[Python-ideas] iterable.__unpack__ method

Chris Angelico rosuav at gmail.com
Sun Feb 24 15:19:02 CET 2013


On Mon, Feb 25, 2013 at 1:16 AM, Steven D'Aprano <steve at pearwood.info> wrote:
> On 24/02/13 23:59, Chris Angelico wrote:
>>
>> On Sun, Feb 24, 2013 at 10:25 PM, Larry Hastings <larry at hastings.org>
>> wrote:
>>>
>>> Or
>>>
>>>      command, subcommand = next(iterargs), next(iterargs)
>>
>>
>> Err.... is there a language guarantee of the order of evaluation in a
>> tuple, or is this just a "CPython happens to evaluate independent
>> expressions left-to-right"? This is totally broken if the next() calls
>> could be done in either order.
>
> It's a language guarantee.
>
> http://docs.python.org/2/reference/expressions.html#evaluation-order

Ah, so it is. My bad, sorry! In that case, sure, this works. It still
violates DRY though, naming the iterable twice and relying on the
reader noticing that that means "take two off this one". But that's a
much weaker concern.

ChrisA



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