Add sys.last_exc, deprecate sys.last_type, sys.last_value and sys.last_traceback

[iritkatriel]

Linked PRs

• gh-102778: Add sys.last_exc, deprecate sys.last_type, sys.last_value,sys.last_traceback #102779
• gh-102778: revert changes to idlelib #102825
• gh-102778: IDLE - make sys.last_exc available in Shell after traceback #103314
• gh-102778: update documentation of PyErr_PrintEx and traceback.print_last() regarding sys.last_exc #105190
• [3.12] gh-102778: update documentation of PyErr_PrintEx and traceback.print_last() regarding sys.last_exc (GH-105190) #105246

[terryjreedy]

I appreciate the effort to remove the traces of string exceptions. Is there a plan to actually stop adding the old last_xxx vars to sys and accessing them in other non-IDLE stdlib modules? When they are added to sys by python itself (after unhandled exceptions), could they be added as properties with a getter that would emit a deprecation warning, or are properties for python-coded classes only?

[iritkatriel]

Yes, I would like to eventually remove the old fields.

Since they are module level variables, I don't think they can be properties. But maybe there's something we can do through intercepting getattr on the module?