There is precedent with Python 2’s “raise” statement for accepting an exception instance for the first parameter (where an exception class would otherwise be passed). Also, generator.throw() supports this; see Issue 14911 for clarifying its documentation.

I would support changing the following signatures so that the first parameter could hold the value, not just the type:

print_exception(etype, value=None, tb=None, limit=None, ...)
format_exception_only(etype, value=None)
format_exception(etype, value=None, tb=None, limit=None, ...)
TracebackException(exc_type, exc_value=None, exc_traceback=None, *, ...)