[Python-ideas] raising an exception type doesn't instantiate it until it gets caught

[Cameron Simpson]

On 07Nov2011 04:04, Antoine Pitrou <solipsis at pitrou.net> wrote:
| On Mon, 7 Nov 2011 12:03:46 +1000
| Nick Coghlan <ncoghlan at gmail.com> wrote:
| > > I'm not sure that it's still that important -- in fact I'm not sure Python 3
| > > still has this behavior.
| > 
| > I'm fairly sure it does (it was the 3.x version of ceval that I was
| > reading to remind myself of how the stack unwinding process actually
| > works and the call to PyErr_NormalizeException() is still in there).
| > It's just that without the multiple argument forms of the raise
| > statement, pure Python code can only exploit it for exceptions without
| > any arguments (so it still works for the StopIteration optimisation).
| 
| It's too late for me to go and take a look, but I'm not sure it does.
| Unless the performance loss is significant, I would be in favour of
| simplifying all this and always instantiating exceptions. Exception
| handling in the eval loop and exception "normalization" is a nasty area
| of the interpreter.

I presume StopIteration would get instantiated to a singleton, like
NoneType to None? Just asking.
-- 
Cameron Simpson <cs at zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

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