PEP308: Yet another syntax proposal

[Harvey Thomas]

Aahz wrote:

> In article <YUP1a.3080$SB2.242 at nwrddc03.gnilink.net>,
> Raymond Hettinger <python at rcn.com> wrote:
> >
> >I suggest:
> >
> >    cond  ??  val1  ||  val2
> 
> +0.5
> 
> I still have yet to see a clear explanation of why short-circuit is
> necessary and therefore iif() unreasonable.
> -- 
> Aahz (aahz at pythoncraft.com)           <*>         

Unless I'm missing the point completely, compare:

if cond:
    x = calc(1, resource_intensive_1())
else:
    x = calc(1, resource_intensive_2())

with

x = calc(1, iif(cond, resource_intensive_1(), resource_intensive_2()))

In the second case both resource_intensive_1() and resource_intensive_2()
are evaluated. There is of course the possibility of undesired side-effects.

You can warn people to not use iif for such cases, but you won't stop it being used wrongly.


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