From ac555bc90352e6da424129a8a51f43545c81731c Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 02:15:55 +0200
Subject: [PATCH 01/21] Implement `AttributeError_str()`

---
 Objects/exceptions.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 149595e64cec144..0833791d5c707aa 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2702,6 +2702,23 @@ AttributeError_dealloc(PyObject *self)
     Py_TYPE(self)->tp_free(self);
 }
 
+static PyObject *
+AttributeError_str(PyObject *op)
+{
+    PyAttributeErrorObject *self = PyAttributeErrorObject_CAST(op);
+    if (
+        self->obj
+        && (!PyTuple_GET_SIZE(self->args)
+        || (PyTuple_GET_SIZE(self->args) == 1
+            && PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name))
+        )
+    ) {
+        return PyUnicode_FromFormat("%R has no attribute '%U'",
+                                    self->obj, self->name);
+    }
+    return BaseException_str(op);
+}
+
 static int
 AttributeError_traverse(PyObject *op, visitproc visit, void *arg)
 {
@@ -2770,7 +2787,7 @@ static PyMethodDef AttributeError_methods[] = {
 ComplexExtendsException(PyExc_Exception, AttributeError,
                         AttributeError, 0,
                         AttributeError_methods, AttributeError_members,
-                        0, BaseException_str, 0, "Attribute not found.");
+                        0, AttributeError_str, 0, "Attribute not found.");
 
 /*
  *    SyntaxError extends Exception

From 4f22a162a15bc7cab7892b2dd96d8eb611128e08 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 02:34:00 +0200
Subject: [PATCH 02/21] Add tests

---
 Lib/test/test_exceptions.py | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index cc7faef93e1af7c..36a6d718f06ece0 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -10,6 +10,7 @@
 from codecs import BOM_UTF8
 from itertools import product
 from textwrap import dedent
+from types import ModuleType
 
 from test.support import (captured_stderr, check_impl_detail,
                           cpython_only, gc_collect,
@@ -2047,6 +2048,38 @@ def blech(self):
             self.assertEqual("bluch", exc.name)
             self.assertEqual(obj, exc.obj)
 
+    def _test_generated_message(self, obj, name):
+        with self.assertRaises(AttributeError) as cm:
+            getattr(obj, name)
+        self.assertEqual(str(cm.exception),
+                         f"{obj!r} has no attribute {name!r}")
+
+    def test_getattr_error_message(self):
+        class RaiseWithName:
+            def __getattr__(self, name):
+                raise AttributeError(name)
+
+        class BareRaise:
+            def __getattr__(self, name):
+                raise AttributeError
+
+        self._test_generated_message(RaiseWithName(), "missing1")
+        self._test_generated_message(BareRaise(), "missing2")
+
+    def test_module_getattr_attribute_error_message(self):
+        mod1 = ModuleType("raisewithname")
+        def raise_with_name(name):
+            raise AttributeError(name)
+        mod1.__getattr__ = raise_with_name
+
+        mod2 = ModuleType("bareraise")
+        def bare_raise(name):
+            raise AttributeError
+        mod2.__getattr__ = bare_raise
+
+        self._test_generated_message(mod1, "missing3")
+        self._test_generated_message(mod2, "missing4")
+
     # Note: name suggestion tests live in `test_traceback`.
 
 

From b30d6768cb96bc35f4d8e4d1983e91fec51c09b1 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 02:41:04 +0200
Subject: [PATCH 03/21] Check name too

---
 Objects/exceptions.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 0833791d5c707aa..6fa2c2f8f149ec0 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2708,6 +2708,7 @@ AttributeError_str(PyObject *op)
     PyAttributeErrorObject *self = PyAttributeErrorObject_CAST(op);
     if (
         self->obj
+        && self->name
         && (!PyTuple_GET_SIZE(self->args)
         || (PyTuple_GET_SIZE(self->args) == 1
             && PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name))

From 28e04d3e4213189e44ba539df01aab57ccdbb1fb Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 02:48:03 +0200
Subject: [PATCH 04/21] Add docs

---
 Doc/library/exceptions.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst
index 3775d5ac81a2736..59ba5ca49b491f0 100644
--- a/Doc/library/exceptions.rst
+++ b/Doc/library/exceptions.rst
@@ -215,9 +215,18 @@ The following exceptions are the exceptions that are usually raised.
 
       The object that was accessed for the named attribute.
 
+   When possible, :attr:`name` and :attr:`obj` are set automatically
+   for failed attribute lookups.
+
    .. versionchanged:: 3.10
       Added the :attr:`name` and :attr:`obj` attributes.
 
+   .. versionchanged:: next
+      The default error message is now generated from :attr:`name` and
+      :attr:`obj` when both attributes are set and the exception was
+      constructed with no positional arguments, or with a single positional
+      argument equal to :attr:`name`.
+
 .. exception:: EOFError
 
    Raised when the :func:`input` function hits an end-of-file condition (EOF)

From e5c49220c73dcf84efed95ee15fded200e9c1e97 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 02:53:16 +0200
Subject: [PATCH 05/21] Add news entry

---
 .../2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst            | 4 ++++
 1 file changed, 4 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
new file mode 100644
index 000000000000000..e3bcea972ca4cbd
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
@@ -0,0 +1,4 @@
+The default error message is now generated from ``name`` and
+``obj`` attributes of :exc:`AttributeError` when both are set and
+the exception was constructed with no positional arguments, or with
+a single positional argument equal to :attr:`name`. Patch by Bartosz Sławecki.

From 38545635df41c999dd9d0ef64ab33ca074a0f2ff Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 02:55:13 +0200
Subject: [PATCH 06/21] Improve formatting

---
 Objects/exceptions.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 6fa2c2f8f149ec0..d3f4eba3ed9a442 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2710,8 +2710,8 @@ AttributeError_str(PyObject *op)
         self->obj
         && self->name
         && (!PyTuple_GET_SIZE(self->args)
-        || (PyTuple_GET_SIZE(self->args) == 1
-            && PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name))
+            || (PyTuple_GET_SIZE(self->args) == 1
+                && PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name))
         )
     ) {
         return PyUnicode_FromFormat("%R has no attribute '%U'",

From 1e88331004cdbb0aa90e9e01233adaa55787880d Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 03:01:05 +0200
Subject: [PATCH 07/21] Simplify?

---
 Objects/exceptions.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index d3f4eba3ed9a442..dd55642130c46fc 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2706,18 +2706,14 @@ static PyObject *
 AttributeError_str(PyObject *op)
 {
     PyAttributeErrorObject *self = PyAttributeErrorObject_CAST(op);
-    if (
-        self->obj
-        && self->name
-        && (!PyTuple_GET_SIZE(self->args)
-            || (PyTuple_GET_SIZE(self->args) == 1
-                && PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name))
-        )
-    ) {
-        return PyUnicode_FromFormat("%R has no attribute '%U'",
-                                    self->obj, self->name);
+    if (!self->obj || !self->name || PyTuple_GET_SIZE(self->args) > 1
+        || (PyTuple_GET_SIZE(self->args) == 1 &&
+            !PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name)))
+    {
+        return BaseException_str(op);
     }
-    return BaseException_str(op);
+    return PyUnicode_FromFormat("%R has no attribute '%U'",
+                                self->obj, self->name);
 }
 
 static int

From 2fd216a0255da824db4c4e91d2f8cb562bd29961 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 03:06:59 +0200
Subject: [PATCH 08/21] Cooler formatting of the news entry

---
 .../2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst        | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
index e3bcea972ca4cbd..278bc2ac64abeba 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
@@ -1,4 +1,4 @@
-The default error message is now generated from ``name`` and
-``obj`` attributes of :exc:`AttributeError` when both are set and
-the exception was constructed with no positional arguments, or with
-a single positional argument equal to :attr:`name`. Patch by Bartosz Sławecki.
+The default error message is now generated from ``name`` and ``obj`` attributes
+of :exc:`AttributeError` when both are set and the exception was constructed with
+no positional arguments, or with a single positional argument equal to :attr:`name`.
+Patch by Bartosz Sławecki.

From 356f56eeac4fdd2dc5724541ad1e70fc0a711ee5 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 03:13:38 +0200
Subject: [PATCH 09/21] Test custom messages aren't overwritten

---
 Lib/test/test_exceptions.py | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 36a6d718f06ece0..7d08369549206e6 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -2063,8 +2063,13 @@ class BareRaise:
             def __getattr__(self, name):
                 raise AttributeError
 
+        class RaiseCustom:
+            def __getattr__(self, name):
+                raise AttributeError("custom")
+
         self._test_generated_message(RaiseWithName(), "missing1")
         self._test_generated_message(BareRaise(), "missing2")
+        self._test_generated_message(RaiseCustom(), "custom")
 
     def test_module_getattr_attribute_error_message(self):
         mod1 = ModuleType("raisewithname")
@@ -2077,8 +2082,14 @@ def bare_raise(name):
             raise AttributeError
         mod2.__getattr__ = bare_raise
 
+        mod3 = ModuleType("bareraise")
+        def raise_custom(name):
+            raise AttributeError("custom")
+        mod3.__getattr__ = raise_custom
+
         self._test_generated_message(mod1, "missing3")
         self._test_generated_message(mod2, "missing4")
+        self._test_generated_message(mod3, "custom")
 
     # Note: name suggestion tests live in `test_traceback`.
 

From 8db03948be57346ea359b79dccbdb86165f02c2c Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 03:17:49 +0200
Subject: [PATCH 10/21] Fix news problem

---
 .../2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst              | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
index 278bc2ac64abeba..2852419c6d6e8a7 100644
--- a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-16-02-50-01.gh-issue-153785.fJqPKC.rst
@@ -1,4 +1,4 @@
 The default error message is now generated from ``name`` and ``obj`` attributes
 of :exc:`AttributeError` when both are set and the exception was constructed with
-no positional arguments, or with a single positional argument equal to :attr:`name`.
+no positional arguments, or with a single positional argument equal to ``name``.
 Patch by Bartosz Sławecki.

From ebcc7958b59acdbb751a9c777d7b071aa7e756f1 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 03:20:19 +0200
Subject: [PATCH 11/21] Shorter test name

---
 Lib/test/test_exceptions.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 7d08369549206e6..5c04a02adf29f59 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -2071,7 +2071,7 @@ def __getattr__(self, name):
         self._test_generated_message(BareRaise(), "missing2")
         self._test_generated_message(RaiseCustom(), "custom")
 
-    def test_module_getattr_attribute_error_message(self):
+    def test_module_getattr_error_message(self):
         mod1 = ModuleType("raisewithname")
         def raise_with_name(name):
             raise AttributeError(name)

From b6fda10e9d3b1084b5f3ba6b2f5140448c6644f8 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 03:21:18 +0200
Subject: [PATCH 12/21] Fix inconsistent style

---
 Objects/exceptions.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index dd55642130c46fc..50056635d0afdbe 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2707,8 +2707,8 @@ AttributeError_str(PyObject *op)
 {
     PyAttributeErrorObject *self = PyAttributeErrorObject_CAST(op);
     if (!self->obj || !self->name || PyTuple_GET_SIZE(self->args) > 1
-        || (PyTuple_GET_SIZE(self->args) == 1 &&
-            !PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name)))
+        || (PyTuple_GET_SIZE(self->args) == 1
+            && !PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name)))
     {
         return BaseException_str(op);
     }

From d624835c7f72a6fcd1a61a43bec957d2c6eff51d Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 04:20:38 +0200
Subject: [PATCH 13/21] Make thread-safe, presumably

---
 Objects/exceptions.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 50056635d0afdbe..aff5c19c578b52c 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2706,14 +2706,24 @@ static PyObject *
 AttributeError_str(PyObject *op)
 {
     PyAttributeErrorObject *self = PyAttributeErrorObject_CAST(op);
-    if (!self->obj || !self->name || PyTuple_GET_SIZE(self->args) > 1
+    PyObject *ret, *arg;
+    Py_BEGIN_CRITICAL_SECTION(self);
+    if (
+        !self->obj || !self->name || !PyUnicode_Check(self->name)
+        || PyTuple_GET_SIZE(self->args) > 1
         || (PyTuple_GET_SIZE(self->args) == 1
-            && !PyUnicode_Equal(PyTuple_GET_ITEM(self->args, 0), self->name)))
-    {
-        return BaseException_str(op);
+            && PyUnicode_Check(arg = PyTuple_GET_ITEM(self->args, 0))
+            && !PyUnicode_Equal(arg, self->name))
+    ) {
+        ret = BaseException_str(op);
+    }
+    else {
+        ret = PyUnicode_FromFormat("%R has no attribute '%U'",
+                                    self->obj, self->name);
     }
-    return PyUnicode_FromFormat("%R has no attribute '%U'",
-                                self->obj, self->name);
+    Py_END_CRITICAL_SECTION();
+    return ret;
+
 }
 
 static int

From c50a356e4e3cff2363cb130d6eec20dd68aee6c4 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 04:23:31 +0200
Subject: [PATCH 14/21] Rarest case goes last

---
 Objects/exceptions.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index aff5c19c578b52c..a339d848a8a2ade 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2710,10 +2710,10 @@ AttributeError_str(PyObject *op)
     Py_BEGIN_CRITICAL_SECTION(self);
     if (
         !self->obj || !self->name || !PyUnicode_Check(self->name)
-        || PyTuple_GET_SIZE(self->args) > 1
         || (PyTuple_GET_SIZE(self->args) == 1
             && PyUnicode_Check(arg = PyTuple_GET_ITEM(self->args, 0))
             && !PyUnicode_Equal(arg, self->name))
+        || PyTuple_GET_SIZE(self->args) != 0
     ) {
         ret = BaseException_str(op);
     }

From 7ad5204f0e29ca83fdc87516c693bd6c3f87e926 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 04:24:10 +0200
Subject: [PATCH 15/21] } else {

---
 Objects/exceptions.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index a339d848a8a2ade..6bab5e706db8205 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2716,8 +2716,7 @@ AttributeError_str(PyObject *op)
         || PyTuple_GET_SIZE(self->args) != 0
     ) {
         ret = BaseException_str(op);
-    }
-    else {
+    } else {
         ret = PyUnicode_FromFormat("%R has no attribute '%U'",
                                     self->obj, self->name);
     }

From b65a7fddb074fa40274cbffae728cf1189d13436 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 04:26:44 +0200
Subject: [PATCH 16/21] Remove unnecessary whitespace

---
 Objects/exceptions.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 6bab5e706db8205..ad1cc9a77ca21a2 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2722,7 +2722,6 @@ AttributeError_str(PyObject *op)
     }
     Py_END_CRITICAL_SECTION();
     return ret;
-
 }
 
 static int

From e99d87553694bafe9ea623e5db3e8fcdc2e483ff Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 04:27:02 +0200
Subject: [PATCH 17/21] Fix style

---
 Objects/exceptions.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index ad1cc9a77ca21a2..64f6a8cc948bae9 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2718,7 +2718,7 @@ AttributeError_str(PyObject *op)
         ret = BaseException_str(op);
     } else {
         ret = PyUnicode_FromFormat("%R has no attribute '%U'",
-                                    self->obj, self->name);
+                                   self->obj, self->name);
     }
     Py_END_CRITICAL_SECTION();
     return ret;

From 8c29de3460602e9bd4260df966f4faa174d6a1b7 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 04:37:36 +0200
Subject: [PATCH 18/21] Avoid nesting critical sections!

---
 Objects/exceptions.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 64f6a8cc948bae9..786f57bbc6c0b37 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2706,21 +2706,22 @@ static PyObject *
 AttributeError_str(PyObject *op)
 {
     PyAttributeErrorObject *self = PyAttributeErrorObject_CAST(op);
-    PyObject *ret, *arg;
+    PyObject *ret = NULL, *arg;
     Py_BEGIN_CRITICAL_SECTION(self);
     if (
-        !self->obj || !self->name || !PyUnicode_Check(self->name)
-        || (PyTuple_GET_SIZE(self->args) == 1
-            && PyUnicode_Check(arg = PyTuple_GET_ITEM(self->args, 0))
-            && !PyUnicode_Equal(arg, self->name))
-        || PyTuple_GET_SIZE(self->args) != 0
+        self->obj && self->name && PyUnicode_Check(self->name)
+        && ((PyTuple_GET_SIZE(self->args) == 1
+             && PyUnicode_Check(arg = PyTuple_GET_ITEM(self->args, 0))
+             && PyUnicode_Equal(arg, self->name))
+            || PyTuple_GET_SIZE(self->args) == 0)
     ) {
-        ret = BaseException_str(op);
-    } else {
         ret = PyUnicode_FromFormat("%R has no attribute '%U'",
                                    self->obj, self->name);
     }
     Py_END_CRITICAL_SECTION();
+    if (!ret) {
+        ret = BaseException_str(op);
+    }
     return ret;
 }
 

From 6faf358eb22dd52a3fcb054921b1ad34bd952bc4 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 05:48:55 +0200
Subject: [PATCH 19/21] Fix error handling, crete strong refs for interpolation

---
 Objects/exceptions.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 786f57bbc6c0b37..3760b17facd0d44 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2706,23 +2706,29 @@ static PyObject *
 AttributeError_str(PyObject *op)
 {
     PyAttributeErrorObject *self = PyAttributeErrorObject_CAST(op);
-    PyObject *ret = NULL, *arg;
+    PyObject *arg, *obj = NULL, *name;
+
     Py_BEGIN_CRITICAL_SECTION(self);
-    if (
-        self->obj && self->name && PyUnicode_Check(self->name)
+    if (self->obj && self->name && PyUnicode_Check(self->name)
         && ((PyTuple_GET_SIZE(self->args) == 1
              && PyUnicode_Check(arg = PyTuple_GET_ITEM(self->args, 0))
              && PyUnicode_Equal(arg, self->name))
-            || PyTuple_GET_SIZE(self->args) == 0)
-    ) {
-        ret = PyUnicode_FromFormat("%R has no attribute '%U'",
-                                   self->obj, self->name);
+            || PyTuple_GET_SIZE(self->args) == 0))
+    {
+        obj = Py_NewRef(self->obj);
+        name = Py_NewRef(self->name);
     }
     Py_END_CRITICAL_SECTION();
-    if (!ret) {
-        ret = BaseException_str(op);
+
+    if (!obj) {
+        return BaseException_str(op);
     }
-    return ret;
+
+    PyObject *result = PyUnicode_FromFormat("%R has no attribute '%U'",
+                                            obj, name);
+    Py_DECREF(obj);
+    Py_DECREF(name);
+    return result;
 }
 
 static int

From 086a0c947bf4cde5942691015bd8bbe54f856c08 Mon Sep 17 00:00:00 2001
From: johnslavik <bartosz@slawecki.dev>
Date: Thu, 16 Jul 2026 05:52:11 +0200
Subject: [PATCH 20/21] Multiline if properly done

---
 Objects/exceptions.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 3760b17facd0d44..c460f109c5d2881 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -2709,12 +2709,13 @@ AttributeError_str(PyObject *op)
     PyObject *arg, *obj = NULL, *name;
 
     Py_BEGIN_CRITICAL_SECTION(self);
-    if (self->obj && self->name && PyUnicode_Check(self->name)
+    if (
+        self->obj && self->name && PyUnicode_Check(self->name)
         && ((PyTuple_GET_SIZE(self->args) == 1
              && PyUnicode_Check(arg = PyTuple_GET_ITEM(self->args, 0))
              && PyUnicode_Equal(arg, self->name))
-            || PyTuple_GET_SIZE(self->args) == 0))
-    {
+            || PyTuple_GET_SIZE(self->args) == 0)
+    ) {
         obj = Py_NewRef(self->obj);
         name = Py_NewRef(self->name);
     }

From e5bb17e5b1555b955d01568f500f9b447b6bdcd5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartosz=20S=C5=82awecki?= <bartosz@ilikepython.com>
Date: Fri, 17 Jul 2026 01:25:53 +0200
Subject: [PATCH 21/21] Fix small text mistake in tests

---
 Lib/test/test_exceptions.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 5c04a02adf29f59..94b69a9a494551a 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -2082,7 +2082,7 @@ def bare_raise(name):
             raise AttributeError
         mod2.__getattr__ = bare_raise
 
-        mod3 = ModuleType("bareraise")
+        mod3 = ModuleType("custom")
         def raise_custom(name):
             raise AttributeError("custom")
         mod3.__getattr__ = raise_custom