[Python-ideas] for/else statements considered harmful

MRAB python at mrabarnett.plus.com
Thu Jun 7 18:32:45 CEST 2012

On 07/06/2012 16:52, Alice Bevan–McGregor wrote:
> On 2012-06-07 15:30:11 +0000, Mike Meyer said:
>>  Calling it "wrap-up processing" seems likely to cause people to think
>>  about it as meaning "finally". But if the else clause is not executed
>>  if the except clause is (as done by try/except/else), then there's no
>>  longer an easy way to describe it.
>>  It seems like adding an except would change the conditions under which
>>  the else clause is executed (unlike try/except/else), as otherwise
>>  there's no easy way capture the current behavior, where else is
>>  executed whenever there are no chunks left to process. But that kind
>>  of things seems like a way to introduce bugs.
> Well, how about:
>      for<var>  in<iterable>:
>          pass # process each<var>
>      except:  # no arguments!
>          pass # nothing to process
>      else:
>          pass # fell through
>      finally:
>          pass # regardless of break/fallthrough/empty
> Now for loops perfectly match try/except/else/finally!>:D  (Like
> exception handling, finally would be called even with an inner return
> from any of the prior sections.)
Is the "finally" clause really necessary? Is it just the same as putting it
after the loop?

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