Re: Why Python 3?

From	Gregory Ewing <greg.ewing@canterbury.ac.nz>
Newsgroups	comp.lang.python
Subject	Re: Why Python 3?
Date	2014-04-22 10:28 +1200
Message-ID	<brlkdbF8r9iU1@mid.individual.net> (permalink)
References	(8 earlier) <mailman.9373.1397957316.18130.python-list@python.org> <brj1cuFmq1tU1@mid.individual.net> <mailman.9390.1398036251.18130.python-list@python.org> <535493d4$0$29993$c3e8da3$5496439d@news.astraweb.com> <mailman.9397.1398055717.18130.python-list@python.org>

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Chris Angelico wrote:
> All other basic arithmetic operations on two numbers of the same type
> results in another number of that type. ... There's
> just one special case: dividing an integer by an integer yields a
> float, if and only if you use truediv. It sticks out as an exception.

I take your point, but I think this is a case where
practicality beats purity by a large margin. The idea
that arithmetic should always give a result of the same
type is all very nice in theory, but it just isn't
practical where division is concerned.

The reason it doesn't work well is because of the
automatic promotion of ints to floats when they meet
other floats. This leads to a style where people often
use ints to stand for int-valued floats and expect
them to be promoted where necessary.

Things would be different if ints and floats were
completely separate types, like str and bytes, but
that would be extremely inconvenient. I used a language
like that once, and it wasn't a pleasant experience.

-- 
Greg

Thread

Why Python 3? Anthony Papillion <papillion@gmail.com> - 2014-04-18 22:28 -0500
  Re: Why Python 3? Paul Rubin <no.email@nospam.invalid> - 2014-04-18 23:40 -0700
    Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-19 17:34 +1000
      Re: Why Python 3? Roy Smith <roy@panix.com> - 2014-04-19 09:26 -0400
        Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-19 23:42 +1000
        Re: Why Python 3? Albert-Jan Roskam <fomcl@yahoo.com> - 2014-04-19 10:57 -0700
        Re: Why Python 3? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-20 10:07 +0000
    Re: Why Python 3? Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-19 03:25 -0600
      Re: Why Python 3? Marko Rauhamaa <marko@pacujo.net> - 2014-04-19 12:59 +0300
    Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-19 19:37 +1000
      Integer and float division [was Re: Why Python 3?] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-20 11:02 +0000
        Re: Integer and float division [was Re: Why Python 3?] Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-04-20 15:38 +0300
          Re: Integer and float division [was Re: Why Python 3?] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-20 15:09 +0000
        Re: Integer and float division [was Re: Why Python 3?] Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-21 11:44 +1200
    Re: Why Python 3? Terry Reedy <tjreedy@udel.edu> - 2014-04-19 13:23 -0400
      Re: Why Python 3? Paul Rubin <no.email@nospam.invalid> - 2014-04-19 20:25 -0700
        Re: Why Python 3? Ben Finney <ben+python@benfinney.id.au> - 2014-04-20 19:15 +1000
        Re: Why Python 3? Walter Hurry <walterhurry@lavabit.com> - 2014-04-20 23:50 +0000
          Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-21 10:00 +1000
            Re: Why Python 3? HoneyMonster <nobody@someplace.invalid> - 2014-04-21 04:08 +0000
          Re: Why Python 3? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-21 01:11 +0100
    Re: Why Python 3? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-04-19 18:31 +0100
    Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-20 03:53 +1000
    Re: Why Python 3? Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-19 13:58 -0600
    Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-20 06:31 +1000
      Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-20 13:06 +1200
        Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-20 11:28 +1000
          Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-21 10:52 +1200
            Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-21 09:24 +1000
              Re: Why Python 3? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-21 03:43 +0000
                Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-21 14:43 +1000
                Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-22 09:58 +1200
                Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-21 14:48 +1000
                Re: Why Python 3? wxjmfauth@gmail.com - 2014-04-21 02:42 -0700
                Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-22 10:28 +1200
                Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-22 08:43 +1000
                Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-22 18:03 +1200
        Re: Why Python 3? Terry Reedy <tjreedy@udel.edu> - 2014-04-20 00:17 -0400
          Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-21 11:13 +1200
            Re: Why Python 3? Terry Reedy <tjreedy@udel.edu> - 2014-04-20 20:09 -0400
    Re: Why Python 3? Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-19 14:38 -0600
    Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-20 06:53 +1000
      Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-20 13:35 +1200
    Re: Why Python 3? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-20 09:59 +0000
      Unicode in Python Rustom Mody <rustompmody@gmail.com> - 2014-04-21 20:57 -0700
        Re: Unicode in Python Terry Reedy <tjreedy@udel.edu> - 2014-04-22 01:44 -0400
          Re: Unicode in Python Rustom Mody <rustompmody@gmail.com> - 2014-04-21 23:18 -0700
            Re: Unicode in Python Chris Angelico <rosuav@gmail.com> - 2014-04-22 16:32 +1000
        Re: Unicode in Python Steven D'Aprano <steve@pearwood.info> - 2014-04-22 06:11 +0000
          Re: Unicode in Python Rustom Mody <rustompmody@gmail.com> - 2014-04-21 23:30 -0700
            Re: Unicode in Python Chris Angelico <rosuav@gmail.com> - 2014-04-22 16:44 +1000
            Re: Unicode in Python wxjmfauth@gmail.com - 2014-04-22 02:07 -0700
              Re: Unicode in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-22 12:21 +0000
                Re: Unicode in Python wxjmfauth@gmail.com - 2014-04-22 08:28 -0700
        Re: Unicode in Python Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-22 00:31 -0600
          Re: Unicode in Python Rustom Mody <rustompmody@gmail.com> - 2014-04-22 02:23 -0700
          Re: Unicode in Python Rustom Mody <rustompmody@gmail.com> - 2014-04-22 11:09 -0700
    Re: Why Python 3? Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-20 10:22 -0600
      Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-21 11:56 +1200
        Re: Why Python 3? Ian Kelly <ian.g.kelly@gmail.com> - 2014-04-20 18:29 -0600
    Re: Why Python 3? MRAB <python@mrabarnett.plus.com> - 2014-04-20 17:41 +0100
    Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-21 02:46 +1000
      Re: Why Python 3? Roy Smith <roy@panix.com> - 2014-04-20 14:40 -0700
        Re: Why Python 3? Terry Reedy <tjreedy@udel.edu> - 2014-04-20 17:58 -0400
        Re: Why Python 3? Richard Damon <Richard@Damon-Family.org> - 2014-04-20 18:02 -0400
          Re: Why Python 3? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-04-21 12:22 +1200
        Re: Why Python 3? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-04-21 02:13 +0000
  Re: Why Python 3? Steve Hayes <hayesstw@telkomsa.net> - 2014-04-19 13:53 +0200
    Re: Why Python 3? Chris Angelico <rosuav@gmail.com> - 2014-04-19 22:46 +1000
    Re: Why Python 3? Rustom Mody <rustompmody@gmail.com> - 2014-04-19 08:59 -0700
  Re: Why Python 3? Rick Johnson <rantingrickjohnson@gmail.com> - 2014-04-19 07:41 -0700
  Re: Why Python 3? Thomas Lehmann <thomas.lehmann.private@googlemail.com> - 2014-05-06 09:28 -0700

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