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Tue May 27 12:01:35 CEST 2014 · http://mail.python.org/pipermail/python-dev/2014-May/134643.html

On 27.05.2014 11:05, Chris Angelico wrote:
> On Tue, May 27, 2014 at 6:58 PM, Serhiy Storchaka <storchaka at gmail.com> wrote:
>> 26.05.14 10:59, raymond.hettinger написав(ла):
>>>
>>> +        result = [(elem, i) for i, elem in zip(range(n), it)]
>>
>>
>> Perhaps it is worth to add simple comment explaining why this is not
>> equivalent to just list(zip(it, range(n))). Otherwise it can be
>> unintentionally "optimized" in future.
>>
> 
> Where is the difference? I'm very much puzzled now. My first thought
> was based on differing-length iterables in zip, but the docs say it
> stops at the shortest of its args.

Nice puzzle. (elem, i) is not (i, elem), though. Thats really hard to
see when not looking at it closely.

> 
> ChrisA
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Showing content from http://mail.python.org/pipermail/python-dev/2014-May/134643.html below:

[Python-Dev] cpython: Minor clean-ups for heapq.