From 03dd6a2cfca659186d6166c839474b57b8a3f637 Mon Sep 17 00:00:00 2001
From: Justin Applegate <justink.applegate@gmail.com>
Date: Mon, 16 Jun 2025 11:56:46 -0400
Subject: [PATCH 1/2] Add a check for 0 items to `APPENDS` and `ADDITEMS`
 opcodes

---
 Lib/pickle.py            | 4 ++++
 Lib/test/pickletester.py | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/Lib/pickle.py b/Lib/pickle.py
index beaefae0479d3c..4639c4185f6786 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -1785,6 +1785,8 @@ def load_append(self):
     def load_appends(self):
         items = self.pop_mark()
         list_obj = self.stack[-1]
+        if len(items) == 0: # nothing to do
+            return
         try:
             extend = list_obj.extend
         except AttributeError:
@@ -1818,6 +1820,8 @@ def load_setitems(self):
     def load_additems(self):
         items = self.pop_mark()
         set_obj = self.stack[-1]
+        if len(items) == 0: # nothing to do
+            return
         if isinstance(set_obj, set):
             set_obj.update(items)
         else:
diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index 9a3a26a8400844..49ad285da6f10b 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -1105,6 +1105,10 @@ def test_large_binstring(self):
         with self.assertRaisesRegex(pickle.UnpicklingError, errmsg):
             self.loads(b'T\0\0\0\x80')
 
+    def test_appends_additems_no_items(self):
+        self.assertEqual(self.loads(b'K\x01(e.'), 1)
+        self.assertEqual(self.loads(b'K\x01(\x90.'), 1)
+
     def test_get(self):
         pickled = b'((lp100000\ng100000\nt.'
         unpickled = self.loads(pickled)

From 17717476662c866c79db48bad10a0ac07b926197 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Mon, 16 Jun 2025 16:02:08 +0000
Subject: [PATCH 2/2] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../next/Library/2025-06-16-16-02-05.gh-issue-135573.waQmoA.rst  | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2025-06-16-16-02-05.gh-issue-135573.waQmoA.rst

diff --git a/Misc/NEWS.d/next/Library/2025-06-16-16-02-05.gh-issue-135573.waQmoA.rst b/Misc/NEWS.d/next/Library/2025-06-16-16-02-05.gh-issue-135573.waQmoA.rst
new file mode 100644
index 00000000000000..425896da211658
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-06-16-16-02-05.gh-issue-135573.waQmoA.rst
@@ -0,0 +1 @@
+Adds a check in the ``ADDITEMS`` and ``APPENDS`` opcodes of the Python implementation of :mod:`pickle` to return early if there's no items to add.