[Python-Dev] PEP 340: Breaking out.

[Paul Moore]

On 5/4/05, Alex Martelli <aleaxit at yahoo.com> wrote:
> 
> On May 4, 2005, at 01:57, Paul Moore wrote:
> >
> > I can't think of a reasonable condition which wouldn't involve reading
> > the file - which either involves an inner loop (and we already can't
> > break out of two loops, so the third one implied by the opening block
> > makes things no worse), or needs the whole file reading (which can be
> 
> Looking for a file with a certain magicnumber in its 1st two bytes...?
> 
> for name in filenames:
>     opening(name) as f:
>         if f.read(2) == 0xFEB0: break
> 
> This does seem to make real-life sense to me...

Yes, that'd do. I can't say I think it would be common, but it's a
valid case. And the workaround is the usual messy flag variable:

for name in filenames:
    found = False
    opening(name) as f:
        if f.read(2) == 0xFEB0: found = True
    if found: break

Yuk.

Paul.