Re: Why Python 3?

References	<mailman.9344.1397878113.18130.python-list@python.org> <7x8ur1esa5.fsf@ruckus.brouhaha.com>
Date	2014-04-19 17:34 +1000
Subject	Re: Why Python 3?
From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.9352.1397892885.18130.python-list@python.org> (permalink)

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On Sat, Apr 19, 2014 at 4:40 PM, Paul Rubin <no.email@nospam.invalid> wrote:
> If you're starting a new project and you get to choose between 2 and 3,
> other things equal I'd say use 3.  I've kept using 2 basically because
> it's the path of least resistance.  I'm somewhat following the 3
> situation and of course I'd use 3 if I were doing something that
> benefited from it, but so far it hasn't been an issue.
>
> Eventually the main Linux distros will include 3 instead of 2 by
> default, and we'll probably see more migration then.  Right now I type
> "python" and get 2, so I use it.

Several of the main distros are already including Python 3 by default
(eg Ubuntu), but when you type "python", you still get Python 2, for
reasons of compatibility. (See PEP 394.) As long as you set your
shebang to say python3, it'll work just fine.

I strongly recommend going for Python 3 unless something actually
stops you from doing so. If you absolutely must use Python 2, try to
aim for a minimum of 2.6 or 2.7, and start your program with this
line:

from __future__ import print_function, unicode_literals, division

That'll make Python 2.6/2.7 behave like Python 3.x in three ways:
firstly, "print" will be a function instead of a statement (and it's
more powerful than the statement form, as well as being more
flexible); secondly, quoted strings will be Unicode strings, not byte
strings (that'll help you to start thinking about what's bytes and
what's text, which is an important distinction in Python 3); and
thirdly, though less important than the others, the division of two
integers will result in a floating point, not an integer. I personally
think the last one was a mistake on Python 3's part (why bless float
specifically? what if you're working with integers and
decimal.Decimals?), but if you're going to move to Python 3, you may
as well have your code start working that way, so you get used to
typing // to divide integers and get an integer (floor division).

But if you possibly can, aim for Python 3. Every new version adds
features, and new versions within the 3.x line break very little
(generally only what would have been working with a bug anyway, like
narrow Unicode builds of 3.2 becoming universal on 3.3). If you aim
for 3.2 today, and tomorrow try to run your code on 3.4, chances are
it'll work. The main thing is, know what's a text string and what's a
string of bytes; that's critical in 3.x, but not in 2.x. Force
yourself to think about that, and your code will be more reliable -
regardless of even what language you write it in.

ChrisA

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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