On 29 April 2015 at 19:42, Sergey B Kirpichev <report@bugs.python.org> wrote:
>> It's a common computer science technique
>
> Could you provide any language that avoid this optimization?
>
> Here is Perl 5:
> http://perl5.git.perl.org/perl.git/blob/HEAD:/pp_sort.c#l367
>
> (third example)

But that's a sort without a key. In Perl you do a key sort via:

@sorted = map  { $_->[0] }
          sort { $a->[1] <=> $b->[1] } # use numeric comparison
          map  { [$_, length($_)] }    # calculate the length of the string
               @unsorted;

(From http://en.wikipedia.org/wiki/Schwartzian_transform). That
computes the keys first, and would compute the key for a list of
length 1, just like Python does. It's just that Python bundles that
whole construct into the "key=" argument.

But it's your choice - if this is a big enough deal to put you off
Python, I guess no-one will be able to stop you. The fact of the
matter is that what Python does is documented behaviour, and the
benefit (small) isn't worth the cost of making a change (which would
only be in Python 3.5 and later anyway, as it's a backward
incompatible change, not a bug fix).