gh-137716: TracebackException to handle messages with punctuation

Lib/test/test_traceback.py

@@ -3866,6 +3866,50 @@ def test_traceback_header(self):
         exc = traceback.TracebackException(Exception, Exception("haven"), None)
         self.assertEqual(list(exc.format()), ["Exception: haven\n"])
 
+    def test_name_error_punctuation_with_suggestions(self):
+        def format_error(message, name):
+            return self.format_error(NameError, message, name=name)
+
+        test_cases = [
+            ("a.", "time", "NameError: a. Did you forget to import 'time'?\n"),
+            ("b?", "time", "NameError: b? Did you forget to import 'time'?\n"),
+            ("c!", "time", "NameError: c! Did you forget to import 'time'?\n"),
+            ("d", "time", "NameError: d. Did you forget to import 'time'?\n"),
+            ("e", "foo123", "NameError: e\n"),
+        ]
+        for message, name, expected in test_cases:
+            with self.subTest(message=message):
+                message = format_error(message, name)
+                self.assertEqual(message, expected)
+
+        with self.subTest("stdlib module import suggestion"):
+            message = format_error("foo", "abc")
+            expected_message = (
+                "NameError: foo. Did you mean: 'abs'? "
+                "Or did you forget to import 'abc'?\n"
+            )
+            self.assertEqual(message, expected_message)
+
+        with self.subTest("'did you mean' suggestion"):
+            message = format_error("bar", "flaot")
+            expected_message = "NameError: bar. Did you mean: 'float'?\n"
+            self.assertEqual(message, expected_message)
+
+    def test_import_error_punctuation_handling_with_suggestions(self):
+        def format_error(message):
+            return self.format_error(ImportError, message, name="math", name_from="sinq")
+
+        test_cases = [
+            ("a.", "ImportError: a. Did you mean: 'sin'?\n"),
+            ("b?", "ImportError: b? Did you mean: 'sin'?\n"),
+            ("c!", "ImportError: c! Did you mean: 'sin'?\n"),
+            ("d", "ImportError: d. Did you mean: 'sin'?\n"),
+        ]
+        for message, expected in test_cases:
+            with self.subTest(message=message):
+                message = format_error(message)
+                self.assertEqual(message, expected)
+
     @requires_debug_ranges()
     def test_print(self):
         def f():
@@ -3903,6 +3947,14 @@ def test_dont_swallow_cause_or_context_of_falsey_exception(self):
         except FalseyException as e:
             self.assertIn(context_message, traceback.format_exception(e))
 
+    @staticmethod
+    def format_error(exc_type, exc_message, *args, **kwargs):
+        try:
+            raise exc_type(exc_message, *args, **kwargs)
+        except exc_type as e:
+            exc = traceback.TracebackException.from_exception(e)
+            return list(exc.format())[-1]
+
 
 class TestTracebackException_ExceptionGroups(unittest.TestCase):
     def setUp(self):

Lib/traceback.py

@@ -1086,63 +1086,40 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
 
         self._is_syntax_error = False
         self._have_exc_type = exc_type is not None
-        if exc_type is not None:
+
+        if self._have_exc_type:
             self.exc_type_qualname = exc_type.__qualname__
             self.exc_type_module = exc_type.__module__
-        else:
-            self.exc_type_qualname = None
-            self.exc_type_module = None
-
-        if exc_type and issubclass(exc_type, SyntaxError):
-            # Handle SyntaxError's specially
-            self.filename = exc_value.filename
-            lno = exc_value.lineno
-            self.lineno = str(lno) if lno is not None else None
-            end_lno = exc_value.end_lineno
-            self.end_lineno = str(end_lno) if end_lno is not None else None
-            self.text = exc_value.text
-            self.offset = exc_value.offset
-            self.end_offset = exc_value.end_offset
-            self.msg = exc_value.msg
-            self._is_syntax_error = True
-            self._exc_metadata = getattr(exc_value, "_metadata", None)
-        elif exc_type and issubclass(exc_type, ImportError) and \
-                getattr(exc_value, "name_from", None) is not None:
-            wrong_name = getattr(exc_value, "name_from", None)
-            suggestion = _compute_suggestion_error(exc_value, exc_traceback, wrong_name)
-            if suggestion:
-                if suggestion.isascii():
-                    self._str += f". Did you mean: '{suggestion}'?"
-                else:
-                    self._str += f". Did you mean: '{suggestion}' ({suggestion!a})?"
-        elif exc_type and issubclass(exc_type, ModuleNotFoundError):
-            module_name = getattr(exc_value, "name", None)
-            if module_name in sys.stdlib_module_names:
-                message = _MISSING_STDLIB_MODULE_MESSAGES.get(
+            if issubclass(exc_type, SyntaxError):
+                # Handle SyntaxErrors specially
+                self.filename = exc_value.filename
+                lno = exc_value.lineno
+                self.lineno = str(lno) if lno is not None else None
+                end_lno = exc_value.end_lineno
+                self.end_lineno = str(end_lno) if end_lno is not None else None
+                self.text = exc_value.text
+                self.offset = exc_value.offset
+                self.end_offset = exc_value.end_offset
+                self.msg = exc_value.msg
+                self._is_syntax_error = True
+                self._exc_metadata = getattr(exc_value, "_metadata", None)
+            elif (issubclass(exc_type, ModuleNotFoundError)
+                    and getattr(exc_value, "name", None) in sys.stdlib_module_names):
+                module_name = exc_value.name
+                self._str = _MISSING_STDLIB_MODULE_MESSAGES.get(
                     module_name,
                     f"Standard library module {module_name!r} was not found"
                 )
-                self._str = message
-            elif sys.flags.no_site:
-                self._str += (". Site initialization is disabled, did you forget to "
-                    + "add the site-packages directory to sys.path "
-                    + "or to enable your virtual environment?")
-        elif exc_type and issubclass(exc_type, (NameError, AttributeError)) and \
-                getattr(exc_value, "name", None) is not None:
-            wrong_name = getattr(exc_value, "name", None)
-            suggestion = _compute_suggestion_error(exc_value, exc_traceback, wrong_name)
-            if suggestion:
-                if suggestion.isascii():
-                    self._str += f". Did you mean: '{suggestion}'?"
+            elif suggestion := _suggestion_message(exc_type, exc_value, exc_traceback):
+                if self._str.endswith(('.', '?', '!')):
+                    punctuation = ''
                 else:
-                    self._str += f". Did you mean: '{suggestion}' ({suggestion!a})?"
-            if issubclass(exc_type, NameError):
-                wrong_name = getattr(exc_value, "name", None)
-                if wrong_name is not None and wrong_name in sys.stdlib_module_names:
-                    if suggestion:
-                        self._str += f" Or did you forget to import '{wrong_name}'?"
-                    else:
-                        self._str += f". Did you forget to import '{wrong_name}'?"
+                    punctuation = '.'
+                self._str += f"{punctuation} {suggestion}"
+        else:
+            self.exc_type_qualname = None
+            self.exc_type_module = None
+
         if lookup_lines:
             self._load_lines()
         self.__suppress_context__ = \
@@ -1771,6 +1748,42 @@ def _compute_suggestion_error(exc_value, tb, wrong_name):
     return suggestion
 
 
+def _suggestion_message(exc_type, exc_value, exc_traceback):
+    if (
+        issubclass(exc_type, ModuleNotFoundError)
+        and sys.flags.no_site
+        and getattr(exc_value, "name", None) not in sys.stdlib_module_names
+    ):
+        return ("Site initialization is disabled, did you forget to "
+                    "add the site-packages directory to sys.path "
+                    "or to enable your virtual environment?")
+    if issubclass(exc_type, (ImportError, NameError, AttributeError)):
+        if issubclass(exc_type, ImportError):
+            wrong_name = getattr(exc_value, "name_from", None)
+        else:
+            wrong_name = getattr(exc_value, "name", None)
+        if wrong_name:
+            other_name = _compute_suggestion_error(
+                exc_value, exc_traceback, wrong_name
+            )
+            maybe_stdlib_import = (
+                issubclass(exc_type, NameError)
+                and wrong_name in sys.stdlib_module_names
+            )
+            if not other_name:
+                if maybe_stdlib_import:
+                    return f"Did you forget to import '{wrong_name}'?"
+                return None
+            if other_name.isascii():
+                text = f"Did you mean: '{other_name}'?"
+            else:
+                text = f"Did you mean: '{other_name}' ({other_name!a})?"
+            if maybe_stdlib_import:
+                return f"{text} Or did you forget to import '{wrong_name}'?"
+            return text
+    return None
+
+
 def _levenshtein_distance(a, b, max_cost):
     # A Python implementation of Python/suggestions.c:levenshtein_distance.
 

Misc/NEWS.d/next/Core_and_Builtins/2025-08-24-11-42-38.gh-issue-137716.7-Mtj-.rst

@@ -0,0 +1 @@
+Avoid double punctuation in :class:`~traceback.TracebackException` messages