[Python-ideas] Is this PEP-able? for X in ListY while conditionZ:
Ned Batchelder
ned at nedbatchelder.com
Tue Jun 25 23:15:47 CEST 2013
On 6/25/2013 4:58 PM, jimjhb at aol.com wrote:
> I saw your thread. Thank you for summarizing the result! It looks
> like the best alternative is itertools.takewhile, but I don't like
> it.... :(
>
Ugh! The best alternative is "break." The people advocating not using
break are doing so for "readability" reasons. I would be very surprised
if they thought takewhile was more readable than a break statement.
Slavishly following mindless rules is not the way to write good
programs, and it isn't the way to teach people to write good programs.
Resist! :)
--Ned.
> -Jim
>
> -----Original Message-----
> From: Wolfgang Maier <wolfgang.maier at biologie.uni-freiburg.de>
> To: python-ideas <python-ideas at python.org>
> Sent: Tue, Jun 25, 2013 4:51 pm
> Subject: Re: [Python-ideas] Is this PEP-able? for X in ListY while
> conditionZ:
>
> Hi,
> I suggested the very same 'while in a comprehension/generator expression'
> back in January:
> http://mail.python.org/pipermail/python-ideas/2013-January/018969.html
>
> There were many very useful responses suggesting alternative syntax (that
> I'm using now).
> The proposal itself was dismissed with the logic that comprehensions can
> currently be translated directly into explicit for loops, e.g.:
>
> [x for x in items if x!=0]
>
> equals:
>
> result=[]
> for x in items:
> if x!=0:
> result.append(x)
>
> This equivalence is considered *very* important and the while statement
> would break it:
>
> [x for x in items while x>0]
>
> does *not* translate into:
>
> for x in item:
> while x>0:
> result.append(x)
>
> So, as long as you can't come up with syntax that translates properly,
> there's no chance of getting it accepted.
>
> Best,
> Wolfgang
>
>
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