python · serhiy-storchaka · Feb 11, 2024 · Jan 30, 2024 · Feb 2, 2024 · Feb 2, 2024
@@ -619,11 +619,27 @@ Notes:
 (4)
    :class:`date` objects are equal if they represent the same date.
 
+   :class:`!date` objects that are not also :class:`.datetime` instances
+   are never equal to :class:`!datetime` objects, even if they represent
+   the same date.
+
 (5)
    *date1* is considered less than *date2* when *date1* precedes *date2* in time.
    In other words, ``date1 < date2`` if and only if ``date1.toordinal() <
    date2.toordinal()``.
 
+   Order comparison between a :class:`!date` object that is not also a
+   :class:`.datetime` instance and a :class:`!datetime` object raises
+   :exc:`TypeError`.
+
+.. versionchanged:: 3.13
+   Comparison between :class:`.datetime` object and an instance of
+   the :class:`date` subclass that is not a :class:`!datetime` subclass
+   no longer coverts the latter to :class:`!date`, ignoring the time part
+   and the time zone.
+   The default behavior can be changed by overriding the special comparison
+   methods in subclasses.
+
 In Boolean contexts, all :class:`date` objects are considered to be true.
 
 Instance methods:
@@ -1192,9 +1208,6 @@ Supported operations:
    and time, taking into account the time zone.
 
    Naive and aware :class:`!datetime` objects are never equal.
-   :class:`!datetime` objects are never equal to :class:`date` objects
-   that are not also :class:`!datetime` instances, even if they represent
-   the same date.
 
    If both comparands are aware and have different :attr:`~.datetime.tzinfo`
    attributes, the comparison acts as comparands were first converted to UTC
@@ -1206,9 +1219,8 @@ Supported operations:
    *datetime1* is considered less than *datetime2* when *datetime1* precedes
    *datetime2* in time, taking into account the time zone.
 
-   Order comparison between naive and aware :class:`.datetime` objects,
-   as well as a :class:`!datetime` object and a :class:`!date` object
-   that is not also a :class:`!datetime` instance, raises :exc:`TypeError`.
+   Order comparison between naive and aware :class:`.datetime` objects
+   raises :exc:`TypeError`.
 
    If both comparands are aware and have different :attr:`~.datetime.tzinfo`
    attributes, the comparison acts as comparands were first converted to UTC
@@ -1218,6 +1230,14 @@ Supported operations:
    Equality comparisons between aware and naive :class:`.datetime`
    instances don't raise :exc:`TypeError`.
 
+.. versionchanged:: 3.13
+   Comparison between :class:`.datetime` object and an instance of
+   the :class:`date` subclass that is not a :class:`!datetime` subclass
+   no longer coverts the latter to :class:`!date`, ignoring the time part
+   and the time zone.
+   The default behavior can be changed by overriding the special comparison
+   methods in subclasses.
+
 Instance methods:
 
 .. method:: datetime.date()

@@ -556,10 +556,6 @@ def _check_tzinfo_arg(tz):
     if tz is not None and not isinstance(tz, tzinfo):
         raise TypeError("tzinfo argument must be None or of a tzinfo subclass")
 
-def _cmperror(x, y):
-    raise TypeError("can't compare '%s' to '%s'" % (
-                    type(x).__name__, type(y).__name__))
-
 def _divide_and_round(a, b):
     """divide a by b and round result to the nearest integer
 
@@ -1113,32 +1109,33 @@ def replace(self, year=None, month=None, day=None):
     # Comparisons of date objects with other.
 
     def __eq__(self, other):
-        if isinstance(other, date):
+        if isinstance(other, date) and not isinstance(other, datetime):
             return self._cmp(other) == 0
         return NotImplemented
 
     def __le__(self, other):
-        if isinstance(other, date):
+        if isinstance(other, date) and not isinstance(other, datetime):
             return self._cmp(other) <= 0
         return NotImplemented
 
     def __lt__(self, other):
-        if isinstance(other, date):
+        if isinstance(other, date) and not isinstance(other, datetime):
             return self._cmp(other) < 0
         return NotImplemented
 
     def __ge__(self, other):
-        if isinstance(other, date):
+        if isinstance(other, date) and not isinstance(other, datetime):
             return self._cmp(other) >= 0
         return NotImplemented
 
     def __gt__(self, other):
-        if isinstance(other, date):
+        if isinstance(other, date) and not isinstance(other, datetime):
             return self._cmp(other) > 0
         return NotImplemented
 
     def _cmp(self, other):
         assert isinstance(other, date)
+        assert not isinstance(other, datetime)
         y, m, d = self._year, self._month, self._day
         y2, m2, d2 = other._year, other._month, other._day
         return _cmp((y, m, d), (y2, m2, d2))
@@ -2137,42 +2134,32 @@ def dst(self):
     def __eq__(self, other):
         if isinstance(other, datetime):
             return self._cmp(other, allow_mixed=True) == 0
-        elif not isinstance(other, date):
-            return NotImplemented
         else:
-            return False
+            return NotImplemented
 
     def __le__(self, other):
         if isinstance(other, datetime):
             return self._cmp(other) <= 0
-        elif not isinstance(other, date):
-            return NotImplemented
         else:
-            _cmperror(self, other)
+            return NotImplemented
 
     def __lt__(self, other):
         if isinstance(other, datetime):
             return self._cmp(other) < 0
-        elif not isinstance(other, date):
-            return NotImplemented
         else:
-            _cmperror(self, other)
+            return NotImplemented
 
     def __ge__(self, other):
         if isinstance(other, datetime):
             return self._cmp(other) >= 0
-        elif not isinstance(other, date):
-            return NotImplemented
         else:
-            _cmperror(self, other)
+            return NotImplemented
 
     def __gt__(self, other):
         if isinstance(other, datetime):
             return self._cmp(other) > 0
-        elif not isinstance(other, date):
-            return NotImplemented
         else:
-            _cmperror(self, other)
+            return NotImplemented
 
     def _cmp(self, other, allow_mixed=False):
         assert isinstance(other, datetime)

@@ -5435,42 +5435,50 @@ def fromutc(self, dt):
 
 class Oddballs(unittest.TestCase):
 
-    def test_bug_1028306(self):
+    def test_date_datetime_comparison(self):
+        # bpo-1028306, bpo-5516 (gh-49766)
         # Trying to compare a date to a datetime should act like a mixed-
         # type comparison, despite that datetime is a subclass of date.
         as_date = date.today()
         as_datetime = datetime.combine(as_date, time())
-        self.assertTrue(as_date != as_datetime)
-        self.assertTrue(as_datetime != as_date)
-        self.assertFalse(as_date == as_datetime)
-        self.assertFalse(as_datetime == as_date)
-        self.assertRaises(TypeError, lambda: as_date < as_datetime)
-        self.assertRaises(TypeError, lambda: as_datetime < as_date)
-        self.assertRaises(TypeError, lambda: as_date <= as_datetime)
-        self.assertRaises(TypeError, lambda: as_datetime <= as_date)
-        self.assertRaises(TypeError, lambda: as_date > as_datetime)
-        self.assertRaises(TypeError, lambda: as_datetime > as_date)
-        self.assertRaises(TypeError, lambda: as_date >= as_datetime)
-        self.assertRaises(TypeError, lambda: as_datetime >= as_date)
-
-        # Nevertheless, comparison should work with the base-class (date)
-        # projection if use of a date method is forced.
-        self.assertEqual(as_date.__eq__(as_datetime), True)
-        different_day = (as_date.day + 1) % 20 + 1
-        as_different = as_datetime.replace(day= different_day)
-        self.assertEqual(as_date.__eq__(as_different), False)
+        date_sc = SubclassDate(as_date.year, as_date.month, as_date.day)
+        datetime_sc = SubclassDatetime(as_date.year, as_date.month,
+                                       as_date.day, 0, 0, 0)
+        for d in (as_date, date_sc):
+            for dt in (as_datetime, datetime_sc):
+                for x, y in (d, dt), (dt, d):
+                    self.assertTrue(x != y)
+                    self.assertFalse(x == y)
+                    self.assertRaises(TypeError, lambda: x < y)
+                    self.assertRaises(TypeError, lambda: x <= y)
+                    self.assertRaises(TypeError, lambda: x > y)
+                    self.assertRaises(TypeError, lambda: x >= y)
 
         # And date should compare with other subclasses of date.  If a
         # subclass wants to stop this, it's up to the subclass to do so.
-        date_sc = SubclassDate(as_date.year, as_date.month, as_date.day)
-        self.assertEqual(as_date, date_sc)
-        self.assertEqual(date_sc, as_date)
-
         # Ditto for datetimes.
-        datetime_sc = SubclassDatetime(as_datetime.year, as_datetime.month,
-                                       as_date.day, 0, 0, 0)
-        self.assertEqual(as_datetime, datetime_sc)
-        self.assertEqual(datetime_sc, as_datetime)
+        for x, y in ((as_date, date_sc),
+                     (date_sc, as_date),
+                     (as_datetime, datetime_sc),
+                     (datetime_sc, as_datetime)):
+            self.assertTrue(x == y)
+            self.assertFalse(x != y)
+            self.assertFalse(x < y)
+            self.assertFalse(x > y)
+            self.assertTrue(x <= y)
+            self.assertTrue(x >= y)
+
+        # Nevertheless, comparison should work if other object is an instance
+        # of date or datetime class with overridden comparison operators.
+        # So special methods should return NotImplemented, as if
+        # date and datetime were independent classes.
+        for x, y in (as_date, as_datetime), (as_datetime, as_date):
+            self.assertEqual(x.__eq__(y), NotImplemented)
+            self.assertEqual(x.__ne__(y), NotImplemented)
+            self.assertEqual(x.__lt__(y), NotImplemented)
+            self.assertEqual(x.__gt__(y), NotImplemented)
+            self.assertEqual(x.__gt__(y), NotImplemented)
+            self.assertEqual(x.__ge__(y), NotImplemented)
 
     def test_extra_attributes(self):
         with self.assertWarns(DeprecationWarning):

diff --git a/Misc/NEWS.d/next/Library/2024-01-30-22-10-50.gh-issue-49766.yulJL_.rst b/Misc/NEWS.d/next/Library/2024-01-30-22-10-50.gh-issue-49766.yulJL_.rst
@@ -0,0 +1,8 @@
+Fix :class:`~datetime.date`-:class:`~datetime.datetime` comparison. Now the
+special comparison methods like ``__eq__`` and ``__lt__`` return
+:data:`NotImplemented` if one of comparands is :class:`!date` and other is
+:class:`!datetime` instead of ignoring the time part and the time zone or
+forcefully return "not equal" or raise :exc:`TypeError`. It makes comparison
+of :class:`!date` and :class:`!datetime` subclasses more symmetric and
+allows to change the default behavior by overriding the special comparison
+methods in subclasses.
@@ -1816,16 +1816,6 @@ diff_to_bool(int diff, int op)
     Py_RETURN_RICHCOMPARE(diff, 0, op);
 }
 
-/* Raises a "can't compare" TypeError and returns NULL. */
-static PyObject *
-cmperror(PyObject *a, PyObject *b)
-{
-    PyErr_Format(PyExc_TypeError,
-                 "can't compare %s to %s",
-                 Py_TYPE(a)->tp_name, Py_TYPE(b)->tp_name);
-    return NULL;
-}
-
 /* ---------------------------------------------------------------------------
  * Class implementations.
  */
@@ -3448,7 +3438,15 @@ date_isocalendar(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 static PyObject *
 date_richcompare(PyObject *self, PyObject *other, int op)
 {
-    if (PyDate_Check(other)) {
+    /* Since DateTime is a subclass of Date, if the other object is
+     * a DateTime, it would compute an equality testing or an ordering
+     * based on the date part alone, and we don't want that.
+     * So return NotImplemented here in that case.
+     * If a subclass wants to change this, it's up to the subclass to do so.
+     * The behavior is the same as if Date and DateTime were independent
+     * classes.
+     */
+    if (PyDate_Check(other) && !PyDateTime_Check(other)) {
         int diff = memcmp(((PyDateTime_Date *)self)->data,
                           ((PyDateTime_Date *)other)->data,
                           _PyDateTime_DATE_DATASIZE);
@@ -5880,21 +5878,7 @@ datetime_richcompare(PyObject *self, PyObject *other, int op)
     PyObject *offset1, *offset2;
     int diff;
 
-    if (! PyDateTime_Check(other)) {
-        if (PyDate_Check(other)) {
-            /* Prevent invocation of date_richcompare.  We want to
-               return NotImplemented here to give the other object
-               a chance.  But since DateTime is a subclass of
-               Date, if the other object is a Date, it would
-               compute an ordering based on the date part alone,
-               and we don't want that.  So force unequal or
-               uncomparable here in that case. */
-            if (op == Py_EQ)
-                Py_RETURN_FALSE;
-            if (op == Py_NE)
-                Py_RETURN_TRUE;
-            return cmperror(self, other);
-        }
+    if (!PyDateTime_Check(other)) {
         Py_RETURN_NOTIMPLEMENTED;
     }