[pull] main from python:main

Include/internal/pycore_magic_number.h

@@ -303,6 +303,7 @@ Known values:
     Python 3.16a1 3703 (Replace DELETE_GLOBAL with PUSH_NULL; STORE_GLOBAL)
     Python 3.16a1 3704 (Replace DELETE_ATTR with PUSH_NULL; STORE_ATTR)
     Python 3.16a1 3705 (Add INTRINSIC_ADD_CONDITIONAL_ANNOTATION)
+    Python 3.16a1 3706 (Add INTRINSIC_MATCH_CLASS_ISINSTANCE)
 
     Python 3.17 will start with 3750
 
@@ -312,7 +313,7 @@ Known values:
 
 */
 
-#define PYC_MAGIC_NUMBER 3705
+#define PYC_MAGIC_NUMBER 3706
 /* This is equivalent to converting PYC_MAGIC_NUMBER to 2 bytes
    (little-endian) and then appending b'\r\n'. */
 #define PYC_MAGIC_NUMBER_TOKEN \

Lib/idlelib/editor.py

@@ -1120,19 +1120,50 @@ def _close(self):
 
     def last_mtime(self):
         file = self.io.filename
-        return os.path.getmtime(file) if file else 0
+        if not file:
+            return None
+        try:
+            return os.path.getmtime(file)
+        except OSError:
+            # File is gone or cannot be stat'ed.
+            return None
 
     def focus_in_event(self, event):
         mtime = self.last_mtime()
-        if self.mtime != mtime:
+        if mtime == self.mtime:
+            return
+        if self.mtime is not None and mtime is None:
+            # The file was there and is now gone; reloading cannot work.
+            self.deleted_file_event(event)
+        else:
             self.mtime = mtime
-            if self. askyesno(
+            if self.askyesno(
               'Reload', '"%s"\n\nThis script has been modified by another program.'
               '\nDo you want to reload it?' % self.io.filename, parent=self.text):
                 self.io.loadfile(self.io.filename)
             else:
                 self.set_saved(False)
 
+    def deleted_file_event(self, event):
+        # The file was deleted or renamed while open; ask what to do with the
+        # buffer instead of offering a reload that could only fail.  Forget the
+        # old mtime before showing the dialog so a FocusIn delivered while this
+        # dialog (or a Close/Save As sub-dialog) is open does not reopen it; a
+        # successful Save As restores it via set_saved(True).
+        self.mtime = None
+        dialog = simpledialog.SimpleDialog(
+            self.text,
+            title='File Deleted',
+            text='"%s"\n\nThis file no longer exists.' % self.io.filename,
+            buttons=('Close', 'Save As', 'Ignore'),
+            default=1,
+            cancel=2)
+        choice = dialog.go()
+        if choice == 0:
+            self.close()
+        elif choice == 1:
+            self.io.save_as(event)
+
     def load_extensions(self):
         self.extensions = {}
         self.load_standard_extensions()

Lib/idlelib/idle_test/test_editor.py

@@ -1,7 +1,11 @@
 "Test editor, coverage 53%."
 
 from idlelib import editor
+import os
+import tempfile
+import types
 import unittest
+from pathlib import Path
 from collections import namedtuple
 from unittest import mock
 from test.support import requires
@@ -321,5 +325,81 @@ def test_rmenu_check_copy(self):
         eq(self.window.rmenu_check_cut(), 'normal')
 
 
+class LastMtimeTest(unittest.TestCase):
+    # Exercise last_mtime as an unbound method on a stub; no GUI needed.
+
+    def test_existing_file_returns_mtime(self):
+        with tempfile.TemporaryDirectory() as d:
+            p = os.path.join(d, 'f.py')
+            Path(p).touch()
+            stub = types.SimpleNamespace(io=types.SimpleNamespace(filename=p))
+            self.assertEqual(Editor.last_mtime(stub), os.path.getmtime(p))
+
+    def test_deleted_file_returns_none(self):
+        with tempfile.TemporaryDirectory() as d:
+            p = os.path.join(d, 'gone.py')
+            Path(p).touch()
+            os.remove(p)
+            stub = types.SimpleNamespace(io=types.SimpleNamespace(filename=p))
+            self.assertIsNone(Editor.last_mtime(stub))
+
+    def test_not_yet_created_filename(self):
+        # __init__ calls last_mtime() before self.mtime is set, so last_mtime()
+        # must not read self.mtime (the stub has no mtime attribute).
+        stub = types.SimpleNamespace(
+            io=types.SimpleNamespace(filename='/no/such/file.py'))
+        self.assertIsNone(Editor.last_mtime(stub))
+
+    def test_no_filename_returns_none(self):
+        stub = types.SimpleNamespace(io=types.SimpleNamespace(filename=None))
+        self.assertIsNone(Editor.last_mtime(stub))
+
+
+class DeletedFileEventTest(unittest.TestCase):
+    # Exercise the deleted-file handling as unbound methods; dialog is mocked.
+
+    def make_stub(self):
+        return types.SimpleNamespace(
+            mtime=1.0,
+            text=None,
+            io=types.SimpleNamespace(filename='/gone.py', save_as=mock.Mock()),
+            close=mock.Mock(),
+            set_saved=mock.Mock(),
+            deleted_file_event=mock.Mock(),
+            askyesno=mock.Mock(),
+            last_mtime=lambda: None)
+
+    def test_focus_in_routes_deleted_to_dialog(self):
+        stub = self.make_stub()
+        Editor.focus_in_event(stub, 'event')
+        stub.deleted_file_event.assert_called_once_with('event')
+        stub.askyesno.assert_not_called()
+
+    def _run_choice(self, choice):
+        stub = self.make_stub()
+        with mock.patch.object(editor.simpledialog, 'SimpleDialog') as SD:
+            SD.return_value.go.return_value = choice
+            Editor.deleted_file_event(stub, 'event')
+        return stub
+
+    def test_close_choice_closes_window(self):
+        stub = self._run_choice(0)
+        self.assertTrue(stub.close.called)
+        # mtime is cleared before Close so the queued FocusIn does not reprompt.
+        self.assertIsNone(stub.mtime)
+
+    def test_save_as_choice_clears_mtime_and_saves(self):
+        stub = self._run_choice(1)
+        stub.io.save_as.assert_called_once_with('event')
+        # A cancelled Save As leaves mtime None so it does not reprompt.
+        self.assertIsNone(stub.mtime)
+
+    def test_ignore_choice_clears_mtime(self):
+        stub = self._run_choice(2)
+        self.assertIsNone(stub.mtime)
+        stub.io.save_as.assert_not_called()
+        stub.set_saved.assert_not_called()
+
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)

Lib/idlelib/idle_test/test_run.py

@@ -49,14 +49,15 @@ def __eq__(self, other):
             ('int.reel', AttributeError,
                  "type object 'int' has no attribute 'reel'. "
                  "Did you mean '.real' instead of '.reel'?\n"),  # More in 3.15.
+            (r'raise NameError("123\n456")', NameError, "123\n456\n"),
             )
 
     @force_not_colorized
     def test_get_message(self):
         for code, exc, msg in self.data:
             with self.subTest(code=code):
                 try:
-                    eval(compile(code, '', 'eval'))
+                    exec(compile(code, '', 'exec'))
                 except exc:
                     typ, val, tb = sys.exc_info()
                     actual = run.get_message_lines(typ, val, tb)[0]
@@ -68,15 +69,20 @@ def test_get_message(self):
                        new_callable=lambda: (lambda t, e: None))
     def test_get_multiple_message(self, mock):
         d = self.data
-        data2 = ((d[0], d[1]), (d[1], d[2]), (d[2], d[0]))
+        data2 = ((d[0], d[1]),
+                 (d[1], d[2]),
+                 (d[2], d[3]),
+                 (d[3], d[0]),
+                 (d[1], d[3]),
+                 (d[0], d[2]))
         subtests = 0
         for (code1, exc1, msg1), (code2, exc2, msg2) in data2:
             with self.subTest(codes=(code1,code2)):
                 try:
-                    eval(compile(code1, '', 'eval'))
+                    exec(compile(code1, '', 'exec'))
                 except exc1:
                     try:
-                        eval(compile(code2, '', 'eval'))
+                        exec(compile(code2, '', 'exec'))
                     except exc2:
                         with captured_stderr() as output:
                             run.print_exception()

Lib/idlelib/run.py

@@ -4,7 +4,6 @@
 f'''{sys.executable} -c "__import__('idlelib.run').run.main()"'''
 '.run' is needed because __import__ returns idlelib, not idlelib.run.
 """
-import contextlib
 import functools
 import io
 import linecache
@@ -244,15 +243,8 @@ def show_socket_error(err, address):
 
 
 def get_message_lines(typ, exc, tb):
-    "Return line composing the exception message."
-    if typ in (AttributeError, NameError):
-        # 3.10+ hints are not directly accessible from python (#44026).
-        err = io.StringIO()
-        with contextlib.redirect_stderr(err):
-            sys.__excepthook__(typ, exc, tb)
-        return [err.getvalue().split("\n")[-2] + "\n"]
-    else:
-        return traceback.format_exception_only(typ, exc)
+    "Return lines of the exception message, with any suggestion."
+    return list(traceback.TracebackException(typ, exc, tb).format_exception_only())
 
 
 def print_exception():

Lib/test/test_dict.py

@@ -1424,6 +1424,31 @@ def test_reversed_dict_after_clear_and_restore(self):
         for it in iterators:
             self.assertEqual(list(it), [])
 
+    def test_reversed_dict_keys_changed_during_iteration(self):
+        d = dict.fromkeys(range(10))
+        for i in range(7):
+            del d[i]
+
+        iterators = (
+            reversed(d),
+            reversed(d.keys()),
+            reversed(d.values()),
+            reversed(d.items()),
+        )
+        for it in iterators:
+            next(it)
+
+        # Same size as before, but with different keys below
+        # the iterators' current position.
+        d.clear()
+        d.update(dict.fromkeys(range(10)))
+        for i in range(3, 10):
+            del d[i]
+
+        for it in iterators:
+            with self.assertRaisesRegex(RuntimeError, 'keys changed'):
+                list(it)
+
     def test_dict_copy_order(self):
         # bpo-34320
         od = collections.OrderedDict([('a', 1), ('b', 2)])

Misc/NEWS.d/next/Core_and_Builtins/2026-09-26-15-39-32.gh-issue-158254.qT7vRk.rst

@@ -0,0 +1,3 @@
+Reverse iterators over a :class:`dict` and its views now raise
+:exc:`RuntimeError` if the dictionary's keys change during iteration, like
+forward iterators, instead of yielding entries for the new keys.

Misc/NEWS.d/next/IDLE/2025-08-08-10-50-59.gh-issue-135511.9Rw5Zg.rst

@@ -0,0 +1 @@
+Fix display of :exc:`NameError` and :exc:`AttributeError` with multi-line message.

Misc/NEWS.d/next/IDLE/2026-07-10-19-41-00.gh-issue-153480.EdMt1x.rst

@@ -0,0 +1,4 @@
+Fix IDLE failing to start when opening a file which does not exist yet.
+Fix a traceback when a file open in the IDLE editor is deleted by another
+program; IDLE now asks whether to close the window, save the file elsewhere,
+or ignore it.

Objects/dictobject.c

@@ -6303,6 +6303,12 @@ dictreviter_iter_lock_held(PyDictObject *d, PyObject *self)
             value = entry_ptr->me_value;
         }
     }
+    // We found an element, but did not expect it
+    if (di->len == 0) {
+        PyErr_SetString(PyExc_RuntimeError,
+                        "dictionary keys changed during iteration");
+        goto fail;
+    }
     di->di_pos = i-1;
     di->len--;