Add set.isdisjoint()

Doc/library/stdtypes.rst

@@ -1467,6 +1467,13 @@ operations:
 
    Test *x* for non-membership in *s*.
 
+.. method:: set.isdisjoint(other)
+
+   Return True if the set has no elements in common with *other*.
+   Sets are disjoint if and only if their interesection is the empty set.
+
+   .. versionadded:: 2.6
+
 .. method:: set.issubset(other)
             set <= other
 

Lib/test/test_set.py

@@ -102,6 +102,20 @@ class TestJointOps(unittest.TestCase):
             self.assertEqual(self.thetype('abcba').intersection(C('ccb')), set('bc'))
             self.assertEqual(self.thetype('abcba').intersection(C('ef')), set(''))
 
+    def test_isdisjoint(self):
+        def f(s1, s2):
+            'Pure python equivalent of isdisjoint()'
+            return not set(s1).intersection(s2)
+        for larg in '', 'a', 'ab', 'abc', 'ababac', 'cdc', 'cc', 'efgfe', 'ccb', 'ef':
+            s1 = self.thetype(larg)
+            for rarg in '', 'a', 'ab', 'abc', 'ababac', 'cdc', 'cc', 'efgfe', 'ccb', 'ef':
+                for C in set, frozenset, dict.fromkeys, str, unicode, list, tuple:
+                    s2 = C(rarg)
+                    actual = s1.isdisjoint(s2)
+                    expected = f(s1, s2)
+                    self.assertEqual(actual, expected)
+                    self.assert_(actual is True or actual is False)
+
     def test_and(self):
         i = self.s.intersection(self.otherword)
         self.assertEqual(self.s & set(self.otherword), i)
@@ -657,6 +671,18 @@ class TestBasicOps(unittest.TestCase):
         result = empty_set & self.set
         self.assertEqual(result, empty_set)
 
+    def test_self_isdisjoint(self):
+        result = self.set.isdisjoint(self.set)
+        self.assertEqual(result, not self.set)
+
+    def test_empty_isdisjoint(self):
+        result = self.set.isdisjoint(empty_set)
+        self.assertEqual(result, True)
+
+    def test_isdisjoint_empty(self):
+        result = empty_set.isdisjoint(self.set)
+        self.assertEqual(result, True)
+
     def test_self_symmetric_difference(self):
         result = self.set ^ self.set
         self.assertEqual(result, empty_set)
@@ -835,6 +861,22 @@ class TestBinaryOps(unittest.TestCase):
         result = self.set & set([8])
         self.assertEqual(result, empty_set)
 
+    def test_isdisjoint_subset(self):
+        result = self.set.isdisjoint(set((2, 4)))
+        self.assertEqual(result, False)
+
+    def test_isdisjoint_superset(self):
+        result = self.set.isdisjoint(set([2, 4, 6, 8]))
+        self.assertEqual(result, False)
+
+    def test_isdisjoint_overlap(self):
+        result = self.set.isdisjoint(set([3, 4, 5]))
+        self.assertEqual(result, False)
+
+    def test_isdisjoint_non_overlap(self):
+        result = self.set.isdisjoint(set([8]))
+        self.assertEqual(result, True)
+
     def test_sym_difference_subset(self):
         result = self.set ^ set((2, 4))
         self.assertEqual(result, set([6]))
@@ -1456,11 +1498,14 @@ class TestVariousIteratorArgs(unittest.TestCase):
     def test_inline_methods(self):
         s = set('november')
         for data in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5), 'december'):
-            for meth in (s.union, s.intersection, s.difference, s.symmetric_difference):
+            for meth in (s.union, s.intersection, s.difference, s.symmetric_difference, s.isdisjoint):
                 for g in (G, I, Ig, L, R):
                     expected = meth(data)
                     actual = meth(G(data))
-                    self.assertEqual(sorted(actual), sorted(expected))
+                    if isinstance(expected, bool):
+                        self.assertEqual(actual, expected)
+                    else:
+                        self.assertEqual(sorted(actual), sorted(expected))
                 self.assertRaises(TypeError, meth, X(s))
                 self.assertRaises(TypeError, meth, N(s))
                 self.assertRaises(ZeroDivisionError, meth, E(s))

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 2.6 alpha 1?
 Core and builtins
 -----------------
 
+- sets and frozensets now have an isdisjoint() method.
+
 - optimize the performance of builtin.sum().
 
 - Fix warnings found by the new version of the Coverity checker.

Objects/setobject.c

@@ -1332,6 +1332,72 @@ set_iand(PySetObject *so, PyObject *other)
 	return (PyObject *)so;
 }
 
+static PyObject *
+set_isdisjoint(PySetObject *so, PyObject *other)
+{
+	PyObject *key, *it, *tmp;
+
+	if ((PyObject *)so == other) {
+		if (PySet_GET_SIZE(so) == 0)
+			Py_RETURN_TRUE;
+		else
+			Py_RETURN_FALSE;
+	}
+
+	if (PyAnySet_CheckExact(other)) {		
+		Py_ssize_t pos = 0;
+		setentry *entry;
+
+		if (PySet_GET_SIZE(other) > PySet_GET_SIZE(so)) {
+			tmp = (PyObject *)so;
+			so = (PySetObject *)other;
+			other = tmp;
+		}
+		while (set_next((PySetObject *)other, &pos, &entry)) {
+			int rv = set_contains_entry(so, entry);
+			if (rv == -1)
+				return NULL;
+			if (rv)
+				Py_RETURN_FALSE;
+		}
+		Py_RETURN_TRUE;
+	}
+
+	it = PyObject_GetIter(other);
+	if (it == NULL)
+		return NULL;
+
+	while ((key = PyIter_Next(it)) != NULL) {
+		int rv;
+		setentry entry;
+		long hash = PyObject_Hash(key);
+
+		Py_DECREF(key);
+		if (hash == -1) {
+			Py_DECREF(it);
+			return NULL;
+		}
+		entry.hash = hash;
+		entry.key = key;
+		rv = set_contains_entry(so, &entry);
+		if (rv == -1) {
+			Py_DECREF(it);
+			return NULL;
+		}
+		if (rv) {
+			Py_DECREF(it);
+			Py_RETURN_FALSE;
+		}
+	}
+	Py_DECREF(it);
+	if (PyErr_Occurred())
+		return NULL;
+	Py_RETURN_TRUE;
+}
+
+PyDoc_STRVAR(isdisjoint_doc,
+"Return True if two sets have a null intersection.");
+
 static int
 set_difference_update_internal(PySetObject *so, PyObject *other)
 {
@@ -1861,6 +1927,8 @@ static PyMethodDef set_methods[] = {
 	 intersection_doc},
 	{"intersection_update",(PyCFunction)set_intersection_update,	METH_O,
 	 intersection_update_doc},
+	{"isdisjoint",	(PyCFunction)set_isdisjoint,	METH_O,
+	 isdisjoint_doc},
 	{"issubset",	(PyCFunction)set_issubset,	METH_O,
 	 issubset_doc},
 	{"issuperset",	(PyCFunction)set_issuperset,	METH_O,
@@ -1984,6 +2052,8 @@ static PyMethodDef frozenset_methods[] = {
 	 difference_doc},
 	{"intersection",(PyCFunction)set_intersection,	METH_O,
 	 intersection_doc},
+	{"isdisjoint",	(PyCFunction)set_isdisjoint,	METH_O,
+	 isdisjoint_doc},
 	{"issubset",	(PyCFunction)set_issubset,	METH_O,
 	 issubset_doc},
 	{"issuperset",	(PyCFunction)set_issuperset,	METH_O,