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Re: l = range(int(1E9))

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From Mark Lawrence <breamoreboy@yahoo.co.uk>
Subject Re: l = range(int(1E9))
Date Sat, 02 May 2015 16:40:44 +0100
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On 02/05/2015 16:26, BartC wrote:
> On 30/04/2015 18:20, Ben Finney wrote:
>> Jon Ribbens <jon+usenet@unequivocal.co.uk> writes:
>
>>> If you use xrange() instead of range() then you will get an iterator
>>> which will return each of the numbers in turn without any need to
>>> create an enormous list of all of them.
>>
>> If you use Python 3 instead of the obsolescent Python 2, the ‘range’
>> callable has this sensible behaviour by default.
>
> When I first looked at Python 20 or so years ago this seemed to be the
> standard way of writing a for-loop:
>
> for i in range(N):
>     ....
>
> I remember being completely astonished at the time that 'range' actually
> created a list of values from 0 to N-1.
>
> Python was already known to be slow yet it deliberately crippled itself
> by using just about the slowest method imaginable of executing a simple
> iterative loop? By first creating a list of a million objects!
>
> And sometimes you weren't even interested in the values but just wanted
> to execute something N times so it was a wasted effort.
>
> That was eventually fixed with xrange, but why do it like that in the
> first place?
>
> (At the time, I was creating bytecode languages as part of the
> applications I was writing. An empty for-loop executed just one bytecode
> per iteration, and it was also the fastest bytecode instruction. An
> empty for-loop executed three Python bytecodes per iteration last time I
> looked. It seems that Python used to like making a rod for its own back.)
>

I first started maybe 14 years ago and the standard way of writing a for 
loop was, and still is:-

for item in items:

When did this change, or has it always been this way and you were simply 
using an idiom from other languages?

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence

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Thread

l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 18:06 +0200
  Re: l = range(int(1E9)) Grant Edwards <invalid@invalid.invalid> - 2015-04-30 16:33 +0000
    Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 19:26 +0200
      Re: l = range(int(1E9)) Ben Finney <ben+python@benfinney.id.au> - 2015-05-01 03:41 +1000
        Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 20:44 +0200
    Re: l = range(int(1E9)) Roel Schroeven <roel@roelschroeven.net> - 2015-04-30 21:40 +0200
  Re: l = range(int(1E9)) Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-04-30 16:55 +0000
    Re: l = range(int(1E9)) Ben Finney <ben+python@benfinney.id.au> - 2015-05-01 03:20 +1000
      Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-01 15:20 +1000
        Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 08:08 +0200
      Re: l = range(int(1E9)) BartC <bc@freeuk.com> - 2015-05-02 16:26 +0100
        Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-02 16:40 +0100
          Re: l = range(int(1E9)) BartC <bc@freeuk.com> - 2015-05-02 17:17 +0100
            Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-02 17:39 +0100
              Re: l = range(int(1E9)) BartC <bc@freeuk.com> - 2015-05-02 19:34 +0100
                Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-02 20:15 +0100
                Re: l = range(int(1E9)) Marko Rauhamaa <marko@pacujo.net> - 2015-05-02 22:26 +0300
                Re: l = range(int(1E9)) BartC <bc@freeuk.com> - 2015-05-02 20:51 +0100
                Re: l = range(int(1E9)) Joel Goldstick <joel.goldstick@gmail.com> - 2015-05-02 17:21 -0400
                Re: l = range(int(1E9)) Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-02 15:31 -0600
                Re: l = range(int(1E9)) Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-05-02 21:40 +0000
                Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-02 23:26 +0100
                Re: l = range(int(1E9)) BartC <bc@freeuk.com> - 2015-05-02 23:33 +0100
                Re: l = range(int(1E9)) Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-05-03 00:13 +0000
                Re: l = range(int(1E9)) Michael Torrie <torriem@gmail.com> - 2015-05-02 20:07 -0600
                Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-03 03:16 +0100
                Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-03 21:16 +1000
                Re: l = range(int(1E9)) Chris Angelico <rosuav@gmail.com> - 2015-05-03 21:30 +1000
                Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-03 19:36 +0100
                Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-03 21:15 +1000
                Re: l = range(int(1E9)) Chris Angelico <rosuav@gmail.com> - 2015-05-03 21:29 +1000
                Re: l = range(int(1E9)) Terry Reedy <tjreedy@udel.edu> - 2015-05-02 19:26 -0400
                Re: l = range(int(1E9)) Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-05-03 00:01 +0000
                Re: l = range(int(1E9)) Terry Reedy <tjreedy@udel.edu> - 2015-05-02 23:18 -0400
                Re: l = range(int(1E9)) Jon Ribbens <jon+usenet@unequivocal.co.uk> - 2015-05-03 03:40 +0000
                Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-03 21:05 +1000
                Re: l = range(int(1E9)) Terry Reedy <tjreedy@udel.edu> - 2015-05-02 19:51 -0400
                Re: l = range(int(1E9)) Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-02 22:51 -0600
                Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-03 21:21 +1000
                Re: l = range(int(1E9)) Marko Rauhamaa <marko@pacujo.net> - 2015-05-02 22:15 +0300
            Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-03 20:32 +1000
              Re: l = range(int(1E9)) Chris Angelico <rosuav@gmail.com> - 2015-05-03 20:59 +1000
        Re: l = range(int(1E9)) Terry Reedy <tjreedy@udel.edu> - 2015-05-02 18:41 -0400
    Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 19:28 +0200
  Re: l = range(int(1E9)) Terry Reedy <tjreedy@udel.edu> - 2015-04-30 13:02 -0400
  Re: l = range(int(1E9)) Gary Herron <gherron@digipen.edu> - 2015-04-30 10:05 -0700
    Re: l = range(int(1E9)) Rob Gaddi <rgaddi@technologyhighland.invalid> - 2015-04-30 17:12 +0000
      Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 20:50 +0200
        Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-04-30 21:53 +0100
          Re: l = range(int(1E9)) ElChino <elchino@cnn.cn> - 2015-04-30 23:23 +0200
            Re: l = range(int(1E9)) Chris Angelico <rosuav@gmail.com> - 2015-05-01 08:45 +1000
              Re: l = range(int(1E9)) ElChino <elchino@cnn.cn> - 2015-05-01 01:03 +0200
            Re: l = range(int(1E9)) Ben Finney <ben+python@benfinney.id.au> - 2015-05-01 09:12 +1000
              Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 07:04 +0200
                Re: l = range(int(1E9)) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-05-01 13:15 +0200
                Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 14:22 +0200
                Re: l = range(int(1E9)) Terry Reedy <tjreedy@udel.edu> - 2015-05-01 22:00 -0400
            Use ‘python2’ or ‘python3’, explicit is better than implicit  (was: l = range(int(1E9))) Ben Finney <ben+python@benfinney.id.au> - 2015-05-01 09:19 +1000
              Re: Use 'python2' or 'python3', explicit is better than implicit  (was: l = range(int(1E9))) Rustom Mody <rustompmody@gmail.com> - 2015-04-30 19:24 -0700
            Re: l = range(int(1E9)) Chris Angelico <rosuav@gmail.com> - 2015-05-01 09:23 +1000
          Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 06:19 +0200
            Re: l = range(int(1E9)) Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-05-01 05:41 +0100
            Re: l = range(int(1E9)) Michael Torrie <torriem@gmail.com> - 2015-05-01 07:25 -0600
              Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 16:12 +0200
  Re: l = range(int(1E9)) Gisle Vanem <gvanem@yahoo.no> - 2015-04-30 20:23 +0200
    Re: l = range(int(1E9)) alister <alister.nospam.ware@ntlworld.com> - 2015-04-30 18:48 +0000
      Re: l = range(int(1E9)) Dave Angel <davea@davea.name> - 2015-04-30 14:59 -0400
        Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 22:18 +0200
          Re: l = range(int(1E9)) Tim Chase <python.list@tim.thechases.com> - 2015-04-30 16:41 -0500
            Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 07:19 +0200
  Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-01 14:42 +1000
    Re: l = range(int(1E9)) Cecil Westerhof <Cecil@decebal.nl> - 2015-05-01 07:13 +0200
    Re: l = range(int(1E9)) Tony the Tiger <tony@tiger.invalid> - 2015-05-02 21:28 +0000
      Re: l = range(int(1E9)) Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-02 15:32 -0600
      Re: l = range(int(1E9)) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-03 20:56 +1000

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