Comparison for timedelta, time, date and datetime objects: __eq__ and

__ne__ no longer complain if they don't know how to compare to the other
thing.  If no meaningful way to compare is known, saying "not equal" is
sensible.  This allows things like

    if adatetime in some_sequence:
and
    somedict[adatetime] = whatever

to work as expected even if some_sequence contains non-datetime objects,
or somedict non-datetime keys, because they only call __eq__.

It still complains (raises TypeError) for mixed-type comparisons in
contexts that require a total ordering, such as list.sort(), use as a
key in a BTree-based data structure, and cmp().

1 files changed, 52 insertions, 38 deletions

diff --git a/Modules/datetimemodule.c b/Modules/datetimemodule.c
index fa9e3a1..c8ef3ae 100644
--- a/Modules/datetimemodule.c
+++ b/Modules/datetimemodule.c
@@ -1224,6 +1224,16 @@ diff_to_bool(int diff, int op)
 	return result;
 }
 
+/* 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",
+		     a->ob_type->tp_name, b->ob_type->tp_name);
+	return NULL;
+}
+
 /* ---------------------------------------------------------------------------
  * Basic object allocation.  These allocate Python objects of the right
  * size and type, and do the Python object-initialization bit.  If there's
@@ -1654,21 +1664,23 @@ delta_subtract(PyObject *left, PyObject *right)
 static PyObject *
 delta_richcompare(PyDateTime_Delta *self, PyObject *other, int op)
 {
-	int diff;
+	int diff = 42;	/* nonsense */
 
-	if (! PyDelta_CheckExact(other)) {
-		PyErr_Format(PyExc_TypeError,
-			     "can't compare %s to %s instance",
-			     self->ob_type->tp_name, other->ob_type->tp_name);
-		return NULL;
-	}
-	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);
+	if (PyDelta_CheckExact(other)) {
+		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);
+		}
 	}
+	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);
 }
 
@@ -2443,23 +2455,23 @@ date_isocalendar(PyDateTime_Date *self)
 static PyObject *
 date_richcompare(PyDateTime_Date *self, PyObject *other, int op)
 {
-	int diff;
+	int diff = 42;	/* nonsense */
 
-	if (! PyDate_Check(other)) {
-		if (PyObject_HasAttrString(other, "timetuple")) {
-			/* A hook for other kinds of date objects. */
-			Py_INCREF(Py_NotImplemented);
-			return Py_NotImplemented;
-		}
-		/* Stop this from falling back to address comparison. */
-		PyErr_Format(PyExc_TypeError,
-			     "can't compare '%s' to '%s'",
-			     self->ob_type->tp_name,
-			     other->ob_type->tp_name);
-		return NULL;
+	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. */
+		Py_INCREF(Py_NotImplemented);
+		return Py_NotImplemented;
 	}
-	diff = memcmp(self->data, ((PyDateTime_Date *)other)->data,
-		      _PyDateTime_DATE_DATASIZE);
+	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);
 }
 
@@ -3173,12 +3185,13 @@ time_richcompare(PyDateTime_Time *self, PyObject *other, int op)
 	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. */
-		PyErr_Format(PyExc_TypeError,
-			     "can't compare '%s' to '%s'",
-			     self->ob_type->tp_name,
-			     other->ob_type->tp_name);
-		return NULL;
+		return cmperror((PyObject *)self, other);
 	}
 	if (classify_two_utcoffsets((PyObject *)self, &offset1, &n1, Py_None,
 				     other, &offset2, &n2, Py_None) < 0)
@@ -4011,12 +4024,13 @@ datetime_richcompare(PyDateTime_DateTime *self, PyObject *other, int op)
 			Py_INCREF(Py_NotImplemented);
 			return Py_NotImplemented;
 		}
+		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. */
-		PyErr_Format(PyExc_TypeError,
-			     "can't compare '%s' to '%s'",
-			     self->ob_type->tp_name,
-			     other->ob_type->tp_name);
-		return NULL;
+		return cmperror((PyObject *)self, other);
 	}
 
 	if (classify_two_utcoffsets((PyObject *)self, &offset1, &n1,