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Groups > comp.lang.python > #68620

Re: running python 2 vs 3

From Ned Batchelder <ned@nedbatchelder.com>
Subject Re: running python 2 vs 3
Date 2014-03-20 16:53 -0400
References (1 earlier) <87ob10nbeh.fsf@elektro.pacujo.net> <532B4750.2090006@yahoo.com> <87eh1wpr96.fsf@elektro.pacujo.net> <mailman.8316.1395347407.18130.python-list@python.org> <8738icppoe.fsf@elektro.pacujo.net>
Newsgroups comp.lang.python
Message-ID <mailman.8320.1395348816.18130.python-list@python.org> (permalink)

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On 3/20/14 4:42 PM, Marko Rauhamaa wrote:
> Ned Batchelder <ned@nedbatchelder.com>:
>
>> Plenty of people have adopted a dual-support strategy, with one code
>> base that supports both Python 2 and Python 3. The six module can help
>> a great deal with this.
>
> I wonder how easy the resulting code is to the eyes and how easy it is
> for the casual maintainer to accidentally break the delicate balance. In
> a word, I wouldn't go there. Stay with Python2 as long as you must and
> then, migrate and leave it behind.

This is fine advice for applications, but tools, libraries, and 
frameworks may want to support more than one version at the same time.

It's an extreme case, but the latest released version of coverage.py 
supports Python 2.3 through 3.3 with one code base.  To do it, there's a 
compatibility layer (akin to six).  Then you stay away from features 
that aren't available on all versions.  In a few places, you might need 
to have version checks, and the code can get a little idiomatic to 
continue to work.

It's a tradeoff: you have to decide for yourself whether the effort is 
worth the benefit.  I was glad to be able to drop support for 2.3, 2.4, 
and 2.5, and now only support 2.6-3.4 in coverage.py.

>
>
> Marko
>


-- 
Ned Batchelder, http://nedbatchelder.com

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Thread

running python 2 vs 3 notbob <notbob@nothome.com> - 2014-03-20 14:58 +0000
  Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 17:21 +0200
    Re: running python 2 vs 3 notbob <notbob@nothome.com> - 2014-03-20 16:00 +0000
      Re: running python 2 vs 3 Zachary Ware <zachary.ware+pylist@gmail.com> - 2014-03-20 11:14 -0500
        Re: running python 2 vs 3 notbob <notbob@nothome.com> - 2014-03-20 17:10 +0000
          Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 04:30 +1100
          Re: running python 2 vs 3 Gary Herron <gary.herron@islandtraining.com> - 2014-03-20 10:45 -0700
          Re: running python 2 vs 3 John Gordon <gordon@panix.com> - 2014-03-20 19:07 +0000
            Re: running python 2 vs 3 Terry Reedy <tjreedy@udel.edu> - 2014-03-20 18:05 -0400
              Re: running python 2 vs 3 alex23 <wuwei23@gmail.com> - 2014-03-21 12:37 +1000
          Re: running python 2 vs 3 Michael Torrie <torriem@gmail.com> - 2014-03-20 15:44 -0600
    Re: running python 2 vs 3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-20 18:56 +0000
    Re: running python 2 vs 3 Eric Jacoboni <eric.jacoboni@gmail.com> - 2014-03-20 20:07 +0100
      Re: running python 2 vs 3 Ned Batchelder <ned@nedbatchelder.com> - 2014-03-20 16:26 -0400
        Re: running python 2 vs 3 notbob <notbob@nothome.com> - 2014-03-20 21:16 +0000
        Re: running python 2 vs 3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-21 00:32 +0000
          Re: running python 2 vs 3 Ned Batchelder <ned@nedbatchelder.com> - 2014-03-20 21:06 -0400
            Re: running python 2 vs 3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-21 03:16 +0000
              Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 14:34 +1100
          Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 12:10 +1100
          Re: running python 2 vs 3 Ned Batchelder <ned@nedbatchelder.com> - 2014-03-20 21:20 -0400
    Re: running python 2 vs 3 Alan Meyer <ameyer2@yahoo.com> - 2014-03-20 15:53 -0400
      Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 22:08 +0200
        Re: running python 2 vs 3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-20 20:22 +0000
          Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 22:30 +0200
            Re: running python 2 vs 3 Zachary Ware <zachary.ware+pylist@gmail.com> - 2014-03-20 15:43 -0500
            Re: running python 2 vs 3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-20 20:44 +0000
              Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 22:50 +0200
                Re: running python 2 vs 3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-20 21:36 +0000
                Re: running python 2 vs 3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-21 00:59 +0000
                Re: running python 2 vs 3 Roy Smith <roy@panix.com> - 2014-03-20 21:06 -0400
                Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 13:18 +1100
                Re: running python 2 vs 3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-21 09:40 +0000
                Re: running python 2 vs 3 alister <alister.nospam.ware@ntlworld.com> - 2014-03-21 12:09 +0000
                Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 12:15 +1100
            Re: running python 2 vs 3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-20 22:39 +0000
        Re: running python 2 vs 3 Ned Batchelder <ned@nedbatchelder.com> - 2014-03-20 16:27 -0400
          Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 22:42 +0200
            Re: running python 2 vs 3 Ned Batchelder <ned@nedbatchelder.com> - 2014-03-20 16:53 -0400
              Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 22:59 +0200
                Re: running python 2 vs 3 Chris Kaynor <ckaynor@zindagigames.com> - 2014-03-20 14:18 -0700
                Re: running python 2 vs 3 Ned Batchelder <ned@nedbatchelder.com> - 2014-03-20 17:31 -0400
                Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-21 00:23 +0200
                Re: running python 2 vs 3 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-20 22:42 +0000
                Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 10:18 +1100
                Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-21 07:49 +0200
                Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 16:54 +1100
                Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-21 08:08 +0200
                Re: running python 2 vs 3 Rustom Mody <rustompmody@gmail.com> - 2014-03-20 23:51 -0700
              Re: running python 2 vs 3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-21 00:37 +0000
                Re: running python 2 vs 3 Ethan Furman <ethan@stoneleaf.us> - 2014-03-20 18:23 -0700
              Re: running python 2 vs 3 Rustom Mody <rustompmody@gmail.com> - 2014-03-20 19:20 -0700
        Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 10:04 +1100
      Re: running python 2 vs 3 Mark H Harris <harrismh777@gmail.com> - 2014-03-20 15:10 -0500
        Re: running python 2 vs 3 notbob <notbob@nothome.com> - 2014-03-20 21:28 +0000
          Re: running python 2 vs 3 Mark H Harris <harrismh777@gmail.com> - 2014-03-20 16:46 -0500
          Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-21 00:17 +0200
          Re: running python 2 vs 3 Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-21 00:29 +0000
    Re: running python 2 vs 3 Dan Stromberg <drsalists@gmail.com> - 2014-03-20 13:38 -0700
      Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 22:46 +0200
  Re: running python 2 vs 3 Mark H Harris <harrismh777@gmail.com> - 2014-03-20 11:11 -0500
    Re: running python 2 vs 3 notbob <notbob@nothome.com> - 2014-03-20 17:23 +0000
      Re: running python 2 vs 3 Chris Angelico <rosuav@gmail.com> - 2014-03-21 04:29 +1100
        Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 19:45 +0200
      Re: running python 2 vs 3 Mark H Harris <harrismh777@gmail.com> - 2014-03-20 12:42 -0500
        Re: running python 2 vs 3 Marko Rauhamaa <marko@pacujo.net> - 2014-03-20 19:47 +0200
          Re: running python 2 vs 3 Ned Batchelder <ned@nedbatchelder.com> - 2014-03-20 14:45 -0400
          Re: running python 2 vs 3 Mark H Harris <harrismh777@gmail.com> - 2014-03-20 14:36 -0500
      Re: running python 2 vs 3 Terry Reedy <tjreedy@udel.edu> - 2014-03-20 17:52 -0400
        Re: running python 2 vs 3 notbob <notbob@nothome.com> - 2014-03-20 22:19 +0000

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