Issue #2534: speed up isinstance() and issubclass() by 50-70%, so as to

match Python 2.5 speed despite the __instancecheck__ / __subclasscheck__
mechanism. In the process, fix a bug where isinstance() and issubclass(),
when given a tuple of classes as second argument, were looking up
__instancecheck__ / __subclasscheck__ on the tuple rather than on each
type object.

Reviewed by Benjamin Peterson and Raymond Hettinger.

Include/abstract.h

@@ -1273,6 +1273,11 @@ PyAPI_FUNC(int) PyObject_IsSubclass(PyObject *object, PyObject *typeorclass);
       /* issubclass(object, typeorclass) */
 
 
+PyAPI_FUNC(int) _PyObject_RealIsInstance(PyObject *inst, PyObject *cls);
+
+PyAPI_FUNC(int) _PyObject_RealIsSubclass(PyObject *derived, PyObject *cls);
+
+
 #ifdef __cplusplus
 }
 #endif

Lib/test/test_abc.py

@@ -75,15 +75,21 @@ class TestABC(unittest.TestCase):
             pass
         b = B()
         self.assertEqual(issubclass(B, A), False)
+        self.assertEqual(issubclass(B, (A,)), False)
         self.assertEqual(isinstance(b, A), False)
+        self.assertEqual(isinstance(b, (A,)), False)
         A.register(B)
         self.assertEqual(issubclass(B, A), True)
+        self.assertEqual(issubclass(B, (A,)), True)
         self.assertEqual(isinstance(b, A), True)
+        self.assertEqual(isinstance(b, (A,)), True)
         class C(B):
             pass
         c = C()
         self.assertEqual(issubclass(C, A), True)
+        self.assertEqual(issubclass(C, (A,)), True)
         self.assertEqual(isinstance(c, A), True)
+        self.assertEqual(isinstance(c, (A,)), True)
 
     def test_isinstance_invalidation(self):
         class A(metaclass=abc.ABCMeta):
@@ -92,22 +98,29 @@ class TestABC(unittest.TestCase):
             pass
         b = B()
         self.assertEqual(isinstance(b, A), False)
+        self.assertEqual(isinstance(b, (A,)), False)
         A.register(B)
         self.assertEqual(isinstance(b, A), True)
+        self.assertEqual(isinstance(b, (A,)), True)
 
     def test_registration_builtins(self):
         class A(metaclass=abc.ABCMeta):
             pass
         A.register(int)
         self.assertEqual(isinstance(42, A), True)
+        self.assertEqual(isinstance(42, (A,)), True)
         self.assertEqual(issubclass(int, A), True)
+        self.assertEqual(issubclass(int, (A,)), True)
         class B(A):
             pass
         B.register(str)
         class C(str): pass
         self.assertEqual(isinstance("", A), True)
+        self.assertEqual(isinstance("", (A,)), True)
         self.assertEqual(issubclass(str, A), True)
+        self.assertEqual(issubclass(str, (A,)), True)
         self.assertEqual(issubclass(C, A), True)
+        self.assertEqual(issubclass(C, (A,)), True)
 
     def test_registration_edge_cases(self):
         class A(metaclass=abc.ABCMeta):
@@ -130,29 +143,40 @@ class TestABC(unittest.TestCase):
         class A(metaclass=abc.ABCMeta):
             pass
         self.failUnless(issubclass(A, A))
+        self.failUnless(issubclass(A, (A,)))
         class B(metaclass=abc.ABCMeta):
             pass
         self.failIf(issubclass(A, B))
+        self.failIf(issubclass(A, (B,)))
         self.failIf(issubclass(B, A))
+        self.failIf(issubclass(B, (A,)))
         class C(metaclass=abc.ABCMeta):
             pass
         A.register(B)
         class B1(B):
             pass
         self.failUnless(issubclass(B1, A))
+        self.failUnless(issubclass(B1, (A,)))
         class C1(C):
             pass
         B1.register(C1)
         self.failIf(issubclass(C, B))
+        self.failIf(issubclass(C, (B,)))
         self.failIf(issubclass(C, B1))
+        self.failIf(issubclass(C, (B1,)))
         self.failUnless(issubclass(C1, A))
+        self.failUnless(issubclass(C1, (A,)))
         self.failUnless(issubclass(C1, B))
+        self.failUnless(issubclass(C1, (B,)))
         self.failUnless(issubclass(C1, B1))
+        self.failUnless(issubclass(C1, (B1,)))
         C1.register(int)
         class MyInt(int):
             pass
         self.failUnless(issubclass(MyInt, A))
+        self.failUnless(issubclass(MyInt, (A,)))
         self.failUnless(isinstance(42, A))
+        self.failUnless(isinstance(42, (A,)))
 
     def test_all_new_methods_are_called(self):
         class A(metaclass=abc.ABCMeta):

Lib/test/test_exceptions.py

@@ -582,12 +582,18 @@ class ExceptionTests(unittest.TestCase):
             except KeyError:
                 pass
             except:
-                self.fail("Should have raised TypeError")
+                self.fail("Should have raised KeyError")
             else:
-                self.fail("Should have raised TypeError")
-        self.assertEqual(stderr.getvalue(),
-                         "Exception ValueError: ValueError() "
-                         "in <class 'KeyError'> ignored\n")
+                self.fail("Should have raised KeyError")
+
+        def g():
+            try:
+                return g()
+            except RuntimeError:
+                return sys.exc_info()
+        e, v, tb = g()
+        self.assert_(isinstance(v, RuntimeError), type(v))
+        self.assert_("maximum recursion depth exceeded" in str(v), str(v))
 
 
     def test_MemoryError(self):

Lib/test/test_typechecks.py

@@ -33,26 +33,39 @@ class TypeChecksTest(unittest.TestCase):
 
     def testIsSubclassBuiltin(self):
         self.assertEqual(issubclass(int, Integer), True)
+        self.assertEqual(issubclass(int, (Integer,)), True)
         self.assertEqual(issubclass(float, Integer), False)
+        self.assertEqual(issubclass(float, (Integer,)), False)
 
     def testIsInstanceBuiltin(self):
         self.assertEqual(isinstance(42, Integer), True)
+        self.assertEqual(isinstance(42, (Integer,)), True)
         self.assertEqual(isinstance(3.14, Integer), False)
+        self.assertEqual(isinstance(3.14, (Integer,)), False)
 
     def testIsInstanceActual(self):
         self.assertEqual(isinstance(Integer(), Integer), True)
+        self.assertEqual(isinstance(Integer(), (Integer,)), True)
 
     def testIsSubclassActual(self):
         self.assertEqual(issubclass(Integer, Integer), True)
+        self.assertEqual(issubclass(Integer, (Integer,)), True)
 
     def testSubclassBehavior(self):
         self.assertEqual(issubclass(SubInt, Integer), True)
+        self.assertEqual(issubclass(SubInt, (Integer,)), True)
         self.assertEqual(issubclass(SubInt, SubInt), True)
+        self.assertEqual(issubclass(SubInt, (SubInt,)), True)
         self.assertEqual(issubclass(Integer, SubInt), False)
+        self.assertEqual(issubclass(Integer, (SubInt,)), False)
         self.assertEqual(issubclass(int, SubInt), False)
+        self.assertEqual(issubclass(int, (SubInt,)), False)
         self.assertEqual(isinstance(SubInt(), Integer), True)
+        self.assertEqual(isinstance(SubInt(), (Integer,)), True)
         self.assertEqual(isinstance(SubInt(), SubInt), True)
+        self.assertEqual(isinstance(SubInt(), (SubInt,)), True)
         self.assertEqual(isinstance(42, SubInt), False)
+        self.assertEqual(isinstance(42, (SubInt,)), False)
 
 
 def test_main():

Misc/NEWS

@@ -12,6 +12,13 @@ What's New in Python 3.0 release candidate 1
 Core and Builtins
 -----------------
 
+- Issue #2534: speed up isinstance() and issubclass() by 50-70%, so as to 
+  match Python 2.5 speed despite the __instancecheck__ / __subclasscheck__
+  mechanism. In the process, fix a bug where isinstance() and issubclass(),
+  when given a tuple of classes as second argument, were looking up
+  __instancecheck__ / __subclasscheck__ on the tuple rather than on each
+  type object.
+
 - Issue #3663: Py_None was decref'd when printing SyntaxErrors.
 
 - Issue #3657: Fix uninitialized memory read when pickling longs.

Objects/abstract.c

@@ -2474,39 +2474,38 @@ abstract_get_bases(PyObject *cls)
 static int
 abstract_issubclass(PyObject *derived, PyObject *cls)
 {
-	PyObject *bases;
+	PyObject *bases = NULL;
 	Py_ssize_t i, n;
 	int r = 0;
 
-
-	if (derived == cls)
-		return 1;
-
-	if (PyTuple_Check(cls)) {
-		/* Not a general sequence -- that opens up the road to
-		   recursion and stack overflow. */
-		n = PyTuple_GET_SIZE(cls);
+	while (1) {
+		if (derived == cls)
+			return 1;
+		bases = abstract_get_bases(derived);
+		if (bases == NULL) {
+			if (PyErr_Occurred())
+				return -1;
+			return 0;
+		}
+		n = PyTuple_GET_SIZE(bases);
+		if (n == 0) {
+			Py_DECREF(bases);
+			return 0;
+		}
+		/* Avoid recursivity in the single inheritance case */
+		if (n == 1) {
+			derived = PyTuple_GET_ITEM(bases, 0);
+			Py_DECREF(bases);
+			continue;
+		}
 		for (i = 0; i < n; i++) {
-			if (derived == PyTuple_GET_ITEM(cls, i))
-				return 1;
+			r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls);
+			if (r != 0)
+				break;
 		}
+		Py_DECREF(bases);
+		return r;
 	}
-	bases = abstract_get_bases(derived);
-	if (bases == NULL) {
-		if (PyErr_Occurred())
-			return -1;
-		return 0;
-	}
-	n = PyTuple_GET_SIZE(bases);
-	for (i = 0; i < n; i++) {
-		r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls);
-		if (r != 0)
-			break;
-	}
-
-	Py_DECREF(bases);
-
-	return r;
 }
 
 static int
@@ -2524,7 +2523,7 @@ check_class(PyObject *cls, const char *error)
 }
 
 static int
-recursive_isinstance(PyObject *inst, PyObject *cls, int recursion_depth)
+recursive_isinstance(PyObject *inst, PyObject *cls)
 {
 	PyObject *icls;
 	static PyObject *__class__ = NULL;
@@ -2553,25 +2552,6 @@ recursive_isinstance(PyObject *inst, PyObject *cls, int recursion_depth)
 			}
 		}
 	}
-	else if (PyTuple_Check(cls)) {
-		Py_ssize_t i, n;
-
-		if (!recursion_depth) {
-		    PyErr_SetString(PyExc_RuntimeError,
-				    "nest level of tuple too deep");
-		    return -1;
-		}
-
-		n = PyTuple_GET_SIZE(cls);
-		for (i = 0; i < n; i++) {
-			retval = recursive_isinstance(
-				    inst,
-				    PyTuple_GET_ITEM(cls, i),
-				    recursion_depth-1);
-			if (retval != 0)
-				break;
-		}
-	}
 	else {
 		if (!check_class(cls,
 			"isinstance() arg 2 must be a class, type,"
@@ -2601,6 +2581,24 @@ PyObject_IsInstance(PyObject *inst, PyObject *cls)
 	if (Py_TYPE(inst) == (PyTypeObject *)cls)
 		return 1;
 
+	if (PyTuple_Check(cls)) {
+		Py_ssize_t i;
+		Py_ssize_t n;
+		int r = 0;
+
+		if (Py_EnterRecursiveCall(" in __instancecheck__"))
+			return -1;
+		n = PyTuple_GET_SIZE(cls);
+		for (i = 0; i < n; ++i) {
+			PyObject *item = PyTuple_GET_ITEM(cls, i);
+			r = PyObject_IsInstance(inst, item);
+			if (r != 0)
+				/* either found it, or got an error */
+				break;
+		}
+		Py_LeaveRecursiveCall();
+		return r;
+	}
 	if (name == NULL) {
 		name = PyUnicode_InternFromString("__instancecheck__");
 		if (name == NULL)
@@ -2625,51 +2623,25 @@ PyObject_IsInstance(PyObject *inst, PyObject *cls)
 		}
 		return ok;
 	}
-	return recursive_isinstance(inst, cls, Py_GetRecursionLimit());
+	return recursive_isinstance(inst, cls);
 }
 
 static	int
-recursive_issubclass(PyObject *derived, PyObject *cls, int recursion_depth)
+recursive_issubclass(PyObject *derived, PyObject *cls)
 {
-	int retval;
-
-	{
-		if (!check_class(derived,
-				 "issubclass() arg 1 must be a class"))
-			return -1;
-
-		if (PyTuple_Check(cls)) {
-			Py_ssize_t i;
-			Py_ssize_t n = PyTuple_GET_SIZE(cls);
-
-			if (!recursion_depth) {
-			    PyErr_SetString(PyExc_RuntimeError,
-					    "nest level of tuple too deep");
-			    return -1;
-			}
-			for (i = 0; i < n; ++i) {
-				retval = recursive_issubclass(
-					    derived,
-					    PyTuple_GET_ITEM(cls, i),
-					    recursion_depth-1);
-				if (retval != 0) {
-					/* either found it, or got an error */
-					return retval;
-				}
-			}
-			return 0;
-		}
-		else {
-			if (!check_class(cls,
-					"issubclass() arg 2 must be a class"
-					" or tuple of classes"))
-				return -1;
-		}
-
-		retval = abstract_issubclass(derived, cls);
+	if (PyType_Check(cls) && PyType_Check(derived)) {
+		/* Fast path (non-recursive) */
+		return PyType_IsSubtype((PyTypeObject *)derived, (PyTypeObject *)cls);
 	}
+	if (!check_class(derived,
+			 "issubclass() arg 1 must be a class"))
+		return -1;
+	if (!check_class(cls,
+			"issubclass() arg 2 must be a class"
+			" or tuple of classes"))
+		return -1;
 
-	return retval;
+	return abstract_issubclass(derived, cls);
 }
 
 int
@@ -2678,20 +2650,40 @@ PyObject_IsSubclass(PyObject *derived, PyObject *cls)
 	static PyObject *name = NULL;
 	PyObject *t, *v, *tb;
 	PyObject *checker;
-	PyErr_Fetch(&t, &v, &tb);
 	
+	if (PyTuple_Check(cls)) {
+		Py_ssize_t i;
+		Py_ssize_t n;
+		int r = 0;
+
+		if (Py_EnterRecursiveCall(" in __subclasscheck__"))
+			return -1;
+		n = PyTuple_GET_SIZE(cls);
+		for (i = 0; i < n; ++i) {
+			PyObject *item = PyTuple_GET_ITEM(cls, i);
+			r = PyObject_IsSubclass(derived, item);
+			if (r != 0)
+				/* either found it, or got an error */
+				break;
+		}
+		Py_LeaveRecursiveCall();
+		return r;
+	}
 	if (name == NULL) {
 		name = PyUnicode_InternFromString("__subclasscheck__");
 		if (name == NULL)
 			return -1;
 	}
+	PyErr_Fetch(&t, &v, &tb);
 	checker = PyObject_GetAttr(cls, name);
 	PyErr_Restore(t, v, tb);
 	if (checker != NULL) {
 		PyObject *res;
 		int ok = -1;
-		if (Py_EnterRecursiveCall(" in __subclasscheck__"))
+		if (Py_EnterRecursiveCall(" in __subclasscheck__")) {
+			Py_DECREF(checker);
 			return ok;
+		}
 		res = PyObject_CallFunctionObjArgs(checker, derived, NULL);
 		Py_LeaveRecursiveCall();
 		Py_DECREF(checker);
@@ -2701,7 +2693,19 @@ PyObject_IsSubclass(PyObject *derived, PyObject *cls)
 		}
 		return ok;
 	}
-	return recursive_issubclass(derived, cls, Py_GetRecursionLimit());
+	return recursive_issubclass(derived, cls);
+}
+
+int
+_PyObject_RealIsInstance(PyObject *inst, PyObject *cls)
+{
+	return recursive_isinstance(inst, cls);
+}
+
+int
+_PyObject_RealIsSubclass(PyObject *derived, PyObject *cls)
+{
+	return recursive_issubclass(derived, cls);
 }
 
 

Objects/typeobject.c

@@ -584,6 +584,49 @@ type_get_doc(PyTypeObject *type, void *context)
 	return result;
 }
 
+static PyObject *
+type___instancecheck__(PyObject *type, PyObject *inst)
+{
+	switch (_PyObject_RealIsInstance(inst, type)) {
+	case -1:
+		return NULL;
+	case 0:
+		Py_RETURN_FALSE;
+	default:
+		Py_RETURN_TRUE;
+	}
+}
+
+
+static PyObject *
+type_get_instancecheck(PyObject *type, void *context)
+{
+	static PyMethodDef ml = {"__instancecheck__",
+				 type___instancecheck__, METH_O };
+	return PyCFunction_New(&ml, type);
+}
+
+static PyObject *
+type___subclasscheck__(PyObject *type, PyObject *inst)
+{
+	switch (_PyObject_RealIsSubclass(inst, type)) {
+	case -1:
+		return NULL;
+	case 0:
+		Py_RETURN_FALSE;
+	default:
+		Py_RETURN_TRUE;
+	}
+}
+
+static PyObject *
+type_get_subclasscheck(PyObject *type, void *context)
+{
+	static PyMethodDef ml = {"__subclasscheck__",
+				 type___subclasscheck__, METH_O };
+	return PyCFunction_New(&ml, type);
+}
+
 static PyGetSetDef type_getsets[] = {
 	{"__name__", (getter)type_name, (setter)type_set_name, NULL},
 	{"__bases__", (getter)type_get_bases, (setter)type_set_bases, NULL},
@@ -592,6 +635,8 @@ static PyGetSetDef type_getsets[] = {
 	 (setter)type_set_abstractmethods, NULL},
 	{"__dict__",  (getter)type_dict,  NULL, NULL},
 	{"__doc__", (getter)type_get_doc, NULL, NULL},
+	{"__instancecheck__", (getter)type_get_instancecheck, NULL, NULL},
+	{"__subclasscheck__", (getter)type_get_subclasscheck, NULL, NULL},
 	{0}
 };
 

Python/errors.c

@@ -160,11 +160,12 @@ PyErr_GivenExceptionMatches(PyObject *err, PyObject *exc)
 		int res = 0;
 		PyObject *exception, *value, *tb;
 		PyErr_Fetch(&exception, &value, &tb);
-		res = PyObject_IsSubclass(err, exc);
+		/* PyObject_IsSubclass() can recurse and therefore is
+		   not safe (see test_bad_getattr in test.pickletester). */
+		res = PyType_IsSubtype((PyTypeObject *)err, (PyTypeObject *)exc);
 		/* This function must not fail, so print the error here */
 		if (res == -1) {
 			PyErr_WriteUnraisable(err);
-			/* issubclass did not succeed */
 			res = 0;
 		}
 		PyErr_Restore(exception, value, tb);