[Python-ideas] if condition: break idiom

[Ron Adam]

Carl Johnson wrote:
> Slightly OT, but I think 'break' and 'continue' should be replaced with 
> 'raise Break' and 'raise Continue' in Python 4000, just as we 'raise 
> StopIteration' in generators today. This would be handy, because you 
> could use it in functions called by a list comprehension:
> 
> def while(x):
>     if x > 10:
>         raise Break
>     else:
>         return x
> 
> [while(x) for x in range(20)]  #produces [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
> 
> Right now, you can do something this with list(generator expression) by 
> raising StopIteration, but it is considered a hack, and it doesn't work 
> with list comprehensions.

Maybe break should raise a StopIteration and continue should raise 
NextIteration?

What would be the effect on performance to for and while loops?

Ron