BUG: pd.Timedelta(big_int, unit=W) silent overflow (#47268)

* BUG: pd.Timedelta(big_int, unit=W) silent overflow

* GH ref

* note exception changes in whatsnew

Author: jbrockmendel

doc/source/whatsnew/v1.5.0.rst

@@ -436,6 +436,7 @@ Other API changes
   The ``auth_local_webserver = False`` option is planned to stop working in
   October 2022. (:issue:`46312`)
 - :func:`read_json` now raises ``FileNotFoundError`` (previously ``ValueError``) when input is a string ending in ``.json``, ``.json.gz``, ``.json.bz2``, etc. but no such file exists. (:issue:`29102`)
+- Operations with :class:`Timestamp` or :class:`Timedelta` that would previously raise ``OverflowError`` instead raise ``OutOfBoundsDatetime`` or ``OutOfBoundsTimedelta`` where appropriate (:issue:`47268`)
 -
 
 .. ---------------------------------------------------------------------------
@@ -736,6 +737,7 @@ Timedelta
 ^^^^^^^^^
 - Bug in :func:`astype_nansafe` astype("timedelta64[ns]") fails when np.nan is included (:issue:`45798`)
 - Bug in constructing a :class:`Timedelta` with a ``np.timedelta64`` object and a ``unit`` sometimes silently overflowing and returning incorrect results instead of raising ``OutOfBoundsTimedelta`` (:issue:`46827`)
+- Bug in constructing a :class:`Timedelta` from a large integer or float with ``unit="W"`` silently overflowing and returning incorrect results instead of raising ``OutOfBoundsTimedelta`` (:issue:`47268`)
 -
 
 Time Zones

pandas/_libs/tslibs/timedeltas.pyx

@@ -316,6 +316,8 @@ cdef convert_to_timedelta64(object ts, str unit):
 
     Return an ns based int64
     """
+    # Caller is responsible for checking unit not in ["Y", "y", "M"]
+
     if checknull_with_nat(ts):
         return np.timedelta64(NPY_NAT, "ns")
     elif isinstance(ts, _Timedelta):
@@ -329,17 +331,9 @@ cdef convert_to_timedelta64(object ts, str unit):
         if ts == NPY_NAT:
             return np.timedelta64(NPY_NAT, "ns")
         else:
-            if unit in ["Y", "M", "W"]:
-                ts = np.timedelta64(ts, unit)
-            else:
-                ts = cast_from_unit(ts, unit)
-                ts = np.timedelta64(ts, "ns")
+            ts = _maybe_cast_from_unit(ts, unit)
     elif is_float_object(ts):
-        if unit in ["Y", "M", "W"]:
-            ts = np.timedelta64(int(ts), unit)
-        else:
-            ts = cast_from_unit(ts, unit)
-            ts = np.timedelta64(ts, "ns")
+        ts = _maybe_cast_from_unit(ts, unit)
     elif isinstance(ts, str):
         if (len(ts) > 0 and ts[0] == "P") or (len(ts) > 1 and ts[:2] == "-P"):
             ts = parse_iso_format_string(ts)
@@ -356,6 +350,20 @@ cdef convert_to_timedelta64(object ts, str unit):
     return ts.astype("timedelta64[ns]")
 
 
+cdef _maybe_cast_from_unit(ts, str unit):
+    # caller is responsible for checking
+    #  assert unit not in ["Y", "y", "M"]
+    try:
+        ts = cast_from_unit(ts, unit)
+    except OverflowError as err:
+        raise OutOfBoundsTimedelta(
+            f"Cannot cast {ts} from {unit} to 'ns' without overflow."
+        ) from err
+
+    ts = np.timedelta64(ts, "ns")
+    return ts
+
+
 @cython.boundscheck(False)
 @cython.wraparound(False)
 def array_to_timedelta64(
@@ -370,6 +378,8 @@ def array_to_timedelta64(
     -------
     np.ndarray[timedelta64ns]
     """
+    # Caller is responsible for checking
+    assert unit not in ["Y", "y", "M"]
 
     cdef:
         Py_ssize_t i, n = values.size
@@ -652,24 +662,20 @@ cdef inline timedelta_from_spec(object number, object frac, object unit):
     cdef:
         str n
 
-    try:
-        unit = ''.join(unit)
-
-        if unit in ["M", "Y", "y"]:
-            warnings.warn(
-                "Units 'M', 'Y' and 'y' do not represent unambiguous "
-                "timedelta values and will be removed in a future version.",
-                FutureWarning,
-                stacklevel=2,
-            )
+    unit = ''.join(unit)
+    if unit in ["M", "Y", "y"]:
+        warnings.warn(
+            "Units 'M', 'Y' and 'y' do not represent unambiguous "
+            "timedelta values and will be removed in a future version.",
+            FutureWarning,
+            stacklevel=3,
+        )
 
-        if unit == 'M':
-            # To parse ISO 8601 string, 'M' should be treated as minute,
-            # not month
-            unit = 'm'
-        unit = parse_timedelta_unit(unit)
-    except KeyError:
-        raise ValueError(f"invalid abbreviation: {unit}")
+    if unit == 'M':
+        # To parse ISO 8601 string, 'M' should be treated as minute,
+        # not month
+        unit = 'm'
+    unit = parse_timedelta_unit(unit)
 
     n = ''.join(number) + '.' + ''.join(frac)
     return cast_from_unit(float(n), unit)
@@ -696,7 +702,7 @@ cpdef inline str parse_timedelta_unit(str unit):
         return unit
     try:
         return timedelta_abbrevs[unit.lower()]
-    except (KeyError, AttributeError):
+    except KeyError:
         raise ValueError(f"invalid unit abbreviation: {unit}")
 
 # ----------------------------------------------------------------------

pandas/_libs/tslibs/timestamps.pyx

@@ -90,7 +90,10 @@ from pandas._libs.tslibs.np_datetime cimport (
     pydatetime_to_dt64,
 )
 
-from pandas._libs.tslibs.np_datetime import OutOfBoundsDatetime
+from pandas._libs.tslibs.np_datetime import (
+    OutOfBoundsDatetime,
+    OutOfBoundsTimedelta,
+)
 
 from pandas._libs.tslibs.offsets cimport (
     BaseOffset,
@@ -455,7 +458,7 @@ cdef class _Timestamp(ABCTimestamp):
             # Timedelta
             try:
                 return Timedelta(self.value - other.value)
-            except (OverflowError, OutOfBoundsDatetime) as err:
+            except (OverflowError, OutOfBoundsDatetime, OutOfBoundsTimedelta) as err:
                 if isinstance(other, _Timestamp):
                     if both_timestamps:
                         raise OutOfBoundsDatetime(

pandas/core/arrays/timedeltas.py

@@ -270,6 +270,8 @@ def _from_sequence_not_strict(
         if dtype:
             _validate_td64_dtype(dtype)
 
+        assert unit not in ["Y", "y", "M"]  # caller is responsible for checking
+
         explicit_none = freq is None
         freq = freq if freq is not lib.no_default else None
 
@@ -923,6 +925,8 @@ def sequence_to_td64ns(
     errors to be ignored; they are caught and subsequently ignored at a
     higher level.
     """
+    assert unit not in ["Y", "y", "M"]  # caller is responsible for checking
+
     inferred_freq = None
     if unit is not None:
         unit = parse_timedelta_unit(unit)
@@ -954,7 +958,7 @@ def sequence_to_td64ns(
     # Convert whatever we have into timedelta64[ns] dtype
     if is_object_dtype(data.dtype) or is_string_dtype(data.dtype):
         # no need to make a copy, need to convert if string-dtyped
-        data = objects_to_td64ns(data, unit=unit, errors=errors)
+        data = _objects_to_td64ns(data, unit=unit, errors=errors)
         copy = False
 
     elif is_integer_dtype(data.dtype):
@@ -1032,7 +1036,7 @@ def ints_to_td64ns(data, unit="ns"):
     return data, copy_made
 
 
-def objects_to_td64ns(data, unit=None, errors="raise"):
+def _objects_to_td64ns(data, unit=None, errors="raise"):
     """
     Convert a object-dtyped or string-dtyped array into an
     timedelta64[ns]-dtyped array.

pandas/tests/scalar/timedelta/test_arithmetic.py

@@ -99,8 +99,8 @@ def test_td_add_datetimelike_scalar(self, op):
         assert result is NaT
 
     def test_td_add_timestamp_overflow(self):
-        msg = "int too (large|big) to convert"
-        with pytest.raises(OverflowError, match=msg):
+        msg = "Cannot cast 259987 from D to 'ns' without overflow"
+        with pytest.raises(OutOfBoundsTimedelta, match=msg):
             Timestamp("1700-01-01") + Timedelta(13 * 19999, unit="D")
 
         msg = "Cannot cast 259987 days, 0:00:00 to unit=ns without overflow"

pandas/tests/scalar/timedelta/test_constructors.py

@@ -13,6 +13,15 @@
 )
 
 
+def test_construct_with_weeks_unit_overflow():
+    # GH#47268 don't silently wrap around
+    with pytest.raises(OutOfBoundsTimedelta, match="without overflow"):
+        Timedelta(1000000000000000000, unit="W")
+
+    with pytest.raises(OutOfBoundsTimedelta, match="without overflow"):
+        Timedelta(1000000000000000000.0, unit="W")
+
+
 def test_construct_from_td64_with_unit():
     # ignore the unit, as it may cause silently overflows leading to incorrect
     #  results, and in non-overflow cases is irrelevant GH#46827
@@ -204,15 +213,15 @@ def test_td_from_repr_roundtrip(val):
 
 
 def test_overflow_on_construction():
-    msg = "int too (large|big) to convert"
-
     # GH#3374
     value = Timedelta("1day").value * 20169940
-    with pytest.raises(OverflowError, match=msg):
+    msg = "Cannot cast 1742682816000000000000 from ns to 'ns' without overflow"
+    with pytest.raises(OutOfBoundsTimedelta, match=msg):
         Timedelta(value)
 
     # xref GH#17637
-    with pytest.raises(OverflowError, match=msg):
+    msg = "Cannot cast 139993 from D to 'ns' without overflow"
+    with pytest.raises(OutOfBoundsTimedelta, match=msg):
         Timedelta(7 * 19999, unit="D")
 
     msg = "Cannot cast 259987 days, 0:00:00 to unit=ns without overflow"

pandas/tests/scalar/timedelta/test_timedelta.py

@@ -744,10 +744,12 @@ def test_implementation_limits(self):
         td = Timedelta(min_td.value - 1, "ns")
         assert td is NaT
 
-        with pytest.raises(OverflowError, match=msg):
+        msg = "Cannot cast -9223372036854775809 from ns to 'ns' without overflow"
+        with pytest.raises(OutOfBoundsTimedelta, match=msg):
             Timedelta(min_td.value - 2, "ns")
 
-        with pytest.raises(OverflowError, match=msg):
+        msg = "Cannot cast 9223372036854775808 from ns to 'ns' without overflow"
+        with pytest.raises(OutOfBoundsTimedelta, match=msg):
             Timedelta(max_td.value + 1, "ns")
 
     def test_total_seconds_precision(self):