Issue #7410: deepcopy of itertools.count() erroneously reset the count.

Lib/test/test_itertools.py

@@ -5,6 +5,8 @@ from weakref import proxy
 import sys
 import operator
 import random
+import copy
+import pickle
 maxsize = test_support.MAX_Py_ssize_t
 minsize = -maxsize-1
 
@@ -215,6 +217,13 @@ class TestBasicOps(unittest.TestCase):
             r2 = 'count(%r)'.__mod__(i).replace('L', '')
             self.assertEqual(r1, r2)
 
+        # check copy, deepcopy, pickle
+        for value in -3, 3, sys.maxint-5, sys.maxint+5:
+            c = count(value)
+            self.assertEqual(next(copy.copy(c)), value)
+            self.assertEqual(next(copy.deepcopy(c)), value)
+            self.assertEqual(next(pickle.loads(pickle.dumps(c))), value)
+
     def test_cycle(self):
         self.assertEqual(take(10, cycle('abc')), list('abcabcabca'))
         self.assertEqual(list(cycle('')), [])

Misc/NEWS

@@ -33,6 +33,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #7410: deepcopy of itertools.count() erroneously reset the count.
+
 - Issue #7403: logging: Fixed possible race condition in lock creation.
 
 - Issue #7341: Close the internal file object in the TarFile constructor in

Modules/itertoolsmodule.c

@@ -2906,6 +2906,21 @@ count_repr(countobject *lz)
 	return result;
 }
 
+static PyObject *
+count_reduce(countobject *lz)
+{
+	if (lz->cnt == PY_SSIZE_T_MAX)
+		return Py_BuildValue("O(O)", Py_TYPE(lz), lz->long_cnt);
+	return Py_BuildValue("O(n)", Py_TYPE(lz), lz->cnt);
+}
+
+PyDoc_STRVAR(count_reduce_doc, "Return state information for pickling.");
+
+static PyMethodDef count_methods[] = {
+	{"__reduce__",	(PyCFunction)count_reduce,	METH_NOARGS,
+	 count_reduce_doc},
+};
+
 PyDoc_STRVAR(count_doc,
 "count([firstval]) --> count object\n\
 \n\
@@ -2941,7 +2956,7 @@ static PyTypeObject count_type = {
 	0,				/* tp_weaklistoffset */
 	PyObject_SelfIter,		/* tp_iter */
 	(iternextfunc)count_next,	/* tp_iternext */
-	0,				/* tp_methods */
+	count_methods,				/* tp_methods */
 	0,				/* tp_members */
 	0,				/* tp_getset */
 	0,				/* tp_base */