Index: Python/compile.c
===================================================================
--- Python/compile.c	(revision 46597)
+++ Python/compile.c	(working copy)
@@ -609,6 +609,30 @@
 	return 1;
 }
 
+/* Try to convert "x in (5, 6, 7)" and "x in [5, 6, 7]"
+    into "x in set([5, 6, 7])" */
+static int
+optimize_in_const_seq(unsigned char *codestr, int lc_inst, PyObject *consts)
+{
+    PyObject *opt_set, *tuple;
+    int new_index;
+    
+    tuple = PyList_GET_ITEM(consts, GETARG(codestr, lc_inst));
+    if (NULL == tuple)
+        return 1;
+
+    opt_set = PyFrozenSet_New(tuple);
+    if (NULL == opt_set)
+        return 1;
+    new_index = PyList_GET_SIZE(consts);
+    if(PyList_Append(consts, opt_set)) {
+        Py_DECREF(opt_set);
+        return 1;
+    }
+    SETARG(codestr, lc_inst, new_index);
+    return 0;
+}
+
 static unsigned int *
 markblocks(unsigned char *code, int len)
 {
@@ -752,10 +776,22 @@
 				if (j < 6  ||  j > 9  ||
 				    codestr[i+3] != UNARY_NOT  || 
 				    !ISBASICBLOCK(blocks,i,4))
-					continue;
+					goto cmp_op_in_set;
 				SETARG(codestr, i, (j^1));
 				codestr[i+3] = NOP;
-				break;
+                
+                /* Try to convert "x in (5, 6, 7)" and "x in [5, 6, 7]"
+                into "x in set([5, 6, 7])" */
+				
+                cmp_op_in_set:
+                j = GETARG(codestr, i);
+                tgt = GETARG(codestr, i-3);
+                if (j < 6 || j > 9 ||
+                    codestr[i-3] != LOAD_CONST ||
+                    !PyTuple_CheckExact(PyList_GET_ITEM(consts, tgt)) ||
+                    optimize_in_const_seq(codestr, i-3, consts))
+                    continue;
+                break;
 
 				/* Replace LOAD_GLOBAL/LOAD_NAME None
                                    with LOAD_CONST None */
Index: Lib/test/test_peepholer.py
===================================================================
--- Lib/test/test_peepholer.py	(revision 46597)
+++ Lib/test/test_peepholer.py	(working copy)
@@ -160,6 +160,29 @@
         self.assert_('LOAD_CONST' not in asm)
         self.assert_('(None)' not in asm)
         self.assertEqual(asm.split().count('RETURN_VALUE'), 1)
+        
+    def test_convert_in_tuple_to_frozenset(self):
+        # convert "x in (5, 6, 7):" to "x in frozenset([5, 6, 7])"
+        
+        def f(x):
+            if x in (5, 6, 7):
+                pass
+                
+        asm = disassemble(f)
+        self.assert_('((5, 6, 7))' not in asm)
+        self.assert_('(frozenset([5, 6, 7]))' in asm)
+        
+    def test_convert_in_list_to_frozenset(self):
+        # convert "x in [5, 6, 7]:" to "x in frozenset([5, 6, 7])"
+        
+        def f(x):
+            if x in [5, 6, 7]:
+                pass
+                
+        asm = disassemble(f)
+        # The [5, 6, 7] gets optimised to (5, 6, 7) by a different optimiser
+        self.assert_('((5, 6, 7))' not in asm)
+        self.assert_('(frozenset([5, 6, 7]))' in asm)