[Python-ideas] Break multiple loop levels

[Ronie Martinez]

What if labels are placed in comments beside the loops, like how type is,
at least, being used by analyzers?

for x in range(100):  # label: outer
    for y in range(3):   # label: inner


On Sun, May 12, 2019 at 5:45 PM Steven D'Aprano <steve at pearwood.info> wrote:

> On Sun, May 12, 2019 at 11:16:21AM +0200, Oleg Broytman wrote:
> > On Sun, May 12, 2019 at 01:36:28AM -0700, Elias Tarhini <
> eltrhn at gmail.com> wrote:
> > > If I may propose `break n` as a replacement for the original message's
> > > `break break ... break`, where n>0 is the number of contiguous loops to
> > > break out of and `break 1` is synonymous with `break`. Seems easier on
> my
> > > eyes/noggin than counting out the individual `break` statements.
> >
> >    This is very much error-prone because on any refactoring (increasing
> > or decreasing the number of loop levels) one must increase/decrease all
> > numbers in internal loops.
> >
> >    Labels are at least stable.
>
> Indeed.
>
> Go has labels for loops:
>
>     Label:
>         for { ...
>               break Label
>             }
>
> as does Rust:
>
>     'label: while condition:
>            {
>             ...
>             break label
>             }
>
> We can't use the same syntax in Python, but we might write it like this:
>
>     @label while condition:
>         block
>         break label
>
> and similar with for loops:
>
>     @outer for x in range(100):
>         @inner for y in range(3):
>             if x == y == 1: break  # like ``break inner``
>             if x == y == 2: break outer
>             print(x, y)
>         # break inner jumps to here
>     # break outer jumps to here
>
>
> --
> Steven
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