create copy using list(values)

Author: KittenHero

Lib/_collections_abc.py

@@ -7,7 +7,6 @@
 """
 
 from abc import ABCMeta, abstractmethod
-from itertools import islice
 import sys
 
 __all__ = ["Awaitable", "Coroutine",
@@ -988,7 +987,7 @@ def reverse(self):
     def extend(self, values):
         'S.extend(iterable) -- extend sequence by appending elements from the iterable'
         if values is self:
-            values = islice(self, len(self))
+            values = list(values)
         for v in values:
             self.append(v)