ENH: ints_to_pytimedelta support non-nano (pandas-dev#46828)

Author: jbrockmendel

pandas/_libs/tslibs/timedeltas.pyi

@@ -63,7 +63,7 @@ UnitChoices = Literal[
 _S = TypeVar("_S", bound=timedelta)
 
 def ints_to_pytimedelta(
-    arr: npt.NDArray[np.int64],  # const int64_t[:]
+    arr: npt.NDArray[np.timedelta64],
     box: bool = ...,
 ) -> npt.NDArray[np.object_]: ...
 def array_to_timedelta64(

pandas/_libs/tslibs/timedeltas.pyx

@@ -49,6 +49,7 @@ from pandas._libs.tslibs.np_datetime cimport (
     cmp_scalar,
     get_datetime64_unit,
     get_timedelta64_value,
+    get_unit_from_dtype,
     npy_datetimestruct,
     pandas_datetime_to_datetimestruct,
     pandas_timedelta_to_timedeltastruct,
@@ -141,14 +142,14 @@ _no_input = object()
 
 @cython.boundscheck(False)
 @cython.wraparound(False)
-def ints_to_pytimedelta(const int64_t[:] arr, box=False):
+def ints_to_pytimedelta(ndarray m8values, box=False):
     """
     convert an i8 repr to an ndarray of timedelta or Timedelta (if box ==
     True)
 
     Parameters
     ----------
-    arr : ndarray[int64_t]
+    arr : ndarray[timedelta64]
     box : bool, default False
 
     Returns
@@ -157,9 +158,12 @@ def ints_to_pytimedelta(const int64_t[:] arr, box=False):
         array of Timedelta or timedeltas objects
     """
     cdef:
-        Py_ssize_t i, n = len(arr)
+        Py_ssize_t i, n = m8values.size
         int64_t value
         object[::1] result = np.empty(n, dtype=object)
+        NPY_DATETIMEUNIT reso = get_unit_from_dtype(m8values.dtype)
+
+    arr = m8values.view("i8")
 
     for i in range(n):
 
@@ -168,9 +172,26 @@ def ints_to_pytimedelta(const int64_t[:] arr, box=False):
             result[i] = <object>NaT
         else:
             if box:
-                result[i] = Timedelta(value)
-            else:
+                result[i] = _timedelta_from_value_and_reso(value, reso=reso)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_ns:
                 result[i] = timedelta(microseconds=int(value) / 1000)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_us:
+                result[i] = timedelta(microseconds=value)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_ms:
+                result[i] = timedelta(milliseconds=value)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_s:
+                result[i] = timedelta(seconds=value)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_m:
+                result[i] = timedelta(minutes=value)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_h:
+                result[i] = timedelta(hours=value)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_D:
+                result[i] = timedelta(days=value)
+            elif reso == NPY_DATETIMEUNIT.NPY_FR_W:
+                result[i] = timedelta(weeks=value)
+            else:
+                # Month, Year, NPY_FR_GENERIC, pico, fempto, atto
+                raise NotImplementedError(reso)
 
     return result.base  # .base to access underlying np.ndarray
 
@@ -1530,6 +1551,9 @@ class Timedelta(_Timedelta):
             int64_t result, unit, remainder
             ndarray[int64_t] arr
 
+        if self._reso != NPY_FR_ns:
+            raise NotImplementedError
+
         from pandas._libs.tslibs.offsets import to_offset
         unit = to_offset(freq).nanos
 
@@ -1620,6 +1644,8 @@ class Timedelta(_Timedelta):
 
         elif is_integer_object(other) or is_float_object(other):
             # integers or floats
+            if self._reso != NPY_FR_ns:
+                raise NotImplementedError
             return Timedelta(self.value / other, unit='ns')
 
         elif is_array(other):
@@ -1633,6 +1659,8 @@ class Timedelta(_Timedelta):
             other = Timedelta(other)
             if other is NaT:
                 return np.nan
+            if self._reso != NPY_FR_ns:
+                raise NotImplementedError
             return float(other.value) / self.value
 
         elif is_array(other):
@@ -1651,17 +1679,25 @@ class Timedelta(_Timedelta):
             other = Timedelta(other)
             if other is NaT:
                 return np.nan
+            if self._reso != NPY_FR_ns:
+                raise NotImplementedError
             return self.value // other.value
 
         elif is_integer_object(other) or is_float_object(other):
+            if self._reso != NPY_FR_ns:
+                raise NotImplementedError
             return Timedelta(self.value // other, unit='ns')
 
         elif is_array(other):
             if other.dtype.kind == 'm':
                 # also timedelta-like
+                if self._reso != NPY_FR_ns:
+                    raise NotImplementedError
                 return _broadcast_floordiv_td64(self.value, other, _floordiv)
             elif other.dtype.kind in ['i', 'u', 'f']:
                 if other.ndim == 0:
+                    if self._reso != NPY_FR_ns:
+                        raise NotImplementedError
                     return Timedelta(self.value // other)
                 else:
                     return self.to_timedelta64() // other
@@ -1678,11 +1714,15 @@ class Timedelta(_Timedelta):
             other = Timedelta(other)
             if other is NaT:
                 return np.nan
+            if self._reso != NPY_FR_ns:
+                raise NotImplementedError
             return other.value // self.value
 
         elif is_array(other):
             if other.dtype.kind == 'm':
                 # also timedelta-like
+                if self._reso != NPY_FR_ns:
+                    raise NotImplementedError
                 return _broadcast_floordiv_td64(self.value, other, _rfloordiv)
 
             # Includes integer array // Timedelta, disallowed in GH#19761

pandas/core/arrays/datetimelike.py

@@ -432,7 +432,7 @@ def astype(self, dtype, copy: bool = True):
 
             elif self.dtype.kind == "m":
                 i8data = self.asi8.ravel()
-                converted = ints_to_pytimedelta(i8data, box=True)
+                converted = ints_to_pytimedelta(self._ndarray.ravel(), box=True)
                 return converted.reshape(self.shape)
 
             return self._box_values(self.asi8.ravel()).reshape(self.shape)

pandas/core/arrays/timedeltas.py

@@ -369,7 +369,7 @@ def __iter__(self):
                 yield self[i]
         else:
             # convert in chunks of 10k for efficiency
-            data = self.asi8
+            data = self._ndarray
             length = len(self)
             chunksize = 10000
             chunks = (length // chunksize) + 1
@@ -886,7 +886,7 @@ def to_pytimedelta(self) -> np.ndarray:
         -------
         timedeltas : ndarray[object]
         """
-        return tslibs.ints_to_pytimedelta(self.asi8)
+        return tslibs.ints_to_pytimedelta(self._ndarray)
 
     days = _field_accessor("days", "days", "Number of days for each element.")
     seconds = _field_accessor(

pandas/tests/tslibs/test_timedeltas.py

@@ -6,12 +6,14 @@
 from pandas._libs.tslibs.timedeltas import (
     array_to_timedelta64,
     delta_to_nanoseconds,
+    ints_to_pytimedelta,
 )
 
 from pandas import (
     Timedelta,
     offsets,
 )
+import pandas._testing as tm
 
 
 @pytest.mark.parametrize(
@@ -89,3 +91,29 @@ def test_array_to_timedelta64_non_object_raises(self):
         msg = "'values' must have object dtype"
         with pytest.raises(TypeError, match=msg):
             array_to_timedelta64(values)
+
+
+@pytest.mark.parametrize("unit", ["s", "ms", "us"])
+def test_ints_to_pytimedelta(unit):
+    # tests for non-nanosecond cases
+    arr = np.arange(6, dtype=np.int64).view(f"m8[{unit}]")
+
+    res = ints_to_pytimedelta(arr, box=False)
+    # For non-nanosecond, .astype(object) gives pytimedelta objects
+    #  instead of integers
+    expected = arr.astype(object)
+    tm.assert_numpy_array_equal(res, expected)
+
+    res = ints_to_pytimedelta(arr, box=True)
+    expected = np.array([Timedelta(x) for x in arr], dtype=object)
+    tm.assert_numpy_array_equal(res, expected)
+
+
+@pytest.mark.parametrize("unit", ["Y", "M", "ps", "fs", "as"])
+def test_ints_to_pytimedelta_unsupported(unit):
+    arr = np.arange(6, dtype=np.int64).view(f"m8[{unit}]")
+
+    with pytest.raises(NotImplementedError, match=r"\d{1,2}"):
+        ints_to_pytimedelta(arr, box=False)
+    with pytest.raises(NotImplementedError, match=r"\d{1,2}"):
+        ints_to_pytimedelta(arr, box=True)