[Python-Dev] PEP 548: More Flexible Loop Control

[R. David Murray]

On Wed, 06 Sep 2017 15:05:51 +1000, Chris Angelico <rosuav at gmail.com> wrote:
> On Wed, Sep 6, 2017 at 10:11 AM, R. David Murray <rdmurray at bitdance.com> wrote:
> > I've written a PEP proposing a small enhancement to the Python loop
> > control statements.  Short version: here's what feels to me like a
> > Pythonic way to spell "repeat until":
> >
> >     while:
> >         <do stuff>
> >         break if <done condition>
> >
> > The PEP goes into some detail on why this feels like a readability
> > improvement in the more general case, with examples taken from
> > the standard library:
> >
> >      https://www.python.org/dev/peps/pep-0548/
> 
> Is "break if" legal in loops that have their own conditions as well,
> or only in a bare "while:" loop? For instance, is this valid?
> 
> while not found_the_thing_we_want:
>     data = sock.read()
>     break if not data
>     process(data)

Yes.

> Or this, which uses the condition purely as a descriptor:
> 
> while "moar socket data":
>     data = sock.read()
>     break if not data
>     process(data)

Yes.

> Also - shouldn't this be being discussed first on python-ideas?

Yep, you are absolutely right.  Someone has told me I also missed
a related discussion on python-ideas in my searching for prior
discussions.  (I haven't looked for it yet...)

I'll blame jet lag :)

--David