Index: Lib/test/test_mmap.py
===================================================================
--- Lib/test/test_mmap.py	(revision 53047)
+++ Lib/test/test_mmap.py	(working copy)
@@ -306,6 +306,40 @@
             m[x] = ch = chr(x & 255)
             self.assertEqual(m[x], ch)
 
+    def test_extended_getslice(self):
+        # Test extended slicing by comparing with list slicing.
+        s = "".join(chr(c) for c in reversed(range(256)))
+        m = mmap.mmap(-1, len(s))
+        m[:] = s
+        self.assertEqual(m[:], s)
+        indices = (0, None, 1, 3, 19, 300, -1, -2, -31, -300)
+        for start in indices:
+            for stop in indices:
+                # Skip step 0 (invalid)
+                for step in indices[1:]:
+                    self.assertEqual(m[start:stop:step],
+                                     s[start:stop:step])
+
+    def test_extended_set_del_slice(self):
+        # Test extended slicing by comparing with list slicing.
+        s = "".join(chr(c) for c in reversed(range(256)))
+        m = mmap.mmap(-1, len(s))
+        indices = (0, None, 1, 3, 19, 300, -1, -2, -31, -300)
+        for start in indices:
+            for stop in indices:
+                # Skip invalid step 0
+                for step in indices[1:]:
+                    m[:] = s
+                    self.assertEqual(m[:], s)
+                    L = list(s)
+                    # Make sure we have a slice of exactly the right length,
+                    # but with different data.
+                    data = L[start:stop:step]
+                    data = "".join(reversed(data))
+                    L[start:stop:step] = data
+                    m[start:stop:step] = data
+                    self.assertEquals(m[:], "".join(L))
+
 def test_main():
     run_unittest(MmapTests)
 
Index: Modules/mmapmodule.c
===================================================================
--- Modules/mmapmodule.c	(revision 53047)
+++ Modules/mmapmodule.c	(working copy)
@@ -681,6 +681,60 @@
 }
 
 static PyObject *
+mmap_subscript(mmap_object *self, PyObject *item)
+{
+	CHECK_VALID(NULL);
+	if (PyIndex_Check(item)) {
+		Py_ssize_t i = PyNumber_AsSsize_t(item, PyExc_IndexError);
+		if (i == -1 && PyErr_Occurred())
+			return NULL;
+		if (i < 0)
+			i += self->size;
+		if (i < 0 || i > self->size) {
+			PyErr_SetString(PyExc_IndexError,
+				"mmap index out of range");
+			return NULL;
+		}
+		return PyString_FromStringAndSize(self->data + i, 1);
+	}
+	else if (PySlice_Check(item)) {
+		Py_ssize_t start, stop, step, slicelen;
+
+		if (PySlice_GetIndicesEx((PySliceObject *)item, self->size,
+				 &start, &stop, &step, &slicelen) < 0) {
+			return NULL;
+		}
+		
+		if (slicelen <= 0)
+			return PyString_FromStringAndSize("", 0);
+		else if (step == 1)
+			return PyString_FromStringAndSize(self->data + start,
+							  slicelen);
+		else {
+			char *result_buf = (char *)PyMem_Malloc(slicelen);
+			Py_ssize_t cur, i;
+			PyObject *result;
+
+			if (result_buf == NULL)
+				return PyErr_NoMemory();
+			for (cur = start, i = 0; i < slicelen;
+			     cur += step, i++) {
+			     	result_buf[i] = self->data[cur];
+			}
+			result = PyString_FromStringAndSize(result_buf,
+							    slicelen);
+			PyMem_Free(result_buf);
+			return result;
+		}
+	}
+	else {
+		PyErr_SetString(PyExc_TypeError,
+				"mmap indices must be integers");
+		return NULL;
+	}
+}
+
+static PyObject *
 mmap_concat(mmap_object *self, PyObject *bb)
 {
 	CHECK_VALID(NULL);
@@ -764,6 +818,96 @@
 	return 0;
 }
 
+static int
+mmap_ass_subscript(mmap_object *self, PyObject *item, PyObject *value)
+{
+	CHECK_VALID(-1);
+
+	if (PyIndex_Check(item)) {
+		Py_ssize_t i = PyNumber_AsSsize_t(item, PyExc_IndexError);
+		const char *buf;
+
+		if (i == -1 && PyErr_Occurred())
+			return -1;
+		if (i < 0)
+			i += self->size;
+		if (i < 0 || i > self->size) {
+			PyErr_SetString(PyExc_IndexError,
+				"mmap index out of range");
+			return -1;
+		}
+		if (value == NULL) {
+			PyErr_SetString(PyExc_TypeError,
+				"mmap object doesn't support item deletion");
+			return -1;
+		}
+		if (!PyString_Check(value) || PyString_Size(value) != 1) {
+			PyErr_SetString(PyExc_IndexError,
+		          "mmap assignment must be single-character string");
+			return -1;
+		}
+		if (!is_writeable(self))
+			return -1;
+		buf = PyString_AsString(value);
+		self->data[i] = buf[0];
+		return 0;
+	}
+	else if (PySlice_Check(item)) {
+		Py_ssize_t start, stop, step, slicelen;
+		
+		if (PySlice_GetIndicesEx((PySliceObject *)item,
+					 self->size, &start, &stop,
+					 &step, &slicelen) < 0) {
+			return -1;
+		}
+		if (value == NULL) {
+			PyErr_SetString(PyExc_TypeError,
+				"mmap object doesn't support slice deletion");
+			return -1;
+		}
+		if (!PyString_Check(value)) {
+			PyErr_SetString(PyExc_IndexError,
+				"mmap slice assignment must be a string");
+			return -1;
+		}
+		if (PyString_Size(value) != slicelen) {
+			PyErr_SetString(PyExc_IndexError,
+				"mmap slice assignment is wrong size");
+			return -1;
+		}
+		if (!is_writeable(self))
+			return -1;
+
+		if (slicelen == 0)
+			return 0;
+		else if (step == 1) {
+			const char *buf = PyString_AsString(value);
+
+			if (buf == NULL)
+				return -1;
+			memcpy(self->data + start, buf, slicelen);
+			return 0;
+		}
+		else {
+			Py_ssize_t cur, i;
+			const char *buf = PyString_AsString(value);
+			
+			if (buf == NULL)
+				return -1;
+			for (cur = start, i = 0; i < slicelen;
+			     cur += step, i++) {
+				self->data[cur] = buf[i];
+			}
+			return 0;
+		}
+	}
+	else {
+		PyErr_SetString(PyExc_TypeError,
+				"mmap indices must be integer");
+		return -1;
+	}
+}
+
 static PySequenceMethods mmap_as_sequence = {
 	(lenfunc)mmap_length,		       /*sq_length*/
 	(binaryfunc)mmap_concat,	       /*sq_concat*/
@@ -774,6 +918,12 @@
 	(ssizessizeobjargproc)mmap_ass_slice,      /*sq_ass_slice*/
 };
 
+static PyMappingMethods mmap_as_mapping = {
+	(lenfunc)mmap_length,
+	(binaryfunc)mmap_subscript,
+	(objobjargproc)mmap_ass_subscript,
+};
+
 static PyBufferProcs mmap_as_buffer = {
 	(readbufferproc)mmap_buffer_getreadbuf,
 	(writebufferproc)mmap_buffer_getwritebuf,
@@ -796,7 +946,7 @@
 	0,					/* tp_repr */
 	0,					/* tp_as_number */
 	&mmap_as_sequence,			/*tp_as_sequence*/
-	0,					/*tp_as_mapping*/
+	&mmap_as_mapping,			/*tp_as_mapping*/
 	0,					/*tp_hash*/
 	0,					/*tp_call*/
 	0,					/*tp_str*/