From 0ed3891915425b1af26e26c4c5d350e85e7ea4cf Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 30 Mar 2016 21:02:00 +0300
Subject: [PATCH] Issue #26492: Added additional tests for exhausted iterators
 of mutable sequences.

---
 Lib/test/list_tests.py | 11 +++++++++++
 Lib/test/test_bytes.py | 10 ++++++++++
 Lib/test/test_iter.py  | 11 +++++++++++
 3 files changed, 32 insertions(+)

diff --git a/Lib/test/list_tests.py b/Lib/test/list_tests.py
index b8d6d6bda67..ed606db0d11 100644
--- a/Lib/test/list_tests.py
+++ b/Lib/test/list_tests.py
@@ -532,3 +532,14 @@ class CommonTest(seq_tests.CommonTest):
             def __iter__(self):
                 raise KeyboardInterrupt
         self.assertRaises(KeyboardInterrupt, list, F())
+
+    def test_exhausted_iterator(self):
+        a = self.type2test([1, 2, 3])
+        exhit = iter(a)
+        empit = iter(a)
+        for x in exhit:  # exhaust the iterator
+            next(empit)  # not exhausted
+        a.append(9)
+        self.assertEqual(list(exhit), [])
+        self.assertEqual(list(empit), [9])
+        self.assertEqual(a, self.type2test([1, 2, 3, 9]))
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 82ad451db01..bdcb88ac6ed 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -900,6 +900,16 @@ class ByteArrayTest(BaseBytesTest):
         # PyByteArray_AS_STRING() C macro.
         self.assertRaises(ValueError, int, bytearray(b''))
 
+    def test_exhausted_iterator(self):
+        a = self.type2test([1, 2, 3])
+        exhit = iter(a)
+        empit = iter(a)
+        for x in exhit:  # exhaust the iterator
+            next(empit)  # not exhausted
+        a.append(9)
+        self.assertEqual(list(exhit), [])
+        self.assertEqual(list(empit), [9])
+        self.assertEqual(a, self.type2test([1, 2, 3, 9]))
 
 class AssortedBytesTest(unittest.TestCase):
     #
diff --git a/Lib/test/test_iter.py b/Lib/test/test_iter.py
index 4495fa1ad72..cc20865df18 100644
--- a/Lib/test/test_iter.py
+++ b/Lib/test/test_iter.py
@@ -122,6 +122,17 @@ class TestCase(unittest.TestCase):
     def test_seq_class_iter(self):
         self.check_iterator(iter(SequenceClass(10)), range(10))
 
+    def test_mutating_seq_class_exhausted_iter(self):
+        a = SequenceClass(5)
+        exhit = iter(a)
+        empit = iter(a)
+        for x in exhit:  # exhaust the iterator
+            next(empit)  # not exhausted
+        a.n = 7
+        self.assertEqual(list(exhit), [])
+        self.assertEqual(list(empit), [5, 6])
+        self.assertEqual(list(a), [0, 1, 2, 3, 4, 5, 6])
+
     # Test a new_style class with __iter__ but no next() method
     def test_new_style_iter_class(self):
         class IterClass(object):