[Python-ideas] Break multiple loop levels

[haael]

How about doing it pythonic way then, "everything is a hack on a symbol 
table".

Let normal loops remain normal loops.

Let's introduce a special construction:

 > for x in iterator as loop_control_object:
 >     loop_body(loop_control_object)


The iterator in the loop would be wrapped inside another iterator that 
would yield everything as the original iterator, but it would also be 
controllable through loop_control_object.

Sample implementation:

 > def make_control_object(iterator):
 >    control_object = ControlObject()
 >    control_object.running = True
 >    def breakable_iterator():
 >        for x in iterator:
 >            yield x
 >            if not control_object.running:
 >                return
 >    return breakable_iterator(), control_object

The control object could have methods that allow sophisticated loop 
control, such as breaking, continuing, injecting exceptions, counting 
iterations, skipping etc.

The keywords 'break loop_control_object' and 'continue 
loop_control_object' could be simply implemented as:

 > loop_control_object.do_break()



> On Sun, May 12, 2019, 5:36 PM Paul Moore <p.f.moore at gmail.com 
> <mailto:p.f.moore at gmail.com>> wrote:
> 
>     On Sun, 12 May 2019 at 21:06, David Mertz <mertz at gnosis.cx
>     <mailto:mertz at gnosis.cx>> wrote:
>      > I thought of 'as' initially, and it reads well as English. But it
>     felt to me like the meaning was too different from the other
>     meanings of 'as' in Python. I might be persuaded otherwise.
> 
>     If you think in terms of "named loops" rather than "labels", "as"
>     makes a lot more sense.
> 
> 
> Every name created with 'as' currently is a regular Python object, with 
> a memory address, and some methods, that can participate in comparison 
> (at least equality), that has a type, can be passed as a function 
> argument, etc. Actually, all that is true of EVERY name in Python other 
> than keywords.
> 
> It seems like none of this would be true of a loop name/label. Hence my 
> first thought that a different way of introducing the word is more 
> clear... Maybe we can just prefix lines with labels instead, and add a 
> 'goto' command :-)
> 
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