Generalize reduce() to work with iterators.
NEEDS DOC CHANGES.
diff --git a/Lib/test/test_iter.py b/Lib/test/test_iter.py
index 66f40c1..5584587 100644
--- a/Lib/test/test_iter.py
+++ b/Lib/test/test_iter.py
@@ -385,4 +385,17 @@
except OSError:
pass
+ # Test reduces()'s use of iterators.
+ def test_builtin_reduce(self):
+ from operator import add
+ self.assertEqual(reduce(add, SequenceClass(5)), 10)
+ self.assertEqual(reduce(add, SequenceClass(5), 42), 52)
+ self.assertRaises(TypeError, reduce, add, SequenceClass(0))
+ self.assertEqual(reduce(add, SequenceClass(0), 42), 42)
+ self.assertEqual(reduce(add, SequenceClass(1)), 0)
+ self.assertEqual(reduce(add, SequenceClass(1), 42), 42)
+
+ d = {"one": 1, "two": 2, "three": 3}
+ self.assertEqual(reduce(add, d), "".join(d.keys()))
+
run_unittest(TestCase)
diff --git a/Misc/NEWS b/Misc/NEWS
index 617146c..d707a7a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -22,6 +22,7 @@
map()
max()
min()
+ reduce()
What's New in Python 2.1 (final)?
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 0c20d10..5209607 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -1851,26 +1851,25 @@
static PyObject *
builtin_reduce(PyObject *self, PyObject *args)
{
- PyObject *seq, *func, *result = NULL;
- PySequenceMethods *sqf;
- register int i;
+ PyObject *seq, *func, *result = NULL, *it;
if (!PyArg_ParseTuple(args, "OO|O:reduce", &func, &seq, &result))
return NULL;
if (result != NULL)
Py_INCREF(result);
- sqf = seq->ob_type->tp_as_sequence;
- if (sqf == NULL || sqf->sq_item == NULL) {
+ it = PyObject_GetIter(seq);
+ if (it == NULL) {
PyErr_SetString(PyExc_TypeError,
- "reduce() arg 2 must be a sequence");
+ "reduce() arg 2 must support iteration");
+ Py_XDECREF(result);
return NULL;
}
if ((args = PyTuple_New(2)) == NULL)
goto Fail;
- for (i = 0; ; ++i) {
+ for (;;) {
PyObject *op2;
if (args->ob_refcnt > 1) {
@@ -1879,12 +1878,18 @@
goto Fail;
}
- if ((op2 = (*sqf->sq_item)(seq, i)) == NULL) {
- if (PyErr_ExceptionMatches(PyExc_IndexError)) {
- PyErr_Clear();
- break;
+ op2 = PyIter_Next(it);
+ if (op2 == NULL) {
+ /* StopIteration is *implied* by a NULL return from
+ * PyIter_Next() if PyErr_Occurred() is false.
+ */
+ if (PyErr_Occurred()) {
+ if (PyErr_ExceptionMatches(PyExc_StopIteration))
+ PyErr_Clear();
+ else
+ goto Fail;
}
- goto Fail;
+ break;
}
if (result == NULL)
@@ -1903,11 +1908,13 @@
PyErr_SetString(PyExc_TypeError,
"reduce() of empty sequence with no initial value");
+ Py_DECREF(it);
return result;
Fail:
Py_XDECREF(args);
Py_XDECREF(result);
+ Py_DECREF(it);
return NULL;
}