diff --git a/Objects/abstract.c b/Objects/abstract.c
index 4e5838f..7016c2e 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -980,6 +980,8 @@
 int
 PySequence_Check(PyObject *s)
 {
+	if (PyObject_IsInstance(s, (PyObject *)&PyDict_Type))
+		return 0;
 	return s != NULL && s->ob_type->tp_as_sequence &&
 		s->ob_type->tp_as_sequence->sq_item != NULL;
 }
diff --git a/Objects/dictnotes.txt b/Objects/dictnotes.txt
index 3b63197..d3aa774 100644
--- a/Objects/dictnotes.txt
+++ b/Objects/dictnotes.txt
@@ -98,6 +98,17 @@
     depending on the size of the dictionary.  Setting to *4
     eliminates every other resize step.
 
+* Maximum sparseness (minimum dictionary load).  What percentage
+    of entries can be unused before the dictionary shrinks to
+    free up memory and speed up iteration?  (The current CPython
+    code does not represent this parameter directly.)
+
+* Shrinkage rate upon exceeding maximum sparseness.  The current
+    CPython code never even checks sparseness when deleting a
+    key.  When a new key is added, it resizes based on the number
+    of active keys, so that the addition may trigger shrinkage
+    rather than growth.
+
 Tune-ups should be measured across a broad range of applications and
 use cases.  A change to any parameter will help in some situations and
 hurt in others.  The key is to find settings that help the most common
@@ -115,6 +126,15 @@
 Also, every dictionary iterates at least twice, once for the memset()
 when it is created and once by dealloc().
 
+Dictionary operations involving only a single key can be O(1) unless 
+resizing is possible.  By checking for a resize only when the 
+dictionary can grow (and may *require* resizing), other operations
+remain O(1), and the odds of resize thrashing or memory fragmentation
+are reduced. In particular, an algorithm that empties a dictionary
+by repeatedly invoking .pop will see no resizing, which might
+not be necessary at all because the dictionary is eventually
+discarded entirely.
+
 
 Results of Cache Locality Experiments
 -------------------------------------
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index eeb8bd5..ffa7a86 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -833,6 +833,34 @@
 	return 1;
 }
 
+/* Internal version of PyDict_Next that returns a hash value in addition to the key and value.*/
+int
+_PyDict_Next(PyObject *op, Py_ssize_t *ppos, PyObject **pkey, PyObject **pvalue, long *phash)
+{
+	register Py_ssize_t i;
+	register Py_ssize_t mask;
+	register dictentry *ep;
+
+	if (!PyDict_Check(op))
+		return 0;
+	i = *ppos;
+	if (i < 0)
+		return 0;
+	ep = ((dictobject *)op)->ma_table;
+	mask = ((dictobject *)op)->ma_mask;
+	while (i <= mask && ep[i].me_value == NULL)
+		i++;
+	*ppos = i+1;
+	if (i > mask)
+		return 0;
+        *phash = (long)(ep[i].me_hash);
+	if (pkey)
+		*pkey = ep[i].me_key;
+	if (pvalue)
+		*pvalue = ep[i].me_value;
+	return 1;
+}
+
 /* Methods */
 
 static void
@@ -1336,7 +1364,7 @@
 		return -1;
 	}
 	mp = (dictobject*)a;
-	if (PyDict_Check(b)) {
+	if (PyDict_CheckExact(b)) {
 		other = (dictobject*)b;
 		if (other == mp || other->ma_used == 0)
 			/* a.update(a) or a.update({}); nothing to do */
@@ -1909,6 +1937,17 @@
 	return ep == NULL ? -1 : (ep->me_value != NULL);
 }
 
+/* Internal version of PyDict_Contains used when the hash value is already known */
+int
+_PyDict_Contains(PyObject *op, PyObject *key, long hash)
+{
+	dictobject *mp = (dictobject *)op;
+	dictentry *ep;
+
+	ep = (mp->ma_lookup)(mp, key, hash);
+	return ep == NULL ? -1 : (ep->me_value != NULL);
+}
+
 /* Hack to implement "key in dict" */
 static PySequenceMethods dict_as_sequence = {
 	0,			/* sq_length */
diff --git a/Objects/enumobject.c b/Objects/enumobject.c
index a8f43e0..a456c9d 100644
--- a/Objects/enumobject.c
+++ b/Objects/enumobject.c
@@ -62,6 +62,12 @@
 	PyObject *result = en->en_result;
 	PyObject *it = en->en_sit;
 
+	if (en->en_index == LONG_MAX) {
+		PyErr_SetString(PyExc_OverflowError,
+			"enumerate() is limited to LONG_MAX items");                
+		return NULL;         
+	}
+
 	next_item = (*it->ob_type->tp_iternext)(it);
 	if (next_item == NULL)
 		return NULL;
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 0f6c902..2210edf 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -932,14 +932,31 @@
 {
 	PyObject *key, *it;
 
-	if (PyAnySet_Check(other))
+	if (PyAnySet_CheckExact(other))
 		return set_merge(so, other);
 
 	if (PyDict_CheckExact(other)) {
 		PyObject *value;
 		Py_ssize_t pos = 0;
-		while (PyDict_Next(other, &pos, &key, &value)) {
-			if (set_add_key(so, key) == -1)
+		long hash;
+		Py_ssize_t dictsize = PyDict_Size(other);
+
+		/* Do one big resize at the start, rather than
+		* incrementally resizing as we insert new keys.  Expect
+		* that there will be no (or few) overlapping keys.
+		*/
+		if (dictsize == -1)
+			return -1;
+		if ((so->fill + dictsize)*3 >= (so->mask+1)*2) {
+			if (set_table_resize(so, (so->used + dictsize)*2) != 0)
+				return -1;
+		}
+		while (_PyDict_Next(other, &pos, &key, &value, &hash)) {
+			setentry an_entry;
+
+			an_entry.hash = hash;
+			an_entry.key = key;
+			if (set_add_entry(so, &an_entry) == -1)
 				return -1;
 		}
 		return 0;
@@ -1210,7 +1227,7 @@
 	if (result == NULL)
 		return NULL;
 
-	if (PyAnySet_Check(other)) {		
+	if (PyAnySet_CheckExact(other)) {		
 		Py_ssize_t pos = 0;
 		setentry *entry;
 
@@ -1334,7 +1351,7 @@
 	if ((PyObject *)so == other)
 		return set_clear_internal(so);
 	
-	if (PyAnySet_Check(other)) {
+	if (PyAnySet_CheckExact(other)) {
 		setentry *entry;
 		Py_ssize_t pos = 0;
 
@@ -1383,7 +1400,7 @@
 	setentry *entry;
 	Py_ssize_t pos = 0;
 
-	if (!PyAnySet_Check(other)  && !PyDict_CheckExact(other)) {
+	if (!PyAnySet_CheckExact(other)  && !PyDict_CheckExact(other)) {
 		result = set_copy(so);
 		if (result == NULL)
 			return NULL;
@@ -1402,7 +1419,7 @@
 			setentry entrycopy;
 			entrycopy.hash = entry->hash;
 			entrycopy.key = entry->key;
-			if (!PyDict_Contains(other, entry->key)) {
+			if (!_PyDict_Contains(other, entry->key, entry->hash)) {
 				if (set_add_entry((PySetObject *)result, &entrycopy) == -1) {
 					Py_DECREF(result);
 					return NULL;
@@ -1473,12 +1490,10 @@
 	if (PyDict_CheckExact(other)) {
 		PyObject *value;
 		int rv;
-		while (PyDict_Next(other, &pos, &key, &value)) {
+		long hash;
+		while (_PyDict_Next(other, &pos, &key, &value, &hash)) {
 			setentry an_entry;
-			long hash = PyObject_Hash(key);
 
-			if (hash == -1)
-				return NULL;
 			an_entry.hash = hash;
 			an_entry.key = key;
 			rv = set_discard_entry(so, &an_entry);
@@ -1492,7 +1507,7 @@
 		Py_RETURN_NONE;
 	}
 
-	if (PyAnySet_Check(other)) {
+	if (PyAnySet_CheckExact(other)) {
 		Py_INCREF(other);
 		otherset = (PySetObject *)other;
 	} else {
@@ -1575,7 +1590,7 @@
 	setentry *entry;
 	Py_ssize_t pos = 0;
 
-	if (!PyAnySet_Check(other)) {
+	if (!PyAnySet_CheckExact(other)) {
 		PyObject *tmp, *result;
 		tmp = make_new_set(&PySet_Type, other);
 		if (tmp == NULL)
@@ -1604,7 +1619,7 @@
 {
 	PyObject *tmp, *result;
 
-	if (!PyAnySet_Check(other)) {
+	if (!PyAnySet_CheckExact(other)) {
 		tmp = make_new_set(&PySet_Type, other);
 		if (tmp == NULL)
 			return NULL;
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index cd211e6..848203e 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -4279,7 +4279,13 @@
 SLOT1(slot_nb_inplace_subtract, "__isub__", PyObject *, "O")
 SLOT1(slot_nb_inplace_multiply, "__imul__", PyObject *, "O")
 SLOT1(slot_nb_inplace_remainder, "__imod__", PyObject *, "O")
-SLOT1(slot_nb_inplace_power, "__ipow__", PyObject *, "O")
+/* Can't use SLOT1 here, because nb_inplace_power is ternary */
+static PyObject * 
+slot_nb_inplace_power(PyObject *self, PyObject * arg1, PyObject *arg2) 
+{ 
+  static PyObject *cache_str; 
+  return call_method(self, "__ipow__", &cache_str, "(" "O" ")", arg1); 
+}
 SLOT1(slot_nb_inplace_lshift, "__ilshift__", PyObject *, "O")
 SLOT1(slot_nb_inplace_rshift, "__irshift__", PyObject *, "O")
 SLOT1(slot_nb_inplace_and, "__iand__", PyObject *, "O")