From: Raymond Hettinger <python@rcn.com>
Date: Wed, 7 May 2003 01:28:47 +0000 (+0000)
Subject: SF bug #730296: Unexpected Changes in list Iterator
X-Git-Tag: v2.3c1~821
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=686b14d7ad700cfb3d3f0538695f0aa8e6c1b0b8;p=python

SF bug #730296: Unexpected Changes in list Iterator

Reverted a Py2.3b1 change to iterator in subclasses of list and tuple.
They had been changed to use __getitem__ whenever it had been overriden
in the subclass.

This caused some usabilty and performance problems.  Also, it was
inconsistent with the rest of python where many container methods
access the underlying object directly without first checking for
an overridden getter.  Users needing a change in iterator behavior
should override it directly.
---

diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
index 7e238df3e0..1532295708 100644
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -256,11 +256,11 @@ def f():
         yield i
 vereq(list(tuple(f())), range(1000))
 
-# Verify that __getitem__ overrides are recognized by __iter__
+# Verify that __getitem__ overrides are not recognized by __iter__
 class T(tuple):
   def __getitem__(self, key):
      return str(key) + '!!!'
-vereq(iter(T()).next(), '0!!!')
+vereq(iter(T((1,2))).next(), 1)
 
 print '6.5.3 Lists'
 # calling built-in types without argument must return empty
@@ -453,11 +453,11 @@ a = range(10)
 a[::2] = tuple(range(5))
 vereq(a, [0, 1, 1, 3, 2, 5, 3, 7, 4, 9])
 
-# Verify that __getitem__ overrides are recognized by __iter__
+# Verify that __getitem__ overrides are not recognized by __iter__
 class L(list):
   def __getitem__(self, key):
      return str(key) + '!!!'
-vereq(iter(L()).next(), '0!!!')
+vereq(iter(L([1,2])).next(), 1)
 
 
 print '6.6 Mappings == Dictionaries'
diff --git a/Misc/NEWS b/Misc/NEWS
index 9f982dbfbb..98feacc8a1 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -15,6 +15,11 @@ Core and builtins
 - The softspace attribute of file objects became read-only by oversight.
   It's writable again.
 
+- Reverted a 2.3 beta 1 change to iterators for subclasses of list and
+  tuple.  By default, the iterators now access data elements directly
+  instead of going through __getitem__.  If __getitem__ access is
+  preferred, then __iter__ can be overriden.
+
 Extension modules
 -----------------
 
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 36bbe22179..48f3d7d6ea 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2382,8 +2382,6 @@ list_iter(PyObject *seq)
 		PyErr_BadInternalCall();
 		return NULL;
 	}
-	if (seq->ob_type->tp_as_sequence->sq_item != (intargfunc)list_item)
-		return PySeqIter_New(seq);
 	it = PyObject_GC_New(listiterobject, &PyListIter_Type);
 	if (it == NULL)
 		return NULL;
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 7456533ccd..282da3e8b9 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -753,8 +753,6 @@ tuple_iter(PyObject *seq)
 		PyErr_BadInternalCall();
 		return NULL;
 	}
-	if (seq->ob_type->tp_as_sequence->sq_item != (intargfunc)tupleitem)
-		return PySeqIter_New(seq);
 	it = PyObject_GC_New(tupleiterobject, &PyTupleIter_Type);
 	if (it == NULL)
 		return NULL;