This issue tracker has been migrated to GitHub, and is currently read-only.
For more information, see the GitHub FAQs in the Python's Developer Guide.

Author terry.reedy
Recipients andrei.avk, kj, pablogsal, terry.reedy
Date 2021-09-24.22:13:12
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
In 3.10+, end_lineno and end_offset fields were added to SyntaxError objects and the args tuple.

>>> try: compile('1 1', '', 'single')
... except SyntaxError as e: print(e.args)
('invalid syntax. Perhaps you forgot a comma?', ('', 1, 1, '1 1', 1, 4))

Here, line 1, offset 4 is the first 1-based column not part of the error.

The builtin default sys.excepthook was modified to read and use this new information and mark (end_offset - offset) columns with '^'s.  This default prints what it does to sys.stderr.

The syntax error formatting in the traceback module was not altered.  However, a new method, TracebackException._format_syntax_error, was extracted from TracebackException.format_exception_only so that the former could be overridden by software that simulates interaction.

The printed traceback does not come from line 1348.  That *executes* the user code, but all Exceptions, including SyntaxError, are caught.  If the exception is not expected and the run is not quiet, the exception is output by report_unexpected_exception(), as seen above as 'OUTPUT' and the lines that follows.

This calls _exception_traceback(exc_info).
This calls traceback.print_exception, which I believe, for syntax errors, ultimately calls TracebackException._format_syntax_error.

I believe that the options for a fix are either
1. Call default sys.excepthook while capturing its output into a StringIO instance.
2. Assuming I am correct above about _format_syntax_error being called, monkeypatch it.  In line 779,
replace '^' with a field with a calculated number of ^s.

I need to do one of these two for IDLE, and may try both.
Date User Action Args
2021-09-24 22:13:12terry.reedysetrecipients: + terry.reedy, pablogsal, kj, andrei.avk
2021-09-24 22:13:12terry.reedysetmessageid: <>
2021-09-24 22:13:12terry.reedylinkissue45249 messages
2021-09-24 22:13:12terry.reedycreate