API: to_timedelta(integers, unit) give requested unit

Author: jbrockmendel

pandas/_libs/tslibs/timedeltas.pyx

@@ -44,6 +44,7 @@ from pandas._libs.tslibs.conversion cimport (
     cast_from_unit,
 )
 from pandas._libs.tslibs.dtypes cimport (
+    abbrev_to_npy_unit,
     c_DEPR_UNITS,
     get_supported_reso,
     is_supported_unit,
@@ -359,11 +360,16 @@ def array_to_timedelta64(
         cnp.broadcast mi = cnp.PyArray_MultiIterNew2(result, values)
         cnp.flatiter it
         str parsed_unit = parse_timedelta_unit(unit or "ns")
-        NPY_DATETIMEUNIT item_reso
+        NPY_DATETIMEUNIT item_reso, int_reso
         ResoState state = ResoState(creso)
         bint infer_reso = creso == NPY_DATETIMEUNIT.NPY_FR_GENERIC
         ndarray iresult = result.view("i8")
 
+    if unit is None:
+        int_reso = NPY_FR_ns
+    else:
+        int_reso = get_supported_reso(abbrev_to_npy_unit(parsed_unit))
+
     if values.descr.type_num != cnp.NPY_OBJECT:
         # raise here otherwise we segfault below
         raise TypeError("array_to_timedelta64 'values' must have object dtype")
@@ -472,7 +478,18 @@ def array_to_timedelta64(
                     creso = state.creso
                 ival = delta_to_nanoseconds(item, reso=creso)
 
-            elif is_integer_object(item) or is_float_object(item):
+            elif is_integer_object(item):
+                if item == NPY_NAT:
+                    ival = NPY_NAT
+                else:
+                    ival = _numeric_to_td64ns(item, parsed_unit, int_reso)
+                    item_reso = int_reso
+
+                    state.update_creso(item_reso)
+                    if infer_reso:
+                        creso = state.creso
+
+            elif is_float_object(item):
                 ival = _numeric_to_td64ns(item, parsed_unit, NPY_FR_ns)
 
                 item_reso = NPY_FR_ns

pandas/tests/arithmetic/test_timedelta64.py

@@ -729,11 +729,12 @@ def test_tdi_add_overflow(self):
         # TODO: Make raised error message more informative and test
 
         _NaT = NaT._value + 1
+        td = pd.to_timedelta([106580], "D").as_unit("ns")
         msg = "Overflow in int64 addition"
         with pytest.raises(OverflowError, match=msg):
-            pd.to_timedelta([106580], "D") + Timestamp("2000")
+            td + Timestamp("2000")
         with pytest.raises(OverflowError, match=msg):
-            Timestamp("2000") + pd.to_timedelta([106580], "D")
+            Timestamp("2000") + td
         with pytest.raises(OverflowError, match=msg):
             pd.to_timedelta([_NaT]) - Timedelta("1 days")
         with pytest.raises(OverflowError, match=msg):

pandas/tests/indexes/timedeltas/methods/test_shift.py

@@ -49,7 +49,7 @@ def test_tdi_shift_int(self):
                 "5 days 01:00:00",
             ],
             freq="D",
-            dtype="m8[ns]",
+            dtype="m8[s]",
         )
         tm.assert_index_equal(result, expected)
 
@@ -67,7 +67,7 @@ def test_tdi_shift_nonstandard_freq(self):
                 "10 days 01:00:03",
             ],
             freq="D",
-            dtype="m8[ns]",
+            dtype="m8[s]",
         )
         tm.assert_index_equal(result, expected)
 

pandas/tests/indexes/timedeltas/test_constructors.py

@@ -267,4 +267,5 @@ def test_unit_deprecated(self, unit, unit_depr):
 
         with tm.assert_produces_warning(Pandas4Warning, match=msg):
             tdi = to_timedelta([1, 2], unit=unit_depr)
-        tm.assert_index_equal(tdi, expected.as_unit("ns"))
+        exp_unit = unit if unit in ["s", "ms", "us"] else "s"
+        tm.assert_index_equal(tdi, expected.as_unit(exp_unit))

pandas/tests/resample/test_timedelta.py

@@ -101,9 +101,7 @@ def test_resample_categorical_data_with_timedeltaindex():
     df = DataFrame({"Group_obj": "A"}, index=pd.to_timedelta(list(range(20)), unit="s"))
     df["Group"] = df["Group_obj"].astype("category")
     result = df.resample("10s").agg(lambda x: (x.value_counts().index[0]))
-    exp_tdi = pd.TimedeltaIndex(np.array([0, 10], dtype="m8[s]"), freq="10s").as_unit(
-        "ns"
-    )
+    exp_tdi = pd.TimedeltaIndex(np.array([0, 10], dtype="m8[s]"), freq="10s")
     expected = DataFrame(
         {"Group_obj": ["A", "A"], "Group": ["A", "A"]},
         index=exp_tdi,

pandas/tests/scalar/timedelta/test_constructors.py

@@ -155,11 +155,7 @@ def test_unit_deprecated(self, unit, unit_depr):
     def test_unit_parser(self, unit, np_unit, wrapper):
         # validate all units, GH 6855, GH 21762
         # array-likes
-        if wrapper is list:
-            # we go through _objects_to_td64ns which hasn't yet been updated
-            exp_unit = "ns"
-        else:
-            exp_unit = np_unit if np_unit not in ["W", "D", "m"] else "s"
+        exp_unit = np_unit if np_unit not in ["W", "D", "m"] else "s"
         expected = TimedeltaIndex(
             [np.timedelta64(i, np_unit) for i in np.arange(5).tolist()],
             dtype=f"m8[{exp_unit}]",

pandas/tests/tools/test_to_timedelta.py

@@ -104,7 +104,7 @@ def test_to_timedelta_units(self):
         result = TimedeltaIndex(
             [np.timedelta64(0, "ns"), np.timedelta64(10, "s").astype("m8[ns]")]
         )
-        expected = to_timedelta([0, 10], unit="s")
+        expected = to_timedelta([0, 10], unit="s").as_unit("ns")
         tm.assert_index_equal(result, expected)
 
     @pytest.mark.parametrize(