Consistent handling of 0-dim in Timedelta arithmetic methods (#47390)

* Consistent handling of 0-dim in Timedelta arithmetic methods

* update test

Author: jbrockmendel

pandas/_libs/tslibs/timedeltas.pyx

@@ -765,8 +765,12 @@ def _binary_op_method_timedeltalike(op, name):
             # defined by Timestamp methods.
 
         elif is_array(other):
-            # nd-array like
-            if other.dtype.kind in ['m', 'M']:
+            if other.ndim == 0:
+                # see also: item_from_zerodim
+                item = cnp.PyArray_ToScalar(cnp.PyArray_DATA(other), other)
+                return f(self, item)
+
+            elif other.dtype.kind in ['m', 'M']:
                 return op(self.to_timedelta64(), other)
             elif other.dtype.kind == 'O':
                 return np.array([op(self, x) for x in other])
@@ -943,14 +947,18 @@ cdef _timedelta_from_value_and_reso(int64_t value, NPY_DATETIMEUNIT reso):
         td_base = _Timedelta.__new__(Timedelta, milliseconds=int(value))
     elif reso == NPY_DATETIMEUNIT.NPY_FR_s:
         td_base = _Timedelta.__new__(Timedelta, seconds=int(value))
-    elif reso == NPY_DATETIMEUNIT.NPY_FR_m:
-        td_base = _Timedelta.__new__(Timedelta, minutes=int(value))
-    elif reso == NPY_DATETIMEUNIT.NPY_FR_h:
-        td_base = _Timedelta.__new__(Timedelta, hours=int(value))
-    elif reso == NPY_DATETIMEUNIT.NPY_FR_D:
-        td_base = _Timedelta.__new__(Timedelta, days=int(value))
+    # 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))
+    # elif reso == NPY_DATETIMEUNIT.NPY_FR_h:
+    #    td_base = _Timedelta.__new__(Timedelta, hours=int(value))
+    # elif reso == NPY_DATETIMEUNIT.NPY_FR_D:
+    #    td_base = _Timedelta.__new__(Timedelta, days=int(value))
     else:
-        raise NotImplementedError(reso)
+        raise NotImplementedError(
+            "Only resolutions 's', 'ms', 'us', 'ns' are supported."
+        )
+
 
     td_base.value = value
     td_base._is_populated = 0
@@ -1006,7 +1014,6 @@ cdef class _Timedelta(timedelta):
     def __richcmp__(_Timedelta self, object other, int op):
         cdef:
             _Timedelta ots
-            int ndim
 
         if isinstance(other, _Timedelta):
             ots = other
@@ -1018,7 +1025,6 @@ cdef class _Timedelta(timedelta):
             return op == Py_NE
 
         elif util.is_array(other):
-            # TODO: watch out for zero-dim
             if other.dtype.kind == "m":
                 return PyObject_RichCompare(self.asm8, other, op)
             elif other.dtype.kind == "O":
@@ -1728,14 +1734,20 @@ class Timedelta(_Timedelta):
             )
 
         elif is_array(other):
-            # ndarray-like
+            if other.ndim == 0:
+                # see also: item_from_zerodim
+                item = cnp.PyArray_ToScalar(cnp.PyArray_DATA(other), other)
+                return self.__mul__(item)
             return other * self.to_timedelta64()
 
         return NotImplemented
 
     __rmul__ = __mul__
 
     def __truediv__(self, other):
+        cdef:
+            int64_t new_value
+
         if _should_cast_to_timedelta(other):
             # We interpret NaT as timedelta64("NaT")
             other = Timedelta(other)
@@ -1758,6 +1770,10 @@ class Timedelta(_Timedelta):
             )
 
         elif is_array(other):
+            if other.ndim == 0:
+                # see also: item_from_zerodim
+                item = cnp.PyArray_ToScalar(cnp.PyArray_DATA(other), other)
+                return self.__truediv__(item)
             return self.to_timedelta64() / other
 
         return NotImplemented
@@ -1777,9 +1793,17 @@ class Timedelta(_Timedelta):
             return float(other.value) / self.value
 
         elif is_array(other):
-            if other.dtype.kind == "O":
+            if other.ndim == 0:
+                # see also: item_from_zerodim
+                item = cnp.PyArray_ToScalar(cnp.PyArray_DATA(other), other)
+                return self.__rtruediv__(item)
+            elif other.dtype.kind == "O":
                 # GH#31869
                 return np.array([x / self for x in other])
+
+            # TODO: if other.dtype.kind == "m" and other.dtype != self.asm8.dtype
+            #  then should disallow for consistency with scalar behavior; requires
+            #  deprecation cycle. (or changing scalar behavior)
             return other / self.to_timedelta64()
 
         return NotImplemented
@@ -1806,6 +1830,11 @@ class Timedelta(_Timedelta):
             return type(self)._from_value_and_reso(self.value // other, self._reso)
 
         elif is_array(other):
+            if other.ndim == 0:
+                # see also: item_from_zerodim
+                item = cnp.PyArray_ToScalar(cnp.PyArray_DATA(other), other)
+                return self.__floordiv__(item)
+
             if other.dtype.kind == 'm':
                 # also timedelta-like
                 if self._reso != NPY_FR_ns:
@@ -1838,6 +1867,11 @@ class Timedelta(_Timedelta):
             return other.value // self.value
 
         elif is_array(other):
+            if other.ndim == 0:
+                # see also: item_from_zerodim
+                item = cnp.PyArray_ToScalar(cnp.PyArray_DATA(other), other)
+                return self.__rfloordiv__(item)
+
             if other.dtype.kind == 'm':
                 # also timedelta-like
                 if self._reso != NPY_FR_ns:
@@ -1923,23 +1957,17 @@ cdef _broadcast_floordiv_td64(
     result : varies based on `other`
     """
     # assumes other.dtype.kind == 'm', i.e. other is timedelta-like
+    # assumes other.ndim != 0
 
     # We need to watch out for np.timedelta64('NaT').
     mask = other.view('i8') == NPY_NAT
 
-    if other.ndim == 0:
-        if mask:
-            return np.nan
-
-        return operation(value, other.astype('m8[ns]', copy=False).astype('i8'))
-
-    else:
-        res = operation(value, other.astype('m8[ns]', copy=False).astype('i8'))
+    res = operation(value, other.astype('m8[ns]', copy=False).astype('i8'))
 
-        if mask.any():
-            res = res.astype('f8')
-            res[mask] = np.nan
-        return res
+    if mask.any():
+        res = res.astype('f8')
+        res[mask] = np.nan
+    return res
 
 
 # resolution in ns

pandas/_libs/tslibs/timestamps.pyx

@@ -215,6 +215,11 @@ cdef class _Timestamp(ABCTimestamp):
         if value == NPY_NAT:
             return NaT
 
+        if reso < NPY_DATETIMEUNIT.NPY_FR_s or reso > NPY_DATETIMEUNIT.NPY_FR_ns:
+            raise NotImplementedError(
+                "Only resolutions 's', 'ms', 'us', 'ns' are supported."
+            )
+
         obj.value = value
         pandas_datetime_to_datetimestruct(value, reso, &obj.dts)
         maybe_localize_tso(obj, tz, reso)

pandas/tests/indexes/timedeltas/test_indexing.py

@@ -14,6 +14,7 @@
     TimedeltaIndex,
     Timestamp,
     notna,
+    offsets,
     timedelta_range,
     to_timedelta,
 )
@@ -346,3 +347,14 @@ def test_contains_nonunique(self):
         ):
             idx = TimedeltaIndex(vals)
             assert idx[0] in idx
+
+    def test_contains(self):
+        # Checking for any NaT-like objects
+        # GH#13603
+        td = to_timedelta(range(5), unit="d") + offsets.Hour(1)
+        for v in [NaT, None, float("nan"), np.nan]:
+            assert not (v in td)
+
+        td = to_timedelta([NaT])
+        for v in [NaT, None, float("nan"), np.nan]:
+            assert v in td

pandas/tests/scalar/timedelta/test_arithmetic.py

@@ -318,6 +318,26 @@ def test_td_add_sub_dt64_ndarray(self):
         tm.assert_numpy_array_equal(-td + other, expected)
         tm.assert_numpy_array_equal(other - td, expected)
 
+    def test_td_add_sub_ndarray_0d(self):
+        td = Timedelta("1 day")
+        other = np.array(td.asm8)
+
+        result = td + other
+        assert isinstance(result, Timedelta)
+        assert result == 2 * td
+
+        result = other + td
+        assert isinstance(result, Timedelta)
+        assert result == 2 * td
+
+        result = other - td
+        assert isinstance(result, Timedelta)
+        assert result == 0 * td
+
+        result = td - other
+        assert isinstance(result, Timedelta)
+        assert result == 0 * td
+
 
 class TestTimedeltaMultiplicationDivision:
     """
@@ -395,6 +415,20 @@ def test_td_mul_numeric_ndarray(self):
         result = other * td
         tm.assert_numpy_array_equal(result, expected)
 
+    def test_td_mul_numeric_ndarray_0d(self):
+        td = Timedelta("1 day")
+        other = np.array(2)
+        assert other.ndim == 0
+        expected = Timedelta("2 days")
+
+        res = td * other
+        assert type(res) is Timedelta
+        assert res == expected
+
+        res = other * td
+        assert type(res) is Timedelta
+        assert res == expected
+
     def test_td_mul_td64_ndarray_invalid(self):
         td = Timedelta("1 day")
         other = np.array([Timedelta("2 Days").to_timedelta64()])
@@ -484,6 +518,14 @@ def test_td_div_td64_ndarray(self):
         result = other / td
         tm.assert_numpy_array_equal(result, expected * 4)
 
+    def test_td_div_ndarray_0d(self):
+        td = Timedelta("1 day")
+
+        other = np.array(1)
+        res = td / other
+        assert isinstance(res, Timedelta)
+        assert res == td
+
     # ---------------------------------------------------------------
     # Timedelta.__rdiv__
 
@@ -539,6 +581,13 @@ def test_td_rdiv_ndarray(self):
         with pytest.raises(TypeError, match=msg):
             arr / td
 
+    def test_td_rdiv_ndarray_0d(self):
+        td = Timedelta(10, unit="d")
+
+        arr = np.array(td.asm8)
+
+        assert arr / td == 1
+
     # ---------------------------------------------------------------
     # Timedelta.__floordiv__
 

pandas/tests/scalar/timedelta/test_timedelta.py

@@ -84,15 +84,15 @@ def test_as_unit_rounding(self):
 
     def test_as_unit_non_nano(self):
         # case where we are going neither to nor from nano
-        td = Timedelta(days=1)._as_unit("D")
+        td = Timedelta(days=1)._as_unit("ms")
         assert td.days == 1
-        assert td.value == 1
+        assert td.value == 86_400_000
         assert td.components.days == 1
         assert td._d == 1
         assert td.total_seconds() == 86400
 
-        res = td._as_unit("h")
-        assert res.value == 24
+        res = td._as_unit("us")
+        assert res.value == 86_400_000_000
         assert res.components.days == 1
         assert res.components.hours == 0
         assert res._d == 1
@@ -677,17 +677,6 @@ def test_round_non_nano(self, unit):
         assert res == Timedelta("1 days 02:35:00")
         assert res._reso == td._reso
 
-    def test_contains(self):
-        # Checking for any NaT-like objects
-        # GH 13603
-        td = to_timedelta(range(5), unit="d") + offsets.Hour(1)
-        for v in [NaT, None, float("nan"), np.nan]:
-            assert not (v in td)
-
-        td = to_timedelta([NaT])
-        for v in [NaT, None, float("nan"), np.nan]:
-            assert v in td
-
     def test_identity(self):
 
         td = Timedelta(10, unit="d")

pandas/tests/tslibs/test_timedeltas.py

@@ -127,5 +127,6 @@ def test_ints_to_pytimedelta_unsupported(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}"):
+    msg = "Only resolutions 's', 'ms', 'us', 'ns' are supported"
+    with pytest.raises(NotImplementedError, match=msg):
         ints_to_pytimedelta(arr, box=True)