From 024e4e1ebb9a7b3fe1425aa800ef2f07ae1b146b Mon Sep 17 00:00:00 2001
From: Taeknology <20297177+Taeknology@users.noreply.github.com>
Date: Sun, 2 Aug 2026 19:35:39 +0900
Subject: [PATCH 1/3] gh-150942: Use reference-stealing append in
 BytesIO.readlines

---
 Modules/_io/bytesio.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/Modules/_io/bytesio.c b/Modules/_io/bytesio.c
index 7d6053d85cd9e4a..fa3778c12273ca5 100644
--- a/Modules/_io/bytesio.c
+++ b/Modules/_io/bytesio.c
@@ -1,5 +1,6 @@
 #include "Python.h"
 #include "pycore_critical_section.h"  // Py_BEGIN_CRITICAL_SECTION()
+#include "pycore_list.h"              // _PyList_AppendTakeRef()
 #include "pycore_object.h"
 #include "pycore_pyatomic_ft_wrappers.h"
 #include "pycore_sysmodule.h"         // _PySys_GetSizeOf()
@@ -663,11 +664,9 @@ _io_BytesIO_readlines_impl(bytesio *self, PyObject *arg)
         line = PyBytes_FromStringAndSize(output, n);
         if (!line)
             goto on_error;
-        if (PyList_Append(result, line) == -1) {
-            Py_DECREF(line);
+        if (_PyList_AppendTakeRef((PyListObject *)result, line) < 0) {
             goto on_error;
         }
-        Py_DECREF(line);
         size += n;
         if (maxsize > 0 && size >= maxsize)
             break;

From 356c57f4b1d3b53ef4cf52bc9b957170911b08f8 Mon Sep 17 00:00:00 2001
From: Taeknology <20297177+Taeknology@users.noreply.github.com>
Date: Tue, 4 Aug 2026 19:50:52 +0900
Subject: [PATCH 2/3] gh-150942: Add NEWS entry for BytesIO.readlines
 optimization

---
 .../next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst

diff --git a/Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst b/Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst
new file mode 100644
index 000000000000000..be50a73a029044c
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst
@@ -0,0 +1,2 @@
+Improve the performance of :meth:`io.BytesIO.readlines`, particularly in
+free-threaded builds.

From 26c3dbbf92d52a93c1307c18f2ffbf3b363abd93 Mon Sep 17 00:00:00 2001
From: Taeknology <20297177+Taeknology@users.noreply.github.com>
Date: Tue, 4 Aug 2026 21:46:53 +0900
Subject: [PATCH 3/3] gh-150942: Fix NEWS cross-reference

---
 .../Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst    | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst b/Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst
index be50a73a029044c..bdc93872f012616 100644
--- a/Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst
+++ b/Misc/NEWS.d/next/Library/2026-08-04-19-50-52.gh-issue-150942.B8ytes.rst
@@ -1,2 +1,2 @@
-Improve the performance of :meth:`io.BytesIO.readlines`, particularly in
-free-threaded builds.
+Improve the performance of :meth:`~io.IOBase.readlines` for
+:class:`io.BytesIO`, particularly in free-threaded builds.