REF: de-duplicate hard-coded unit code

pandas/_libs/tslib.pyx

@@ -243,7 +243,7 @@ def array_with_unit_to_datetime(
             )
         return result, tz
 
-    m, p = precision_from_unit(unit)
+    m, _ = precision_from_unit(unit)
 
     if is_raise:
         # try a quick conversion to i8/f8

pandas/_libs/tslibs/dtypes.pxd

@@ -1,7 +1,13 @@
+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 dict attrname_to_abbrevs
 
 cdef enum c_FreqGroup:
-    # Mirrors FreqGroup in the .pxy file
+    # Mirrors FreqGroup in the .pyx file
     FR_ANN = 1000
     FR_QTR = 2000
     FR_MTH = 3000
@@ -17,6 +23,20 @@ cdef enum c_FreqGroup:
     FR_UND = -10000  # undefined
 
 
+cdef enum c_Resolution:
+    # Mirrors Resolution in the .pyx file
+    RESO_NS = 0
+    RESO_US = 1
+    RESO_MS = 2
+    RESO_SEC = 3
+    RESO_MIN = 4
+    RESO_HR = 5
+    RESO_DAY = 6
+    RESO_MTH = 7
+    RESO_QTR = 8
+    RESO_YR = 9
+
+
 cdef enum PeriodDtypeCode:
     # Annual freqs with various fiscal year ends.
     # eg, 2005 for A_FEB runs Mar 1, 2004 to Feb 28, 2005

pandas/_libs/tslibs/dtypes.pyi

@@ -2,6 +2,8 @@ from enum import Enum
 
 from pandas._libs.tslibs.offsets import BaseOffset
 
+# 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]
 
@@ -10,13 +12,11 @@ class PeriodDtypeBase:
 
     # actually __cinit__
     def __new__(cls, code: int): ...
-    def freq_group_code(self) -> int: ...
-    def date_offset(self) -> BaseOffset: ...
-    @classmethod
-    def from_date_offset(cls, offset: BaseOffset) -> PeriodDtypeBase: ...
+    def _freq_group_code(self) -> int: ...
     @property
-    def resolution(self) -> Resolution: ...
+    def _resolution_obj(self) -> Resolution: ...
     def _get_to_timestamp_base(self) -> int: ...
+    def _freqstr(self) -> str: ...
 
 class FreqGroup(Enum):
     FR_ANN: int
@@ -33,7 +33,7 @@ class FreqGroup(Enum):
     FR_NS: int
     FR_UND: int
     @staticmethod
-    def get_freq_group(code: int) -> FreqGroup: ...
+    def from_period_dtype_code(code: int) -> FreqGroup: ...
 
 class Resolution(Enum):
     RESO_NS: int
@@ -49,10 +49,10 @@ class Resolution(Enum):
     def __lt__(self, other: Resolution) -> bool: ...
     def __ge__(self, other: Resolution) -> bool: ...
     @property
-    def freq_group(self) -> FreqGroup: ...
-    @property
     def attrname(self) -> str: ...
     @classmethod
     def from_attrname(cls, attrname: str) -> Resolution: ...
     @classmethod
-    def get_reso_from_freq(cls, freq: str) -> Resolution: ...
+    def get_reso_from_freqstr(cls, freq: str) -> Resolution: ...
+    @property
+    def attr_abbrev(self) -> str: ...