[Python-ideas] Nudging beginners towards a more accurate mental model for loop else clauses

[Rob Cliffe]

On 08/06/2012 12:53, Nick Coghlan wrote:
> On Fri, Jun 8, 2012 at 7:44 PM, Rob Cliffe<rob.cliffe at btinternet.com>  wrote:
>> I think a better scheme would be to have more meaningful keywords or
>> keyword-combinations, e.g.
>>
>> for x in iterable:
>>     # do stuff
>> ifempty:  #  or perhaps ifnoiter: (also applicable to while loops)
>>     # do stuff
>> #ifbreak:
>>     # do stuff
>> #ifnobreak:
>>     # do stuff
>>
>> which would give all the flexibility while making it reasonably clear what
>> was happening.
> The way to be clear would actually be to drop the feature altogether
> (as Guido has noted in the past). Then TOOWTDI becomes:
>
>      x = _no_data = object()
>      result = _not_found = object()
>      for x in iterable:
>          if acceptable(x):
>              result = x
>              break
>      if x is _no_data:
>          # No data!
>      if result is _not_found:
>          # Nothing interesting!
>      # Found a result, process it
>
> That's never going to happen in Python though, due to backwards
> compatibility requirements.
>
> FWIW, I wrote an essay summarising some of the thoughts presented in
> these threads:
> http://readthedocs.org/docs/ncoghlan_devs-python-notes/en/latest/python_concepts/break_else.html
>
> Cheers,
> Nick.
>
Fair enough, but I think my more compact versions are more readable.
Rob