From cde8b1ba0c0948f2cec00d11821214e06ca419cb Mon Sep 17 00:00:00 2001
From: Barry Warsaw <barry@python.org>
Date: Fri, 22 Aug 1997 21:14:38 +0000
Subject: Two new built-in functions: issubclass() and isinstance().  Both take
 classes as their second arguments.  The former takes a class as the first
 argument and returns true iff first is second, or is a subclass of second.

The latter takes any object as the first argument and returns true iff
first is an instance of the second, or any subclass of second.

Also, change all occurances of pointer compares against
PyExc_IndexError with PyErr_ExceptionMatches() calls.
---
 Python/bltinmodule.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 59 insertions(+), 5 deletions(-)

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 439498d..a89b3fc 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -169,7 +169,7 @@ builtin_filter(self, args)
 		if ((item = (*sqf->sq_item)(seq, i)) == NULL) {
 			if (i < len)
 				goto Fail_1;
-			if (PyErr_Occurred() == PyExc_IndexError) {
+			if (PyErr_ExceptionMatches(PyExc_IndexError)) {
 				PyErr_Clear();
 				break;
 			}
@@ -726,8 +726,9 @@ builtin_map(self, args)
 				if (item == NULL) {
 					if (i < sqp->len)
 						goto Fail_0;
-					if (PyErr_Occurred() ==
-					    PyExc_IndexError) {
+					if (PyErr_ExceptionMatches(
+						PyExc_IndexError))
+					{
 						PyErr_Clear();
 						Py_INCREF(Py_None);
 						item = Py_None;
@@ -1067,7 +1068,7 @@ min_max(args, sign)
 	for (i = 0; ; i++) {
 		x = (*sq->sq_item)(v, i); /* Implies INCREF */
 		if (x == NULL) {
-			if (PyErr_Occurred() == PyExc_IndexError) {
+			if (PyErr_ExceptionMatches(PyExc_IndexError)) {
 				PyErr_Clear();
 				break;
 			}
@@ -1415,7 +1416,7 @@ builtin_reduce(self, args)
 		}
 
 		if ((op2 = (*sqf->sq_item)(seq, i)) == NULL) {
-			if (PyErr_Occurred() == PyExc_IndexError) {
+			if (PyErr_ExceptionMatches(PyExc_IndexError)) {
 				PyErr_Clear();
 				break;
 			}
@@ -1613,6 +1614,57 @@ builtin_vars(self, args)
 	return d;
 }
 
+static PyObject *
+builtin_isinstance(self, args)
+     PyObject *self;
+     PyObject *args;
+{
+	PyObject *inst;
+	PyObject *cls;
+	int retval;
+
+	if (!PyArg_ParseTuple(args, "OO", &inst, &cls))
+		return NULL;
+	if (!PyClass_Check(cls)) {
+		PyErr_SetString(PyExc_TypeError,
+				"second argument must be a class");
+		return NULL;
+	}
+
+	if (!PyInstance_Check(inst))
+		retval = 0;
+	else {
+		PyObject *inclass =
+			(PyObject*)((PyInstanceObject*)inst)->in_class;
+		retval = PyClass_IsSubclass(inclass, cls);
+	}
+	return PyInt_FromLong(retval);
+}
+
+
+static PyObject *
+builtin_issubclass(self, args)
+     PyObject *self;
+     PyObject *args;
+{
+	PyObject *derived;
+	PyObject *cls;
+	int retval;
+
+	if (!PyArg_ParseTuple(args, "OO", &derived, &cls))
+		return NULL;
+	if (!PyClass_Check(derived) || !PyClass_Check(cls)) {
+		PyErr_SetString(PyExc_TypeError, "arguments must be classes");
+		return NULL;
+	}
+	/* shortcut */
+	if (!(retval = (derived == cls)))
+		retval = PyClass_IsSubclass(derived, cls);
+
+	return PyInt_FromLong(retval);
+}
+
+
 static PyMethodDef builtin_methods[] = {
 	{"__import__",	builtin___import__, 1},
 	{"abs",		builtin_abs, 1},
@@ -1641,6 +1693,8 @@ static PyMethodDef builtin_methods[] = {
 	{"input",	builtin_input, 1},
 	{"intern",	builtin_intern, 1},
 	{"int",		builtin_int, 1},
+	{"isinstance",  builtin_isinstance, 1},
+	{"issubclass",  builtin_issubclass, 1},
 	{"len",		builtin_len, 1},
 	{"list",	builtin_list, 1},
 	{"locals",	builtin_locals, 1},
-- 
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