[Python-ideas] 'where' statement in Python? (original) (raw)

Andrey Popp 8mayday at gmail.com
Tue Jul 20 17:01:39 CEST 2010

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: aa + bb

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 wheres:  a = (b, b) where b = 43 And that also make sense for generator/list/set/dict comprehensions:  mylist = [y for y in anotherlist 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

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