[Python-Dev] PEP 340: Deterministic Finalisation (new PEP draft, either a competitor or update to PEP 340)

[Nick Coghlan]

Raymond Hettinger wrote:
> [Nick Coghlan]
> 
>>The number of good use cases for a looping block statement currently
>>stands at
>>exactly 1 (auto_retry). Every other use case suggested (locking,
> 
> opening,
> 
>>suppressing, etc) involves factoring out try statement boiler plate
> 
> that
> 
>>is far
>>easier to comprehend with a single pass user defined statement. 
> 
> 
> I would like to offer up one additional use case, eliminating redundant
> code in a do-while construct:
> 
> 
> def do_while(cond_func):
>     yield
>     while cond_func():
>         yield
> 
> block do_while(lambda: a>b):
>     <sequence of actions affecting a and b>

Nice example, but it doesn't need to intercept exceptions the way auto_retry 
does. Accordingly, a 'for' loop which makes [VAR in] optional would do the job 
just fine:

   for do_while(lambda: a>b):
       <do it>

Even today, the following works:

   def do_while(cond_func):
       yield None
       while cond_func():
           yield None

   for _ in do_while(lambda: a>b):
       <do it>

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
---------------------------------------------------------------
             http://boredomandlaziness.blogspot.com