQSTR: dict = {
@@ -234,7 +220,7 @@ OFFSET_TO_PERIOD_FREQSTR: dict = {
     "YS": "Y",
     "BYS": "Y",
 }
-OFFSET_DEPR_FREQSTR: dict[str, str]= {
+cdef dict c_OFFSET_DEPR_FREQSTR = {
     "M": "ME",
     "Q": "QE",
     "Q-DEC": "QE-DEC",
@@ -277,8 +263,9 @@ OFFSET_DEPR_FREQSTR: dict[str, str]= {
     "A-NOV": "YE-NOV",
 }
 cdef dict c_OFFSET_TO_PERIOD_FREQSTR = OFFSET_TO_PERIOD_FREQSTR
-cdef dict c_OFFSET_DEPR_FREQSTR = OFFSET_DEPR_FREQSTR
-cdef dict c_REVERSE_OFFSET_DEPR_FREQSTR = {v: k for k, v in OFFSET_DEPR_FREQSTR.items()}
+cdef dict c_REVERSE_OFFSET_DEPR_FREQSTR = {
+    v: k for k, v in c_OFFSET_DEPR_FREQSTR.items()
+}
 
 cpdef freq_to_period_freqstr(freq_n, freq_name):
     if freq_n == 1:
@@ -290,7 +277,7 @@ cpdef freq_to_period_freqstr(freq_n, freq_name):
     return freqstr
 
 # Map deprecated resolution abbreviations to correct resolution abbreviations
-DEPR_ABBREVS: dict[str, str]= {
+cdef dict c_DEPR_ABBREVS = {
     "A": "Y",
     "a": "Y",
     "A-DEC": "Y-DEC",
@@ -359,7 +346,6 @@ DEPR_ABBREVS: dict[str, str]= {
     "N": "ns",
     "n": "ns",
 }
-cdef dict c_DEPR_ABBREVS = DEPR_ABBREVS
 
 
 class FreqGroup(Enum):
@@ -406,7 +392,7 @@ class Resolution(Enum):
     @property
     def attr_abbrev(self) -> str:
         # string that we can pass to to_offset
-        return _attrname_to_abbrevs[self.attrname]
+        return attrname_to_abbrevs[self.attrname]
 
     @property
     def attrname(self) -> str:
@@ -450,16 +436,19 @@ class Resolution(Enum):
         >>> Resolution.get_reso_from_freqstr('h') == Resolution.RESO_HR
         True
         """
+        cdef:
+            str abbrev
         try:
-            if freq in DEPR_ABBREVS:
+            if freq in c_DEPR_ABBREVS:
+                abbrev = c_DEPR_ABBREVS[freq]
                 warnings.warn(
                     f"\'{freq}\' is deprecated and will be removed in a future "
-                    f"version. Please use \'{DEPR_ABBREVS.get(freq)}\' "
+                    f"version. Please use \'{abbrev}\' "
                     "instead of \'{freq}\'.",
                     FutureWarning,
                     stacklevel=find_stack_level(),
                 )
-                freq = DEPR_ABBREVS[freq]
+                freq = abbrev
             attr_name = _abbrev_to_attrnames[freq]
         except KeyError:
             # For quarterly and yearly resolutions, we need to chop off
@@ -470,15 +459,16 @@ class Resolution(Enum):
             if split_freq[1] not in _month_names:
                 # i.e. we want e.g. "Q-DEC", not "Q-INVALID"
                 raise
-            if split_freq[0] in DEPR_ABBREVS:
+            if split_freq[0] in c_DEPR_ABBREVS:
+                abbrev = c_DEPR_ABBREVS[split_freq[0]]
                 warnings.warn(
                     f"\'{split_freq[0]}\' is deprecated and will be removed in a "
-                    f"future version. Please use \'{DEPR_ABBREVS.get(split_freq[0])}\' "
+                    f"future version. Please use \'{abbrev}\' "
                     f"instead of \'{split_freq[0]}\'.",
                     FutureWarning,
                     stacklevel=find_stack_level(),
                 )
-                split_freq[0] = DEPR_ABBREVS[split_freq[0]]
+                split_freq[0] = abbrev
             attr_name = _abbrev_to_attrnames[split_freq[0]]
 
         return cls.from_attrname(attr_name)

Diff for: pandas/_libs/tslibs/offsets.pyx

@@ -42,13 +42,13 @@ from pandas._libs.tslibs.util cimport (
 
 from pandas._libs.tslibs.ccalendar import (
     MONTH_ALIASES,
-    MONTH_TO_CAL_NUM,
     int_to_weekday,
     weekday_to_int,
 )
 from pandas.util._exceptions import find_stack_level
 
 from pandas._libs.tslibs.ccalendar cimport (
+    MONTH_TO_CAL_NUM,
     dayofweek,
     get_days_in_month,
     get_firstbday,

Diff for: pandas/_libs/tslibs/parsing.pyx

@@ -51,7 +51,7 @@ from dateutil.tz import (
 
 from pandas._config import get_option
 
-from pandas._libs.tslibs.ccalendar cimport c_MONTH_NUMBERS
+from pandas._libs.tslibs.ccalendar cimport MONTH_TO_CAL_NUM
 from pandas._libs.tslibs.dtypes cimport (
     attrname_to_npy_unit,
     npy_unit_to_attrname,
@@ -623,7 +623,7 @@ cpdef quarter_to_myear(int year, int quarter, str freq):
         raise ValueError("Quarter must be 1 <= q <= 4")
 
     if freq is not None:
-        mnum = c_MONTH_NUMBERS[get_rule_month(freq)] + 1
+        mnum = MONTH_TO_CAL_NUM[get_rule_month(freq)]
         month = (mnum + (quarter - 1) * 3) % 12 + 1
         if month > mnum:
             year -= 1

Diff for: pandas/tests/scalar/period/test_asfreq.py

@@ -1,6 +1,5 @@
 import pytest
 
-from pandas._libs.tslibs.dtypes import _period_code_map
 from pandas._libs.tslibs.period import INVALID_FREQ_ERR_MSG
 from pandas.errors import OutOfBoundsDatetime
 
@@ -828,5 +827,3 @@ def test_asfreq_MS(self):
         msg = "MonthBegin is not supported as period frequency"
         with pytest.raises(TypeError, match=msg):
             Period("2013-01", "MS")
-
-        assert _period_code_map.get("MS") is None

Diff for: pandas/tests/tseries/frequencies/test_freq_code.py

@@ -6,7 +6,6 @@
     Resolution,
     to_offset,
 )
-from pandas._libs.tslibs.dtypes import _attrname_to_abbrevs
 
 import pandas._testing as tm
 
@@ -40,14 +39,9 @@ def test_get_to_timestamp_base(freqstr, exp_freqstr):
     ],
 )
 def test_get_attrname_from_abbrev(freqstr, expected):
-    assert Resolution.get_reso_from_freqstr(freqstr).attrname == expected
-
-
-@pytest.mark.parametrize("freq", ["D", "h", "min", "s", "ms", "us", "ns"])
-def test_get_freq_roundtrip2(freq):
-    obj = Resolution.get_reso_from_freqstr(freq)
-    result = _attrname_to_abbrevs[obj.attrname]
-    assert freq == result
+    reso = Resolution.get_reso_from_freqstr(freqstr)
+    assert reso.attr_abbrev == freqstr
+    assert reso.attrname == expected
 
 
 @pytest.mark.parametrize(