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Fix the datetime comparison conundrum. 

The special-casing of other objects with a timetuple attribute is gone.
Let's hope Tim agrees.
This commit is contained in:
Guido van Rossum 2006-08-24 17:29:38 +00:00
parent b6bb0c79d9
commit 19960597ad
2 changed files with 97 additions and 117 deletions
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81
Lib/test/test_datetime.py
View File

@ -954,41 +954,60 @@ class TestDate(HarmlessMixedComparison):
def test_mixed_compare(self):
our = self.theclass(2000, 4, 5)
# Our class can be compared for equality to other classes
self.assertEqual(our == 1, False)
self.assertEqual(1 == our, False)
self.assertEqual(our != 1, True)
self.assertEqual(1 != our, True)
# But the ordering is undefined
self.assertRaises(TypeError, lambda: our < 1)
self.assertRaises(TypeError, lambda: 1 < our)
self.assertRaises(TypeError, cmp, our, 1)
self.assertRaises(TypeError, cmp, 1, our)
class AnotherDateTimeClass(object):
def __cmp__(self, other):
# Return "equal" so calling this can't be confused with
# compare-by-address (which never says "equal" for distinct
# objects).
return 0
# Repeat those tests with a different class
# This still errors, because date and datetime comparison raise
# TypeError instead of NotImplemented when they don't know what to
# do, in order to stop comparison from falling back to the default
# compare-by-address.
their = AnotherDateTimeClass()
class SomeClass:
pass
their = SomeClass()
self.assertEqual(our == their, False)
self.assertEqual(their == our, False)
self.assertEqual(our != their, True)
self.assertEqual(their != our, True)
self.assertRaises(TypeError, lambda: our < their)
self.assertRaises(TypeError, lambda: their < our)
self.assertRaises(TypeError, cmp, our, their)
# Oops: The next stab raises TypeError in the C implementation,
# but not in the Python implementation of datetime. The difference
# is due to that the Python implementation defines __cmp__ but
# the C implementation defines tp_richcompare. This is more pain
# to fix than it's worth, so commenting out the test.
# self.assertEqual(cmp(their, our), 0)
self.assertRaises(TypeError, cmp, their, our)
# But date and datetime comparison return NotImplemented instead if the
# other object has a timetuple attr. This gives the other object a
# chance to do the comparison.
class Comparable(AnotherDateTimeClass):
def timetuple(self):
return ()
# However, if the other class explicitly defines ordering
# relative to our class, it is allowed to do so
their = Comparable()
self.assertEqual(cmp(our, their), 0)
self.assertEqual(cmp(their, our), 0)
self.failUnless(our == their)
self.failUnless(their == our)
class LargerThanAnything:
def __lt__(self, other):
return False
def __le__(self, other):
return isinstance(other, LargerThanAnything)
def __eq__(self, other):
return isinstance(other, LargerThanAnything)
def __ne__(self, other):
return not isinstance(other, LargerThanAnything)
def __gt__(self, other):
return not isinstance(other, LargerThanAnything)
def __ge__(self, other):
return True
their = LargerThanAnything()
self.assertEqual(our == their, False)
self.assertEqual(their == our, False)
self.assertEqual(our != their, True)
self.assertEqual(their != our, True)
self.assertEqual(our < their, True)
self.assertEqual(their < our, False)
self.assertEqual(cmp(our, their), -1)
self.assertEqual(cmp(their, our), 1)
def test_bool(self):
# All dates are considered true.
@ -3217,10 +3236,10 @@ class Oddballs(unittest.TestCase):
# Neverthelss, comparison should work with the base-class (date)
# projection if use of a date method is forced.
self.assert_(as_date.__eq__(as_datetime))
self.assertEqual(as_date.__eq__(as_datetime), True)
different_day = (as_date.day + 1) % 20 + 1
self.assert_(not as_date.__eq__(as_datetime.replace(day=
different_day)))
as_different = as_datetime.replace(day= different_day)
self.assertEqual(as_date.__eq__(as_different), False)
# 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.

133
Modules/datetimemodule.c
View File

@ -1387,7 +1387,7 @@ build_struct_time(int y, int m, int d, int hh, int mm, int ss, int dstflag)
* Miscellaneous helpers.
*/
/* For obscure reasons, we need to use tp_richcompare instead of tp_compare.
/* For various reasons, we need to use tp_richcompare instead of tp_compare.
* The comparisons here all most naturally compute a cmp()-like result.
* This little helper turns that into a bool result for rich comparisons.
*/
@ -1705,31 +1705,23 @@ delta_subtract(PyObject *left, PyObject *right)
return result;
}
/* This is more natural as a tp_compare, but doesn't work then: for whatever
* reason, Python's try_3way_compare ignores tp_compare unless
* PyInstance_Check returns true, but these aren't old-style classes.
*/
static PyObject *
delta_richcompare(PyDateTime_Delta *self, PyObject *other, int op)
delta_richcompare(PyObject *self, PyObject *other, int op)
{
int diff = 42; /* nonsense */
if (PyDelta_Check(other)) {
diff = GET_TD_DAYS(self) - GET_TD_DAYS(other);
int diff = GET_TD_DAYS(self) - GET_TD_DAYS(other);
if (diff == 0) {
diff = GET_TD_SECONDS(self) - GET_TD_SECONDS(other);
if (diff == 0)
diff = GET_TD_MICROSECONDS(self) -
GET_TD_MICROSECONDS(other);
}
return diff_to_bool(diff, op);
}
else {
Py_INCREF(Py_NotImplemented);
return Py_NotImplemented;
}
else if (op == Py_EQ || op == Py_NE)
diff = 1; /* any non-zero value will do */
else /* stop this from falling back to address comparison */
return cmperror((PyObject *)self, other);
return diff_to_bool(diff, op);
}
static PyObject *delta_getstate(PyDateTime_Delta *self);
@ -2145,7 +2137,7 @@ static PyTypeObject PyDateTime_DeltaType = {
delta_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
(richcmpfunc)delta_richcompare, /* tp_richcompare */
delta_richcompare, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
@ -2499,31 +2491,19 @@ date_isocalendar(PyDateTime_Date *self)
/* Miscellaneous methods. */
/* This is more natural as a tp_compare, but doesn't work then: for whatever
* reason, Python's try_3way_compare ignores tp_compare unless
* PyInstance_Check returns true, but these aren't old-style classes.
*/
static PyObject *
date_richcompare(PyDateTime_Date *self, PyObject *other, int op)
date_richcompare(PyObject *self, PyObject *other, int op)
{
int diff = 42; /* nonsense */
if (PyDate_Check(other))
diff = memcmp(self->data, ((PyDateTime_Date *)other)->data,
_PyDateTime_DATE_DATASIZE);
else if (PyObject_HasAttrString(other, "timetuple")) {
/* A hook for other kinds of date objects. */
if (PyDate_Check(other)) {
int diff = memcmp(((PyDateTime_Date *)self)->data,
((PyDateTime_Date *)other)->data,
_PyDateTime_DATE_DATASIZE);
return diff_to_bool(diff, op);
}
else {
Py_INCREF(Py_NotImplemented);
return Py_NotImplemented;
}
else if (op == Py_EQ || op == Py_NE)
diff = 1; /* any non-zero value will do */
else /* stop this from falling back to address comparison */
return cmperror((PyObject *)self, other);
return diff_to_bool(diff, op);
}
static PyObject *
@ -2701,7 +2681,7 @@ static PyTypeObject PyDateTime_DateType = {
date_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
(richcmpfunc)date_richcompare, /* tp_richcompare */
date_richcompare, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
@ -3223,28 +3203,19 @@ time_strftime(PyDateTime_Time *self, PyObject *args, PyObject *kw)
* Miscellaneous methods.
*/
/* This is more natural as a tp_compare, but doesn't work then: for whatever
* reason, Python's try_3way_compare ignores tp_compare unless
* PyInstance_Check returns true, but these aren't old-style classes.
*/
static PyObject *
time_richcompare(PyDateTime_Time *self, PyObject *other, int op)
time_richcompare(PyObject *self, PyObject *other, int op)
{
int diff;
naivety n1, n2;
int offset1, offset2;
if (! PyTime_Check(other)) {
if (op == Py_EQ || op == Py_NE) {
PyObject *result = op == Py_EQ ? Py_False : Py_True;
Py_INCREF(result);
return result;
}
/* Stop this from falling back to address comparison. */
return cmperror((PyObject *)self, other);
Py_INCREF(Py_NotImplemented);
return Py_NotImplemented;
}
if (classify_two_utcoffsets((PyObject *)self, &offset1, &n1, Py_None,
other, &offset2, &n2, Py_None) < 0)
if (classify_two_utcoffsets(self, &offset1, &n1, Py_None,
other, &offset2, &n2, Py_None) < 0)
return NULL;
assert(n1 != OFFSET_UNKNOWN && n2 != OFFSET_UNKNOWN);
/* If they're both naive, or both aware and have the same offsets,
@ -3252,7 +3223,8 @@ time_richcompare(PyDateTime_Time *self, PyObject *other, int op)
* offset2 == 0 at this point.
*/
if (n1 == n2 && offset1 == offset2) {
diff = memcmp(self->data, ((PyDateTime_Time *)other)->data,
diff = memcmp(((PyDateTime_Time *)self)->data,
((PyDateTime_Time *)other)->data,
_PyDateTime_TIME_DATASIZE);
return diff_to_bool(diff, op);
}
@ -3474,7 +3446,7 @@ static PyTypeObject PyDateTime_TimeType = {
time_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
(richcmpfunc)time_richcompare, /* tp_richcompare */
time_richcompare, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
@ -4115,46 +4087,34 @@ datetime_ctime(PyDateTime_DateTime *self)
/* Miscellaneous methods. */
/* This is more natural as a tp_compare, but doesn't work then: for whatever
* reason, Python's try_3way_compare ignores tp_compare unless
* PyInstance_Check returns true, but these aren't old-style classes.
*/
static PyObject *
datetime_richcompare(PyDateTime_DateTime *self, PyObject *other, int op)
datetime_richcompare(PyObject *self, PyObject *other, int op)
{
int diff;
naivety n1, n2;
int offset1, offset2;
if (! PyDateTime_Check(other)) {
/* If other has a "timetuple" attr, that's an advertised
* hook for other classes to ask to get comparison control.
* However, date instances have a timetuple attr, and we
* don't want to allow that comparison. Because datetime
* is a subclass of date, when mixing date and datetime
* in a comparison, Python gives datetime the first shot
* (it's the more specific subtype). So we can stop that
* combination here reliably.
*/
if (PyObject_HasAttrString(other, "timetuple") &&
! PyDate_Check(other)) {
/* A hook for other kinds of datetime objects. */
Py_INCREF(Py_NotImplemented);
return Py_NotImplemented;
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 (op == Py_EQ || op == Py_NE) {
PyObject *result = op == Py_EQ ? Py_False : Py_True;
Py_INCREF(result);
return result;
}
/* Stop this from falling back to address comparison. */
return cmperror((PyObject *)self, other);
Py_INCREF(Py_NotImplemented);
return Py_NotImplemented;
}
if (classify_two_utcoffsets((PyObject *)self, &offset1, &n1,
(PyObject *)self,
other, &offset2, &n2,
other) < 0)
if (classify_two_utcoffsets(self, &offset1, &n1, self,
other, &offset2, &n2, other) < 0)
return NULL;
assert(n1 != OFFSET_UNKNOWN && n2 != OFFSET_UNKNOWN);
/* If they're both naive, or both aware and have the same offsets,
@ -4162,7 +4122,8 @@ datetime_richcompare(PyDateTime_DateTime *self, PyObject *other, int op)
* offset2 == 0 at this point.
*/
if (n1 == n2 && offset1 == offset2) {
diff = memcmp(self->data, ((PyDateTime_DateTime *)other)->data,
diff = memcmp(((PyDateTime_DateTime *)self)->data,
((PyDateTime_DateTime *)other)->data,
_PyDateTime_DATETIME_DATASIZE);
return diff_to_bool(diff, op);
}
@ -4568,7 +4529,7 @@ static PyTypeObject PyDateTime_DateTimeType = {
datetime_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
(richcmpfunc)datetime_richcompare, /* tp_richcompare */
datetime_richcompare, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */