#2719: backport next() from 3k.

Doc/library/functions.rst

@@ -710,6 +710,15 @@ available.  They are listed here in alphabetical order.
       Added support for the optional *key* argument.
 
 
+.. function:: next(iterator[, default])
+
+   Retrieve the next item from the *iterator* by calling its :meth:`next`
+   method.  If *default* is given, it is returned if the iterator is exhausted,
+   otherwise :exc:`StopIteration` is raised.
+
+   .. versionadded:: 2.6
+
+
 .. function:: object()
 
    Return a new featureless object.  :class:`object` is a base for all new style

Lib/test/test_builtin.py

@@ -1539,6 +1539,33 @@ class BuiltinTest(unittest.TestCase):
         self.assertEqual(min(data, key=f),
                          sorted(data, key=f)[0])
 
+    def test_next(self):
+        it = iter(range(2))
+        self.assertEqual(next(it), 0)
+        self.assertEqual(next(it), 1)
+        self.assertRaises(StopIteration, next, it)
+        self.assertRaises(StopIteration, next, it)
+        self.assertEquals(next(it, 42), 42)
+
+        class Iter(object):
+            def __iter__(self):
+                return self
+            def next(self):
+                raise StopIteration
+
+        it = iter(Iter())
+        self.assertEquals(next(it, 42), 42)
+        self.assertRaises(StopIteration, next, it)
+
+        def gen():
+            yield 1
+            return
+
+        it = gen()
+        self.assertEquals(next(it), 1)
+        self.assertRaises(StopIteration, next, it)
+        self.assertEquals(next(it, 42), 42)
+
     def test_oct(self):
         self.assertEqual(oct(100), '0144')
         self.assertEqual(oct(100L), '0144L')

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 2.6 alpha 3?
 Core and builtins
 -----------------
 
+- Issue #2719: backported the ``next()`` builtin from Python 3.
+
 - Issue #2681: The octal literal ``0o8`` was incorrecly acctepted. Now it
   properly raises a SyntaxError.
 

Python/bltinmodule.c

@@ -1070,6 +1070,47 @@ sequences have the same length.  If the function is None, return a list of\n\
 the items of the sequence (or a list of tuples if more than one sequence).");
 
 
+static PyObject *
+builtin_next(PyObject *self, PyObject *args)
+{
+	PyObject *it, *res;
+	PyObject *def = NULL;
+
+	if (!PyArg_UnpackTuple(args, "next", 1, 2, &it, &def))
+		return NULL;
+	if (!PyIter_Check(it)) {
+		PyErr_Format(PyExc_TypeError,
+			"%.200s object is not an iterator",
+			it->ob_type->tp_name);
+		return NULL;
+	}
+	
+	res = (*it->ob_type->tp_iternext)(it);
+	if (res != NULL) {
+		return res;
+	} else if (def != NULL) {
+		if (PyErr_Occurred()) {
+			if (!PyErr_ExceptionMatches(PyExc_StopIteration))
+				return NULL;
+			PyErr_Clear();
+		}
+		Py_INCREF(def);
+		return def;
+	} else if (PyErr_Occurred()) {
+		return NULL;
+	} else {
+		PyErr_SetNone(PyExc_StopIteration);
+		return NULL;
+	}
+}
+
+PyDoc_STRVAR(next_doc,
+"next(iterator[, default])\n\
+\n\
+Return the next item from the iterator. If default is given and the iterator\n\
+is exhausted, it is returned instead of raising StopIteration.");
+
+
 static PyObject *
 builtin_setattr(PyObject *self, PyObject *args)
 {
@@ -2509,6 +2550,7 @@ static PyMethodDef builtin_methods[] = {
  	{"map",		builtin_map,        METH_VARARGS, map_doc},
  	{"max",		(PyCFunction)builtin_max,        METH_VARARGS | METH_KEYWORDS, max_doc},
  	{"min",		(PyCFunction)builtin_min,        METH_VARARGS | METH_KEYWORDS, min_doc},
+	{"next", 	builtin_next,       METH_VARARGS, next_doc},
  	{"oct",		builtin_oct,        METH_O, oct_doc},
  	{"open",	(PyCFunction)builtin_open,       METH_VARARGS | METH_KEYWORDS, open_doc},
  	{"ord",		builtin_ord,        METH_O, ord_doc},