BUG: Adds missing raises for numpy.timedelta64[M/Y] in pandas.Timedelta

doc/source/user_guide/timedeltas.rst

@@ -259,9 +259,6 @@ an alternative is to divide by another timedelta object. Note that division by t
    # to days
    td / np.timedelta64(1, "D")
 
-   # to months (these are constant months)
-   td / np.timedelta64(1, "M")
-
 Dividing or multiplying a ``timedelta64[ns]`` Series by an integer or integer Series
 yields another ``timedelta64[ns]`` dtypes Series.
 

doc/source/whatsnew/v2.1.0.rst

@@ -365,6 +365,7 @@ Timedelta
 ^^^^^^^^^
 - :meth:`TimedeltaIndex.map` with ``na_action="ignore"`` now works as expected (:issue:`51644`)
 - Bug in :class:`TimedeltaIndex` division or multiplication leading to ``.freq`` of "0 Days" instead of ``None`` (:issue:`51575`)
+- Bug in :class:`Timedelta` with Numpy timedelta64 objects not properly raising ``ValueError`` (:issue:`52806`)
 - Bug in :meth:`Timedelta.round` with values close to the implementation bounds returning incorrect results instead of raising ``OutOfBoundsTimedelta`` (:issue:`51494`)
 - Bug in :meth:`arrays.TimedeltaArray.map` and :meth:`TimedeltaIndex.map`, where the supplied callable operated array-wise instead of element-wise (:issue:`51977`)
 -

pandas/_libs/tslibs/dtypes.pxd

@@ -9,6 +9,7 @@ cdef NPY_DATETIMEUNIT freq_group_code_to_npy_unit(int freq) noexcept nogil
 cpdef int64_t periods_per_day(NPY_DATETIMEUNIT reso=*) except? -1
 cpdef int64_t periods_per_second(NPY_DATETIMEUNIT reso) except? -1
 cpdef NPY_DATETIMEUNIT get_supported_reso(NPY_DATETIMEUNIT reso)
+cpdef bint is_supported_unit(NPY_DATETIMEUNIT reso)
 
 cdef dict attrname_to_abbrevs
 cdef dict npy_unit_to_attrname

pandas/_libs/tslibs/dtypes.pyx

@@ -321,7 +321,7 @@ cpdef NPY_DATETIMEUNIT get_supported_reso(NPY_DATETIMEUNIT reso):
     return reso
 
 
-def is_supported_unit(NPY_DATETIMEUNIT reso):
+cpdef bint is_supported_unit(NPY_DATETIMEUNIT reso):
     return (
         reso == NPY_DATETIMEUNIT.NPY_FR_ns
         or reso == NPY_DATETIMEUNIT.NPY_FR_us

pandas/_libs/tslibs/timedeltas.pyx

@@ -42,6 +42,7 @@ from pandas._libs.tslibs.conversion cimport (
 )
 from pandas._libs.tslibs.dtypes cimport (
     get_supported_reso,
+    is_supported_unit,
     npy_unit_to_abbrev,
 )
 from pandas._libs.tslibs.nattype cimport (
@@ -151,10 +152,10 @@ cdef dict timedelta_abbrevs = {
 
 _no_input = object()
 
-
 # ----------------------------------------------------------------------
 # API
 
+
 @cython.boundscheck(False)
 @cython.wraparound(False)
 def ints_to_pytimedelta(ndarray m8values, box=False):
@@ -1789,7 +1790,6 @@ class Timedelta(_Timedelta):
                 + int(kwargs.get("milliseconds", 0) * 1_000_000)
                 + seconds
             )
-
         if unit in {"Y", "y", "M"}:
             raise ValueError(
                 "Units 'M', 'Y', and 'y' are no longer supported, as they do not "
@@ -1836,6 +1836,15 @@ class Timedelta(_Timedelta):
                 return NaT
 
             reso = get_datetime64_unit(value)
+            if not (is_supported_unit(reso) or
+                    reso in [NPY_DATETIMEUNIT.NPY_FR_m,
+                             NPY_DATETIMEUNIT.NPY_FR_h,
+                             NPY_DATETIMEUNIT.NPY_FR_D,
+                             NPY_DATETIMEUNIT.NPY_FR_W,
+                             NPY_DATETIMEUNIT.NPY_FR_GENERIC]):
+                err = npy_unit_to_abbrev(reso)
+                raise ValueError(f" cannot construct a Timedelta from a unit {err}")
+
             new_reso = get_supported_reso(reso)
             if reso != NPY_DATETIMEUNIT.NPY_FR_GENERIC:
                 try:

pandas/tests/libs/test_lib.py

@@ -59,7 +59,7 @@ def test_fast_multiget_timedelta_resos(self):
         tm.assert_numpy_array_equal(result, expected)
 
         # case that can't be cast to td64ns
-        td = Timedelta(np.timedelta64(400, "Y"))
+        td = Timedelta(np.timedelta64(146000, "D"))
         assert hash(td) == hash(td.as_unit("ms"))
         assert hash(td) == hash(td.as_unit("us"))
         mapping1 = {td: 1}

pandas/tests/scalar/timedelta/test_constructors.py

@@ -289,7 +289,6 @@ def test_overflow_on_construction():
 @pytest.mark.parametrize(
     "val, unit",
     [
-        (3508, "M"),
         (15251, "W"),  # 1
         (106752, "D"),  # change from previous:
         (2562048, "h"),  # 0 hours
@@ -333,7 +332,6 @@ def test_construction_out_of_bounds_td64ns(val, unit):
 @pytest.mark.parametrize(
     "val, unit",
     [
-        (3508 * 10**9, "M"),
         (15251 * 10**9, "W"),
         (106752 * 10**9, "D"),
         (2562048 * 10**9, "h"),

pandas/tests/tslibs/test_timedeltas.py

@@ -72,6 +72,15 @@ def test_delta_to_nanoseconds_td64_MY_raises():
         delta_to_nanoseconds(td)
 
 
+@pytest.mark.parametrize("unit", ["Y", "M"])
+def test_unsupported_td64_unit_raises(unit):
+    # GH 52806
+    with pytest.raises(
+        ValueError, match=f"cannot construct a Timedelta from a unit {unit}"
+    ):
+        Timedelta(np.timedelta64(1, unit))
+
+
 def test_huge_nanoseconds_overflow():
     # GH 32402
     assert delta_to_nanoseconds(Timedelta(1e10)) == 1e10