Teach the UNPACK_SEQUENCE opcode how to tease an iterable object into

giving up the goods.
NEEDS DOC CHANGES

Lib/test/test_iter.py

@@ -594,4 +594,57 @@ class TestCase(unittest.TestCase):
             except OSError:
                 pass
 
+    # Test iterators on RHS of unpacking assignments.
+    def test_unpack_iter(self):
+        a, b = 1, 2
+        self.assertEqual((a, b), (1, 2))
+
+        a, b, c = IteratingSequenceClass(3)
+        self.assertEqual((a, b, c), (0, 1, 2))
+
+        try:    # too many values
+            a, b = IteratingSequenceClass(3)
+        except ValueError:
+            pass
+        else:
+            self.fail("should have raised ValueError")
+
+        try:    # not enough values
+            a, b, c = IteratingSequenceClass(2)
+        except ValueError:
+            pass
+        else:
+            self.fail("should have raised ValueError")
+
+        try:    # not iterable
+            a, b, c = len
+        except TypeError:
+            pass
+        else:
+            self.fail("should have raised TypeError")
+
+        a, b, c = {1: 42, 2: 42, 3: 42}.itervalues()
+        self.assertEqual((a, b, c), (42, 42, 42))
+
+        f = open(TESTFN, "w")
+        lines = ("a\n", "bb\n", "ccc\n")
+        try:
+            for line in lines:
+                f.write(line)
+        finally:
+            f.close()
+        f = open(TESTFN, "r")
+        try:
+            a, b, c = f
+            self.assertEqual((a, b, c), lines)
+        finally:
+            f.close()
+            try:
+                unlink(TESTFN)
+            except OSError:
+                pass
+
+        (a, b), (c,) = IteratingSequenceClass(2), {42: 24}
+        self.assertEqual((a, b, c), (0, 1, 42))
+
 run_unittest(TestCase)