[Python-ideas] Arguments to exceptions

[Brendan Barnwell]

On 2017-07-04 13:54, Terry Reedy wrote:
> There have been many proposals for what we might call RichExceptions,
> with more easily access information.  But as Raymond Hettinger keeps
> pointing out, Python does not use exceptions only for (hopefully rare)
> errors.  It also uses them as signals for flow control, both as an
> alternative form for alternation and for iteration.  Alternation with
> try:except instead of if:else is common.  In the try: unicode example
> above, the NameError is not an error.  Until 2.2, IndexError served the
> role of StopIteration today, and can still be used for iteration.  For
> flow control, richer exceptions just slow code execution.

	How significant is this slowdown in practical terms?  Rejecting all 
"rich" exceptions just because they might add a bit of a slowdown seems 
premature to me.  The information available from the rich exceptions has 
value that may or may not outweigh the performance hit.

-- 
Brendan Barnwell
"Do not follow where the path may lead.  Go, instead, where there is no 
path, and leave a trail."
    --author unknown