seeking deeper (language theory) reason behind Python design choice

[Ian Kelly]

On Thu, May 10, 2018 at 11:17 PM, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> To answer your question from a later post:
>
>     In what way does "while True" in the general case pretend
>     to be an infinite loop?
>
> It doesn't *pretend* to be an infinite loop. It *is* an infinite loop
> which breaks out early.
>
> I realise that all infinite loops end up breaking out early, even if it's
> only when you power-cycle the device. But code ought to match intent, and
> "while condition which can never be false" shouts from the mountain tops
> that it is an infinite loop. The simpler the condition, the more loudly
> it shouts, and you can't get simpler than True.
>
> (The one thing that beats "while True" as an indicator of an infinite
> loop is the old Hypertalk syntax "repeat forever".)

How about the asyncio event loop's run_forever and run_until_complete
methods? run_forever also implies an infinite loop, except that you
can stop the event loop at any time. The other choice,
run_until_complete, requires that you already know when you want to
stop when you call it. Another way of looking at it, run_forever is
like a while loop and run_until_complete is like a for loop.

So if you know you want to stop the loop at some point, but you don't
know when, what do you do to express your intent?

> and if we came across it in real life, we'd surely question the sanity of
> the developer who wrote it. Why should while loops be any different?
>
>     while True:
>         if not condition: break  # equivalent to GOTO 99
>         block
>     LABEL 99
>
> I understand that *today*, using existing Python syntax, there is
> sometimes no avoiding that (except, possibly, with something worse). I
> get that. But if we had the choice to move the condition into the while
> condition, we ought to take it.

This is a straw man. As I already replied to Chris, this is not the
type of while True I've been arguing for. Obviously in this case the
condition should be moved into the while statement.