(trying with direct reply this time) > Why do you do this? What's the requirement for delaying evaluation of the > condition?
Thanks for challenging my poorly chosen examples :) The primary requirement is about *catching* unwanted/uncontrolled/heterogenous exceptions happening in the underlying functions that are combined together to provide the validation means, so as to provide a uniform/consistent outcome however diverse the underlying functions are (they can return booleans or raise exceptions, or both). In your proposal, if 'is_foo_compliant' raises an exception, it will not be caught by 'assert_valid', therefore the ValidationError will not be raised. So this is not what I want as an application developer. -- Sylvain -----Message d'origine----- De : Paul Moore [mailto:p.f.mo...@gmail.com] Envoyé : mardi 16 janvier 2018 18:01 À : Sylvain MARIE <sylvain.ma...@schneider-electric.com> Cc : Python-Ideas <python-ideas@python.org> Objet : Re: [Python-ideas] Repurpose `assert' into a general-purpose check I fixed the reply-to this time, looks like you're still getting messed up by Google Groups. On 16 January 2018 at 16:25, smarie <sylvain.ma...@schneider-electric.com> wrote: > Let's consider this example where users want to define on-the-fly one > of the validation functions, and combine it with another with a 'or': > > assert_valid('surface', surf, or_(lambda x: (x >= 0) & (x < > 10000), is_foo_compliant), help_msg="surface should be 0=<x<10000 or > foo compliant") > > How ugly for something so simple ! I tried to make it slightly more > compact by developping a mini lambda syntax but it obviously makes it slower. Why do you do this? What's the requirement for delaying evaluation of the condition? A validate statement in Python wouldn't be any better able to do that, so it'd be just as ugly with a statement. There's no reason I can see why I'd ever need delayed evaluation, so what's wrong with just assert_valid(0 <= surf < 10000 and is_foo_compliant(surf), help_msg="surface should be 0=<x<10000 or foo compliant") > There are three reasons why having a 'validate' statement would > improve > this: > > * no more parenthesis: more elegant and readable > * inline use of python (1): no more use of lambda or mini_lambda, no > performance overhead > * inline use of python (2): composition would not require custom > function composition operators such as 'or_' (above) or mini-lambda > composition anymore, it could be built-in in any language element used > after <validate> > > resulting in > > validate (surf >= 0) & (surf < 10000) or > is_foo_compliant(surf), "surface should be 0=<x<10000 or foo compliant" So how will that work any differently than the function version I gave above? In terms of the language syntax, it would just be validate EXPR, EXPR and the first EXPR will be evaluated as a boolean, and if it's false an exception will be raised with the second expression as the message. There's no delayed evaluation involved, so a function would work exactly the same. > > (I removed the variable name alias 'surface' since I don't know if it > should remain or not) > > Elegant, isn't it ? No more so than my function version, but yes far more so than yours... Paul ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
