[Python-ideas] 'where' statement in Python?

[Andrey Popp]

Also, what about some alternative for workaround the following:

> Out of Order Execution: the where clause makes execution jump around a little strangely, as
> the body of the where clause is executed before the simple statement in the clause header. The
> closest any other part of Python comes to this before is the out of order evaluation in
> conditional expressions.

result = let:
   a = retrieve_a()
   b = retreive_b()
in:
   a*a + b*b

On Tue, Jul 20, 2010 at 6:57 PM, Andrey Popp <8mayday at gmail.com> wrote:
> Hello,
>
> PEP-3150 is awesome, just a small addition — why not to allow
> one-liners `where`s:
>
>    a = (b, b) where b = 43
>
> And that also make sense for generator/list/set/dict comprehensions:
>
>    mylist = [y for y in another_list if y < 5 where y = f(x)]
>
> On Tue, Jul 20, 2010 at 5:27 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
>> On Tue, Jul 20, 2010 at 3:29 PM, Stephen J. Turnbull <stephen at xemacs.org> wrote:
>>> We just had a long thread about this.
>>>
>>> http://mail.python.org/pipermail/python-ideas/2010-June/007476.html
>>>
>>> The sentiment was about -0 to -0.5 on the idea in general, although a
>>> couple of people with experience in implementing Python syntax
>>> expressed sympathy for it.
>>
>> For the record, I am personally +1 on the idea (otherwise I wouldn't
>> have put so much thought into it over the years). It's just a *lot*
>> harder to define complete and consistent semantics for the concept
>> than people often realise.
>>
>> However, having the question come up twice within the last month
>> finally inspired me to write the current status of the topic down in a
>> deferred PEP: http://www.python.org/dev/peps/pep-3150/
>>
>> Cheers,
>> Nick.
>>
>> --
>> Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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>
>
>
> --
> Andrey Popp
>
> phone: +7 911 740 24 91
> e-mail: 8mayday at gmail.com
>



-- 
Andrey Popp

phone: +7 911 740 24 91
e-mail: 8mayday at gmail.com