[Python-Dev] PEP 340: Breaking out.

[Nick Coghlan]

Alex Martelli wrote:
> 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...

Also consider the vast semantic differences between:

   locking(lock):
       for item in items:
           if can_handle(item): break

   for item in items:
       locking(lock):
           if can_handle(item): break


Instead of simply acquiring and releasing the lock on each iteration as one 
might expect, moving to the latter version *also* causes every item to be 
checked, instead of only items up to the first one that can be handled. The 
break magically becomes meaningless. How does this even come close to executable 
pseudocode?

I also think another factor is that currently, instead of doing try/finally's in 
loops, there is a tendency to push the try/finally into a function, then call 
that function inside the loop. The introduction of block statements means that a 
number of those inner functions are likely to be handled as block statements 
instead - with the above highly confusing result.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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