The logical solution to me is to allow any order of while and if, and follow the same 'rule' as multiple for loops - just nest/test those in that order. Then you can have whatever priority you need. One question though is how this should handle multiple loops - break all of them, or just the current one?
- Spencer Brown On 11 Aug 2017, at 6:27 am, Chris Barker <chris.bar...@noaa.gov<mailto:chris.bar...@noaa.gov>> wrote: On Thu, Aug 10, 2017 at 8:39 AM, Paul Moore <p.f.mo...@gmail.com<mailto:p.f.mo...@gmail.com>> wrote: Also, there's a potential issue here - consider [expr for var in even_numbers() if is_odd(var) while var < 100] This is an infinite loop, even though it has a finite termination condition (var < 100), because we only test the termination condition if var is odd, which it never will be. why is the termination only tested if teh if clause is True? Could then not be processed in parallel? or the while first.... so maybe better to do: [expr for var in even_numbers() while var < 100 if is_odd(var)] Maybe it's just me, but I would certainly expect the while to have precedence. I guess I think of it like this: "if" is providing a filtering mechanism "while" is providing a termination mechanism -- is there a use case anyone can think of when they would want the while to be applied to the list AFTER filtering? Obviously, this is a contrived example. And certainly "don't do that, then" is a valid response. But my instinct is that people are going to get this wrong - *especially* in a maintenance environment. sure, but would there be an issue if teh while were given precedence? Overall, I agree with Steven's point. It seems pretty obvious what the intention is, and while it's probably possible to construct examples that are somewhat unclear, 1. The mechanical rule gives an explicit meaning 2. People shouldn't be writing such complex comprehensions, so if the rule doesn't give what they expect, they can always rewrite the code with an explicit (and clearer) loop. me too -- a direct translation to a for loop isn't necessary to understand how it works. -CHB -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception chris.bar...@noaa.gov<mailto:chris.bar...@noaa.gov> _______________________________________________ Python-ideas mailing list Python-ideas@python.org<mailto:Python-ideas@python.org> https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
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