From b1043607884d774acabd255ecdcebb159f76a2fb Mon Sep 17 00:00:00 2001 From: Serhiy Storchaka Date: Sun, 11 Feb 2024 13:06:43 +0200 Subject: [PATCH] gh-49766: Make date-datetime comparison more symmetric and flexible (GH-114760) Now the special comparison methods like `__eq__` and `__lt__` return NotImplemented if one of comparands is date and other is datetime instead of ignoring the time part and the time zone or forcefully return "not equal" or raise TypeError. It makes comparison of date and datetime subclasses more symmetric and allows to change the default behavior by overriding the special comparison methods in subclasses. It is now the same as if date and datetime was independent classes. --- Doc/library/datetime.rst | 32 ++++++++-- Lib/_pydatetime.py | 35 ++++------ Lib/test/datetimetester.py | 64 +++++++++++-------- ...4-01-30-22-10-50.gh-issue-49766.yulJL_.rst | 8 +++ Modules/_datetimemodule.c | 36 +++-------- 5 files changed, 91 insertions(+), 84 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2024-01-30-22-10-50.gh-issue-49766.yulJL_.rst diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst index 930af6cbbe9e8d..a46eed35ee2329 100644 --- a/Doc/library/datetime.rst +++ b/Doc/library/datetime.rst @@ -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() diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py index 54c12d3b2f3f16..b7d569cc41740e 100644 --- a/Lib/_pydatetime.py +++ b/Lib/_pydatetime.py @@ -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) diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py index 53ad5e57ada017..980a8e6c1b1836 100644 --- a/Lib/test/datetimetester.py +++ b/Lib/test/datetimetester.py @@ -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 new file mode 100644 index 00000000000000..eaaa3ba1cb6f09 --- /dev/null +++ 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. diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c index 9b8e0a719d9048..b984ea61b82f0f 100644 --- a/Modules/_datetimemodule.c +++ b/Modules/_datetimemodule.c @@ -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; }