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Message-Id: <1536878.qVoOGUtdWV@PointedEars.de>
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Reply-To: Thomas 'PointedEars' Lahn <usenet@PointedEars.de>
Organization: PointedEars Software (PES)
Date: Thu, 23 Jun 2011 12:23:35 +0200
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Subject: Re: writable iterators?
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[Sorry for over-quoting, I am not sure how to trim this properly]

Steven D'Aprano wrote:

> On Thu, 23 Jun 2011 09:30 am Thomas 'PointedEars' Lahn wrote:
>> Mel wrote:
>>> Steven D'Aprano wrote:
>>>> I *guess* that what you mean by "writable iterators" is that rebinding
>>>> e should change seq in place, i.e. you would expect that seq should now
>>>> equal [42, 42]. Is that what you mean? It's not clear.
>>>> 
>>>> Fortunately, that's not how it works, and far from being a
>>>> "limitation", it would be *disastrous* if iterables worked that way. I
>>>> can't imagine how many bugs would occur from people reassigning to the
>>>> loop variable, forgetting that it had a side-effect of also reassigning
>>>> to the iterable. Fortunately, Python is not that badly designed.
>>> 
>>> And for an iterator like
>>> 
>>> def things():
>>>     yield 1
>>>     yield 11
>>>     yield 4
>>>     yield 9
>>> 
>>> I don't know what it could even mean.
>> 
>> <http://docs.python.org/reference/simple_stmts.html#the-yield-statement>
>> 
>> You could have tried to debug.
> 
> I think you have missed the point of Mel's comment. He knows what the
> yield statement does. He doesn't know what it would mean to "write to" an
> iterator like things().
> 
> Neither do I.

AIUI the OP is referring to write accesses to the iteration variable
(for want of a better term), not being aware what iterators are.

-- 
PointedEars

Bitte keine Kopien per E-Mail. / Please do not Cc: me.