Following to changes in issue45711, the interpreter's internal representation of the active exception is just the exception instance (the exc_type and exc_traceback fields were removed).

For backwards compatibility, sys.exc_info() constructs the (typ, val, tb) tuple from the instance and this will continue to be the case for some time because this tuple has leaked into quite a few APIs.

However, now that the redundancy in the exc_info tuple is guaranteed by the way it's constructed, we can confidently add a sys.exception() method that returns just the exception instance (as suggested in PEP3134's section on future improvements).

This small change will make a difference to learners because the (typ, val, tb) tuple looks quite cryptic to those who don't know about tracebacks, and the redundancy in it is confusing for those who do.

This is part of a larger plan to reduce the footprint of the exc_info triplet on the language. See https://gist.github.com/iritkatriel/3927147548b10a7929cb0b680e3adc52
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Would there be any value in spelling this as sys.active_exception() or sys.current_exception() or sys.get_exception() or sys.exception_in_flight() or similar?

My only worry is confusion between sys.exception() versus builtins.Exception.

So sys.exception() will be equivalent to sys.exc_info()[1] (or rather, sys.exc_info() will be (type(sys.exception()), sys.exception(), sys.exception().__traceback__))?

That seems good to me.

FWIW, here's an alternative we should *not* pursue:  return just the exception from sys.exc_info().  For compatibility, we would implement `__iter__` and `__getitem__` on BaseException, to duplicate the behavior of the current tuple.  There are a number of good reasons why this is *not* what we should do.

I thought of something like sys.active_exception() but it seems like a lot to type. sys.exception() was suggested in pep3134.


Does this change need a pep?

sys.exception() seems like a decent enough trade-off.  I've always disliked the abbreviations in "exc_info".  It doesn't feel big enough for a PEP to me.

Cool. I just removed the do-not-merge label from the PR and I guess it's ready to be reviewed.

New changeset c590b581bba517f81ced2e6f531ccc9e2e22eab5 by Irit Katriel in branch 'main':
bpo-46328: Add sys.exception() (GH-30514)
https://github.com/python/cpython/commit/c590b581bba517f81ced2e6f531ccc9e2e22eab5