[Python-ideas] Deterministic iterator cleanup

[Paul Moore]

On 21 October 2016 at 21:59, Chris Barker <chris.barker at noaa.gov> wrote:
>> So (it seems to
>> me) that you're talking about changing the behaviour of for-loops to
>> suit only a small proportion of cases: maybe 10% of 10%.
>
>
> I don't see what the big overhead is here. for loops would get a new
> feature, but it would only be used by the objects that chose to implement
> it. So no huge change.

But the point is that the feature *would* affect people who don't need
it. That's what I'm struggling to understand. I keep hearing "most
code won't be affected", but then discussions about how we ensure that
people are warned of where they need to add preserve() to their
existing code to get the behaviour they already have. (And, of course,
they need to add an "if we're on older pythons, define a no-op version
of preserve() backward compatibility wrapper if they want their code
to work cross version). I genuinely expect preserve() to pretty much
instantly appear on people's lists of "python warts", and that bothers
me.

But I'm reaching the point where I'm just saying the same things over
and over, so I'll bow out of this discussion now. I remain confused,
but I'm going to have to trust that the people who have got a handle
on the issue have understood the point I'm making, and have it
covered.

Paul