- New builtin function enumerate(x), from PEP 279. Example:

enumerate("abc") is an iterator returning (0,"a"), (1,"b"), (2,"c").
  The argument can be an arbitrary iterable object.

Objects/enumobject.c

@@ -0,0 +1,139 @@
+/* enumerate object */
+
+#include "Python.h"
+
+typedef struct {
+	PyObject_HEAD
+	long      en_index;        /* current index of enumeration */
+	PyObject* en_sit;          /* secondary iterator of enumeration */
+} enumobject;
+
+PyTypeObject PyEnum_Type;
+
+static PyObject *
+enum_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+	enumobject *en;
+	PyObject *seq = NULL;
+	static char *kwlist[] = {"sequence", 0};
+
+	if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:enumerate", kwlist,
+					 &seq))
+		return NULL;
+
+	en = (enumobject *)type->tp_alloc(type, 0);
+	if (en == NULL)
+		return NULL;
+	en->en_index = 0;
+	en->en_sit = PyObject_GetIter(seq);
+	if (en->en_sit == NULL) {
+		Py_DECREF(en);
+		return NULL;
+	}
+	return (PyObject *)en;
+}
+
+static void
+enum_dealloc(enumobject *en)
+{
+	PyObject_GC_UnTrack(en);
+	Py_XDECREF(en->en_sit);
+	en->ob_type->tp_free(en);
+}
+
+static int
+enum_traverse(enumobject *en, visitproc visit, void *arg)
+{
+	if (en->en_sit)
+		return visit(en->en_sit, arg);
+	return 0;
+}
+
+static PyObject *
+enum_next(enumobject *en)
+{
+	PyObject *result;
+	PyObject *next_index;
+
+	PyObject *next_item = PyIter_Next(en->en_sit);
+	if (next_item == NULL)
+		return NULL;
+
+	result = PyTuple_New(2);
+	if (result == NULL) {
+		Py_DECREF(next_item);
+		return NULL;
+	}
+
+	next_index = PyInt_FromLong(en->en_index++);
+	if (next_index == NULL) {
+		Py_DECREF(next_item);
+		Py_DECREF(result);
+		return NULL;
+	}
+
+	PyTuple_SET_ITEM(result, 0, next_index);
+	PyTuple_SET_ITEM(result, 1, next_item);
+	return result;
+}
+
+static PyObject *
+enum_getiter(PyObject *en)
+{
+	Py_INCREF(en);
+	return en;
+}
+
+static PyMethodDef enum_methods[] = {
+	{"next",    (PyCFunction)enum_next, METH_NOARGS,
+	 "return the next (index, value) pair, or raise StopIteration"},
+	{NULL,      NULL}       /* sentinel */
+};
+
+static char enum_doc[] =
+	"enumerate(iterable) -> create an enumerating-iterator";
+
+PyTypeObject PyEnum_Type = {
+	PyObject_HEAD_INIT(&PyType_Type)
+	0,                              /* ob_size */
+	"enumerate",                    /* tp_name */
+	sizeof(enumobject),             /* tp_basicsize */
+	0,                              /* tp_itemsize */
+	/* methods */
+	(destructor)enum_dealloc,       /* tp_dealloc */
+	0,                              /* tp_print */
+	0,                              /* tp_getattr */
+	0,                              /* tp_setattr */
+	0,                              /* tp_compare */
+	0,                              /* tp_repr */
+	0,                              /* tp_as_number */
+	0,                              /* tp_as_sequence */
+	0,                              /* tp_as_mapping */
+	0,                              /* tp_hash */
+	0,                              /* tp_call */
+	0,                              /* tp_str */
+	PyObject_GenericGetAttr,        /* tp_getattro */
+	0,                              /* tp_setattro */
+	0,                              /* tp_as_buffer */
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+		Py_TPFLAGS_BASETYPE,    /* tp_flags */
+	enum_doc,                       /* tp_doc */
+	(traverseproc)enum_traverse,    /* tp_traverse */
+	0,                              /* tp_clear */
+	0,                              /* tp_richcompare */
+	0,                              /* tp_weaklistoffset */
+	(getiterfunc)enum_getiter,      /* tp_iter */
+	(iternextfunc)enum_next,        /* tp_iternext */
+	enum_methods,                   /* tp_methods */
+	0,                              /* tp_members */
+	0,                              /* tp_getset */
+	0,                              /* tp_base */
+	0,                              /* tp_dict */
+	0,                              /* tp_descr_get */
+	0,                              /* tp_descr_set */
+	0,                              /* tp_dictoffset */
+	0,                              /* tp_init */
+	PyType_GenericAlloc,            /* tp_alloc */
+	enum_new,                       /* tp_new */
+	PyObject_GC_Del,                /* tp_free */
+};