bpo-42152: Use PyDict_Contains and PyDict_SetDefault if appropriate. (GH-22986)

If PyDict_GetItemWithError is only used to check whether the key is in dict,
it is better to use PyDict_Contains instead.

And if it is used in combination with PyDict_SetItem, PyDict_SetDefault can
replace the combination.

1 files changed, 6 insertions, 11 deletions

diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index bddd8f4..ed8afef 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -2004,26 +2004,21 @@ fast_save_enter(PicklerObject *self, PyObject *obj)
             self->fast_nesting = -1;
             return 0;
         }
-        if (PyDict_GetItemWithError(self->fast_memo, key)) {
-            Py_DECREF(key);
+        int r = PyDict_Contains(self->fast_memo, key);
+        if (r > 0) {
             PyErr_Format(PyExc_ValueError,
                          "fast mode: can't pickle cyclic objects "
                          "including object type %.200s at %p",
                          Py_TYPE(obj)->tp_name, obj);
-            self->fast_nesting = -1;
-            return 0;
         }
-        if (PyErr_Occurred()) {
-            Py_DECREF(key);
-            self->fast_nesting = -1;
-            return 0;
+        else if (r == 0) {
+            r = PyDict_SetItem(self->fast_memo, key, Py_None);
         }
-        if (PyDict_SetItem(self->fast_memo, key, Py_None) < 0) {
-            Py_DECREF(key);
+        Py_DECREF(key);
+        if (r != 0) {
             self->fast_nesting = -1;
             return 0;
         }
-        Py_DECREF(key);
     }
     return 1;
 }