POC/ENH: Timedelta min/max/resolution support non-nano (pandas-dev#47641)

ENH: Timedelta min/max/resolution support non-nano

Author: jbrockmendel

pandas/_libs/tslibs/timedeltas.pyx

@@ -950,14 +950,18 @@ cdef _timedelta_from_value_and_reso(int64_t value, NPY_DATETIMEUNIT reso):
     cdef:
         _Timedelta td_base
 
+    # For millisecond and second resos, we cannot actually pass int(value) because
+    #  many cases would fall outside of the pytimedelta implementation bounds.
+    #  We pass 0 instead, and override seconds, microseconds, days.
+    #  In principle we could pass 0 for ns and us too.
     if reso == NPY_FR_ns:
         td_base = _Timedelta.__new__(Timedelta, microseconds=int(value) // 1000)
     elif reso == NPY_DATETIMEUNIT.NPY_FR_us:
         td_base = _Timedelta.__new__(Timedelta, microseconds=int(value))
     elif reso == NPY_DATETIMEUNIT.NPY_FR_ms:
-        td_base = _Timedelta.__new__(Timedelta, milliseconds=int(value))
+        td_base = _Timedelta.__new__(Timedelta, milliseconds=0)
     elif reso == NPY_DATETIMEUNIT.NPY_FR_s:
-        td_base = _Timedelta.__new__(Timedelta, seconds=int(value))
+        td_base = _Timedelta.__new__(Timedelta, seconds=0)
     # Other resolutions are disabled but could potentially be implemented here:
     # elif reso == NPY_DATETIMEUNIT.NPY_FR_m:
     #    td_base = _Timedelta.__new__(Timedelta, minutes=int(value))
@@ -977,6 +981,34 @@ cdef _timedelta_from_value_and_reso(int64_t value, NPY_DATETIMEUNIT reso):
     return td_base
 
 
+class MinMaxReso:
+    """
+    We need to define min/max/resolution on both the Timedelta _instance_
+    and Timedelta class.  On an instance, these depend on the object's _reso.
+    On the class, we default to the values we would get with nanosecond _reso.
+    """
+    def __init__(self, name):
+        self._name = name
+
+    def __get__(self, obj, type=None):
+        if self._name == "min":
+            val = np.iinfo(np.int64).min + 1
+        elif self._name == "max":
+            val = np.iinfo(np.int64).max
+        else:
+            assert self._name == "resolution"
+            val = 1
+
+        if obj is None:
+            # i.e. this is on the class, default to nanos
+            return Timedelta(val)
+        else:
+            return Timedelta._from_value_and_reso(val, obj._reso)
+
+    def __set__(self, obj, value):
+        raise AttributeError(f"{self._name} is not settable.")
+
+
 # Similar to Timestamp/datetime, this is a construction requirement for
 # timedeltas that we need to do object instantiation in python. This will
 # serve as a C extension type that shadows the Python class, where we do any
@@ -990,6 +1022,36 @@ cdef class _Timedelta(timedelta):
 
     # higher than np.ndarray and np.matrix
     __array_priority__ = 100
+    min = MinMaxReso("min")
+    max = MinMaxReso("max")
+    resolution = MinMaxReso("resolution")
+
+    @property
+    def days(self) -> int:  # TODO(cython3): make cdef property
+        # NB: using the python C-API PyDateTime_DELTA_GET_DAYS will fail
+        #  (or be incorrect)
+        self._ensure_components()
+        return self._d
+
+    @property
+    def seconds(self) -> int:  # TODO(cython3): make cdef property
+        # NB: using the python C-API PyDateTime_DELTA_GET_SECONDS will fail
+        #  (or be incorrect)
+        self._ensure_components()
+        return self._h * 3600 + self._m * 60 + self._s
+
+    @property
+    def microseconds(self) -> int:  # TODO(cython3): make cdef property
+        # NB: using the python C-API PyDateTime_DELTA_GET_MICROSECONDS will fail
+        #  (or be incorrect)
+        self._ensure_components()
+        return self._ms * 1000 + self._us
+
+    def total_seconds(self) -> float:
+        """Total seconds in the duration."""
+        # We need to override bc we overrided days/seconds/microseconds
+        # TODO: add nanos/1e9?
+        return self.days * 24 * 3600 + self.seconds + self.microseconds / 1_000_000
 
     @property
     def freq(self) -> None:
@@ -1979,9 +2041,3 @@ cdef _broadcast_floordiv_td64(
         res = res.astype('f8')
         res[mask] = np.nan
     return res
-
-
-# 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/tests/scalar/timedelta/test_timedelta.py

@@ -101,18 +101,23 @@ def test_as_unit_non_nano(self):
 
 
 class TestNonNano:
-    @pytest.fixture(params=[7, 8, 9])
-    def unit(self, request):
-        # 7, 8, 9 correspond to second, millisecond, and microsecond, respectively
+    @pytest.fixture(params=["s", "ms", "us"])
+    def unit_str(self, request):
         return request.param
 
+    @pytest.fixture
+    def unit(self, unit_str):
+        # 7, 8, 9 correspond to second, millisecond, and microsecond, respectively
+        attr = f"NPY_FR_{unit_str}"
+        return getattr(NpyDatetimeUnit, attr).value
+
     @pytest.fixture
     def val(self, unit):
         # microsecond that would be just out of bounds for nano
         us = 9223372800000000
-        if unit == 9:
+        if unit == NpyDatetimeUnit.NPY_FR_us.value:
             value = us
-        elif unit == 8:
+        elif unit == NpyDatetimeUnit.NPY_FR_ms.value:
             value = us // 1000
         else:
             value = us // 1_000_000
@@ -166,11 +171,11 @@ def test_to_timedelta64(self, td, unit):
 
             assert isinstance(res, np.timedelta64)
             assert res.view("i8") == td.value
-            if unit == 7:
+            if unit == NpyDatetimeUnit.NPY_FR_s.value:
                 assert res.dtype == "m8[s]"
-            elif unit == 8:
+            elif unit == NpyDatetimeUnit.NPY_FR_ms.value:
                 assert res.dtype == "m8[ms]"
-            elif unit == 9:
+            elif unit == NpyDatetimeUnit.NPY_FR_us.value:
                 assert res.dtype == "m8[us]"
 
     def test_truediv_timedeltalike(self, td):
@@ -266,6 +271,35 @@ def test_addsub_mismatched_reso(self, td):
         with pytest.raises(ValueError, match=msg):
             other2 - td
 
+    def test_min(self, td):
+        assert td.min <= td
+        assert td.min._reso == td._reso
+        assert td.min.value == NaT.value + 1
+
+    def test_max(self, td):
+        assert td.max >= td
+        assert td.max._reso == td._reso
+        assert td.max.value == np.iinfo(np.int64).max
+
+    def test_resolution(self, td):
+        expected = Timedelta._from_value_and_reso(1, td._reso)
+        result = td.resolution
+        assert result == expected
+        assert result._reso == expected._reso
+
+
+def test_timedelta_class_min_max_resolution():
+    # when accessed on the class (as opposed to an instance), we default
+    #  to nanoseconds
+    assert Timedelta.min == Timedelta(NaT.value + 1)
+    assert Timedelta.min._reso == NpyDatetimeUnit.NPY_FR_ns.value
+
+    assert Timedelta.max == Timedelta(np.iinfo(np.int64).max)
+    assert Timedelta.max._reso == NpyDatetimeUnit.NPY_FR_ns.value
+
+    assert Timedelta.resolution == Timedelta(1)
+    assert Timedelta.resolution._reso == NpyDatetimeUnit.NPY_FR_ns.value
+
 
 class TestTimedeltaUnaryOps:
     def test_invert(self):