#8401: assigning an int to a bytearray slice (e.g. b[3:4] = 5) now raises an error.

Lib/test/test_bytes.py

@@ -635,6 +635,26 @@ class ByteArrayTest(BaseBytesTest):
         b[3:0] = [42, 42, 42]
         self.assertEqual(b, bytearray([0, 1, 2, 42, 42, 42, 3, 4, 5, 6, 7, 8, 9]))
 
+        b[3:] = b'foo'
+        self.assertEqual(b, bytearray([0, 1, 2, 102, 111, 111]))
+
+        b[:3] = memoryview(b'foo')
+        self.assertEqual(b, bytearray([102, 111, 111, 102, 111, 111]))
+
+        b[3:4] = []
+        self.assertEqual(b, bytearray([102, 111, 111, 111, 111]))
+
+        b[1:] = list(b'uuuu')  # this works only on Python2
+        self.assertEqual(b, bytearray([102, 117, 117, 117, 117]))
+
+        for elem in [5, -5, 0, long(10e20), u'str', 2.3, [u'a', u'b'], [[]]]:
+            with self.assertRaises(TypeError):
+                b[3:4] = elem
+
+        for elem in [[254, 255, 256], [-256, 9000]]:
+            with self.assertRaises(ValueError):
+                b[3:4] = elem
+
     def test_extended_set_del_slice(self):
         indices = (0, None, 1, 3, 19, 300, 1<<333, -1, -2, -31, -300)
         for start in indices:

Misc/NEWS

@@ -9,6 +9,9 @@ What's New in Python 2.7.4
 Core and Builtins
 -----------------
 
+- Issue #8401: assigning an int to a bytearray slice (e.g. b[3:4] = 5) now
+  raises an error.
+
 - Issue #14700: Fix buggy overflow checks for large width and precision
   in string formatting operations.
 

Objects/bytearrayobject.c

@@ -636,6 +636,12 @@ bytearray_ass_subscript(PyByteArrayObject *self, PyObject *index, PyObject *valu
         needed = 0;
     }
     else if (values == (PyObject *)self || !PyByteArray_Check(values)) {
+        if (PyNumber_Check(values) || PyUnicode_Check(values)) {
+            PyErr_SetString(PyExc_TypeError,
+                            "can assign only bytes, buffers, or iterables "
+                            "of ints in range(0, 256)");
+            return -1;
+        }
         /* Make a copy and call this function recursively */
         int err;
         values = PyByteArray_FromObject(values);