Issue #21321: itertools.islice() now releases the reference to the source iterator when the slice is exhausted.
Patch by Anton Afanasyev.
diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index 7233e7c..291aeb0 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -1,7 +1,7 @@
import unittest
from test import test_support
from itertools import *
-from weakref import proxy
+import weakref
from decimal import Decimal
from fractions import Fraction
import sys
@@ -792,6 +792,15 @@
self.assertEqual(list(islice(c, 1, 3, 50)), [1])
self.assertEqual(next(c), 3)
+ # Issue #21321: check source iterator is not referenced
+ # from islice() after the latter has been exhausted
+ it = (x for x in (1, 2))
+ wr = weakref.ref(it)
+ it = islice(it, 1)
+ self.assertIsNotNone(wr())
+ list(it) # exhaust the iterator
+ self.assertIsNone(wr())
+
def test_takewhile(self):
data = [1, 3, 5, 20, 2, 4, 6, 8]
underten = lambda x: x<10
@@ -901,7 +910,7 @@
# test that tee objects are weak referencable
a, b = tee(xrange(10))
- p = proxy(a)
+ p = weakref.proxy(a)
self.assertEqual(getattr(p, '__class__'), type(b))
del a
self.assertRaises(ReferenceError, getattr, p, '__class__')