BUG/DEPR: Timestamp/Timedelta resolution (pandas-dev#29910)

* BUG/DEPR: Timestamp/Timedelta resolution

* GH ref

Author: jbrockmendel

doc/source/whatsnew/v1.0.0.rst

@@ -457,6 +457,7 @@ or ``matplotlib.Axes.plot``. See :ref:`plotting.formatters` for more.
 - Removed previously deprecated keyword "n" from :meth:`DatetimeIndex.shift`, :meth:`TimedeltaIndex.shift`, :meth:`PeriodIndex.shift`, use "periods" instead (:issue:`22458`)
 - Changed the default value for the `raw` argument in :func:`Series.rolling().apply() <pandas.core.window.Rolling.apply>`, :func:`DataFrame.rolling().apply() <pandas.core.window.Rolling.apply>`,
 - :func:`Series.expanding().apply() <pandas.core.window.Expanding.apply>`, and :func:`DataFrame.expanding().apply() <pandas.core.window.Expanding.apply>` to ``False`` (:issue:`20584`)
+- Changed :meth:`Timedelta.resolution` to match the behavior of the standard library ``datetime.timedelta.resolution``, for the old behavior, use :meth:`Timedelta.resolution_string` (:issue:`26839`)
 - Removed previously deprecated :attr:`Timestamp.weekday_name`, :attr:`DatetimeIndex.weekday_name`, and :attr:`Series.dt.weekday_name` (:issue:`18164`)
 - Removed previously deprecated ``errors`` argument in :meth:`Timestamp.tz_localize`, :meth:`DatetimeIndex.tz_localize`, and :meth:`Series.tz_localize` (:issue:`22644`)
 -
@@ -516,6 +517,7 @@ Datetimelike
 - Bug in :func:`pandas._config.localization.get_locales` where the ``locales -a`` encodes the locales list as windows-1252 (:issue:`23638`, :issue:`24760`, :issue:`27368`)
 - Bug in :meth:`Series.var` failing to raise ``TypeError`` when called with ``timedelta64[ns]`` dtype (:issue:`28289`)
 - Bug in :meth:`DatetimeIndex.strftime` and :meth:`Series.dt.strftime` where ``NaT`` was converted to the string ``'NaT'`` instead of ``np.nan`` (:issue:`29578`)
+- Bug in :attr:`Timestamp.resolution` being a property instead of a class attribute (:issue:`29910`)
 
 Timedelta
 ^^^^^^^^^

pandas/_libs/tslibs/timedeltas.pyx

@@ -1005,56 +1005,6 @@ cdef class _Timedelta(timedelta):
         else:
             return "D"
 
-    @property
-    def resolution(self):
-        """
-        Return a string representing the lowest timedelta resolution.
-
-        Each timedelta has a defined resolution that represents the lowest OR
-        most granular level of precision. Each level of resolution is
-        represented by a short string as defined below:
-
-        Resolution:     Return value
-
-        * Days:         'D'
-        * Hours:        'H'
-        * Minutes:      'T'
-        * Seconds:      'S'
-        * Milliseconds: 'L'
-        * Microseconds: 'U'
-        * Nanoseconds:  'N'
-
-        Returns
-        -------
-        str
-            Timedelta resolution.
-
-        Examples
-        --------
-        >>> td = pd.Timedelta('1 days 2 min 3 us 42 ns')
-        >>> td.resolution
-        'N'
-
-        >>> td = pd.Timedelta('1 days 2 min 3 us')
-        >>> td.resolution
-        'U'
-
-        >>> td = pd.Timedelta('2 min 3 s')
-        >>> td.resolution
-        'S'
-
-        >>> td = pd.Timedelta(36, unit='us')
-        >>> td.resolution
-        'U'
-        """
-        # See GH#21344
-        warnings.warn("Timedelta.resolution is deprecated, in a future "
-                      "version will behave like the standard library "
-                      "datetime.timedelta.resolution attribute.  "
-                      "Use Timedelta.resolution_string instead.",
-                      FutureWarning)
-        return self.resolution_string
-
     @property
     def nanoseconds(self):
         """
@@ -1602,3 +1552,4 @@ cdef _broadcast_floordiv_td64(int64_t value, object other,
 # resolution in ns
 Timedelta.min = Timedelta(np.iinfo(np.int64).min + 1)
 Timedelta.max = Timedelta(np.iinfo(np.int64).max)
+Timedelta.resolution = Timedelta(nanoseconds=1)

pandas/_libs/tslibs/timestamps.pyx

@@ -744,15 +744,6 @@ timedelta}, default 'raise'
         """
         return bool(ccalendar.is_leapyear(self.year))
 
-    @property
-    def resolution(self):
-        """
-        Return resolution describing the smallest difference between two
-        times that can be represented by Timestamp object_state.
-        """
-        # GH#21336, GH#21365
-        return Timedelta(nanoseconds=1)
-
     def tz_localize(self, tz, ambiguous='raise', nonexistent='raise'):
         """
         Convert naive Timestamp to local time zone, or remove
@@ -1036,3 +1027,4 @@ cdef int64_t _NS_LOWER_BOUND = -9223372036854775000
 # Resolution is in nanoseconds
 Timestamp.min = Timestamp(_NS_LOWER_BOUND)
 Timestamp.max = Timestamp(_NS_UPPER_BOUND)
+Timestamp.resolution = Timedelta(nanoseconds=1)  # GH#21336, GH#21365

pandas/tests/scalar/timedelta/test_timedelta.py

@@ -804,9 +804,13 @@ def test_resolution_string(self):
     def test_resolution_deprecated(self):
         # GH#21344
         td = Timedelta(days=4, hours=3)
-        with tm.assert_produces_warning(FutureWarning) as w:
-            td.resolution
-        assert "Use Timedelta.resolution_string instead" in str(w[0].message)
+        result = td.resolution
+        assert result == Timedelta(nanoseconds=1)
+
+        # Check that the attribute is available on the class, mirroring
+        #  the stdlib timedelta behavior
+        result = Timedelta.resolution
+        assert result == Timedelta(nanoseconds=1)
 
 
 @pytest.mark.parametrize(

pandas/tests/scalar/timestamp/test_timestamp.py

@@ -192,6 +192,10 @@ def test_resolution(self):
         dt = Timestamp("2100-01-01 00:00:00")
         assert dt.resolution == Timedelta(nanoseconds=1)
 
+        # Check that the attribute is available on the class, mirroring
+        #  the stdlib datetime behavior
+        assert Timestamp.resolution == Timedelta(nanoseconds=1)
+
 
 class TestTimestampConstructors:
     def test_constructor(self):