Extension of while syntax

[Mark Lawrence]

On 12/12/2014 02:21, Nelson Crosby wrote:
> I was thinking a bit about the following pattern:
>
> value = get_some_value()
> while value in undesired_values:
>      value = get_some_value()
>
> I've always hated code that looks like this. Partly due to the repetition, but partly also due to the fact that without being able to immediately recognise this pattern, it isn't very readable.
>
> Python already has one-line syntaxes (e.g. list comprehensions), I was wondering what people thought about a similar thing with while. It might look something like:
>
> value = get_some_value() while value in undesired_values()
>
> Perhaps not this exact syntax though, as the parser might try to do `value = (get_some_value() while...)` instead of `(value = get_some_value) while...`.
>
> Other languages have features which allow something to look slightly less like this pattern, e.g. Java:
>
> SomeType value;
> while ((/* The assignment */ value = getSomeValue()) /* Compare */ == undesired_value) {}
>
> Granted, this isn't exactly tidy, but it's a little more DRY and, IMO, preferable.
>
> What are other's thoughts on this?
>

It won't happen as different format loops have been discussed and 
rejected umpteen times over the last 20 odd years, mainly because the 
code can be restructured using break as others have already pointed out. 
  Unless of course you fork Python, joining others working on variants 
such as Python 2.8 or RickedPython :)

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence