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running python 2 vs 3

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  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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#68585

On 3/20/14 9:58 AM, notbob wrote:

> I've installed python 3.3 on my Slack box, which by default comes with
> python 2.7.  I know how to fire up the different IDLE environments,
> but how do I differentiate between the scripts?

hi notbob, the two (or more) IDLE environments run very nicely 
side-by-side. If you access your scripts from the same directory (I do 
not) there really is no problem. The reason is that the .pyc files 
created for python2.x are only used by python2.  The .pyc files for 
python3.x are kept (by a naming convention) in __pycache__ , so there 
really is no problem.  Having said that, the only problem is that your 
script for python3 might not run in python2 (for various reasons) but 
the problem is not that the scripts are contained in the same folder.

I keep my python2 scripts in one folder ~/Documents/Python2/ and my 
python3 scripts in another one ~/Documents/Python3/

I add the two folders in the python paths browser (using site-packages) 
so that when I start IDLE for python2 it pulls its scripts from 
~/Documents/Python2/  and when I start IDLE for python3 it pulls its 
scripts from  ~/Documents/Python3/

There are *many* ways to organize this. Often I have to maintain two 
scripts (packages) one for each version. Although, I try to make my 
scripts run in both environments.  Often I have IDLE(2) ane IDLE(3) 
running and testing at the same time on the same box. This works very well.

marcus

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#68588

On 2014-03-20, Mark H Harris <harrismh777@gmail.com> wrote:

> not) there really is no problem. The reason is that the .pyc files 
> created for python2.x are only used by python2.  

Lordy, what hath I wrought!?  ;)

What the heck is a .pyc file and how are they created?  Actually, I
can see  it's a compiled binary, but I where did it come from?  

I went back to my ~/python/ dir and noticed one .pyc file out of 15
.py files I created from following Learning Python the Hard Way.  No
one said anything about creating a binary.  I know I discovered how to
create/edit python scripts from IDLE.  Is that it?  I've been using
gedit and emacs up till now.  Seems the file with the .pyc file is the
one I edited in IDLE.  Is that why LPtHW eschews IDLE for gedit?  

Why do I feel like I've really stepped in it?  ;)

nb

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#68589

On Fri, Mar 21, 2014 at 4:23 AM, notbob <notbob@nothome.com> wrote:
> On 2014-03-20, Mark H Harris <harrismh777@gmail.com> wrote:
>
>> not) there really is no problem. The reason is that the .pyc files
>> created for python2.x are only used by python2.
>
> Lordy, what hath I wrought!?  ;)
>
> What the heck is a .pyc file and how are they created?  Actually, I
> can see  it's a compiled binary, but I where did it come from?
>
> I went back to my ~/python/ dir and noticed one .pyc file out of 15
> .py files I created from following Learning Python the Hard Way.  No
> one said anything about creating a binary.  I know I discovered how to
> create/edit python scripts from IDLE.  Is that it?  I've been using
> gedit and emacs up till now.  Seems the file with the .pyc file is the
> one I edited in IDLE.  Is that why LPtHW eschews IDLE for gedit?
>
> Why do I feel like I've really stepped in it?  ;)
>

You should be able to completely ignore .pyc files, most of the time.
The only thing to remember is that you should delete them any time you
delete the corresponding .py files. They're a cached version that
Python will use to speed up imports, nothing more.

Nowadays they'll be pushed away into a separate directory, which makes
them easier for you to ignore. This is a good thing.

ChrisA

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#68592

Chris Angelico <rosuav@gmail.com>:

> Nowadays they'll be pushed away into a separate directory, which makes
> them easier for you to ignore. This is a good thing.

Still, I don't think Python should go and soil my directories without an
explicit permission.


Marko

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#68591

On 3/20/14 12:23 PM, notbob wrote:

> What the heck is a .pyc file and how are they created?  Actually, I
> can see  it's a compiled binary, but I where did it come from?

The world according to me:  python is an interpreter (vs compiler) which 
converts your source code into tokens and then into a bytecode.

The process takes time. So, the solution is to place the tokenized stuff 
into a .pyc file so that the process does not have to be repeated 
unless, of course, the source has changed since the last .pyc file create.

It used to be that the .pyc files went into the same dir as the source 
(that's how it works for python2) but now with python3 they go into a 
directory in your source tree called __pycache__,  and they are named 
based on python version  (a way better scheme for sure).

If you wanted to you could run your python scripts from the .pyc file 
alone. In other words, you may import as long as the .pyc file exists 
and the source does not need to be there.  Some folks use this (not 
recommended) trick to hide or obfuscate their source from their users).

marcus

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#68593

Mark H Harris <harrismh777@gmail.com>:

> If you wanted to you could run your python scripts from the .pyc file
> alone. In other words, you may import as long as the .pyc file exists
> and the source does not need to be there. Some folks use this (not
> recommended) trick to hide or obfuscate their source from their
> users).

I've seen it done, but at least in those Python 2 days the pyc format
changed between minor releases of Python, so Python itself had to be
shipped with the pyc files.


Marko

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#68597

On 3/20/14 1:47 PM, Marko Rauhamaa wrote:
> Mark H Harris <harrismh777@gmail.com>:
>
>> If you wanted to you could run your python scripts from the .pyc file
>> alone. In other words, you may import as long as the .pyc file exists
>> and the source does not need to be there. Some folks use this (not
>> recommended) trick to hide or obfuscate their source from their
>> users).
>
> I've seen it done, but at least in those Python 2 days the pyc format
> changed between minor releases of Python, so Python itself had to be
> shipped with the pyc files.
>

Python3 still makes no guarantees about the compatibility of bytecode 
(and therefore .pyc files) across versions of Python, so if you want to 
run from pure .pyc files, you have to be sure to use the same version of 
Python that produced the files.

--Ned.

>
> Marko
>


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

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#68601

On 3/20/14 12:47 PM, Marko Rauhamaa wrote:
> I've seen it done, but at least in those Python 2 days the pyc format
> changed between minor releases of Python, so Python itself had to be
> shipped with the pyc files.

hi Marko, yeah, I have not done this; being that the concept is contrary 
to my principles and sensibilities these days. So,

   1) no intellectual property
   2) no software idea patents
   3) no obfuscated code
   4) ship the source, or don't ship anything/

In my view coding (and all other aspects of computer science including 
software engineering) is a liberal art; it should be open, free (libre), 
and available to everyone. People learn best by doing, and the do best 
by reading what others have done before them.

marcus

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#68629

On 3/20/2014 1:23 PM, notbob wrote:

> What the heck is a .pyc file and how are they created?

.pyc contained compiled bytecode. They are created when, and only when, 
you import a module.  Imported library files are often big and stable, 
so their compiled forms get cached. Top-level scripts are typically 
short and often volotile. They may be as short as "from start import 
run; run()" in order to have as much as possible stored in compiled form.

This has nothing to do with Idle.

> I went back to my ~/python/ dir and noticed one .pyc file out of 15
> .py files I created from following Learning Python the Hard Way.

That must be the only one you imported.

-- 
Terry Jan Reedy

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#68633

On 2014-03-20, Terry Reedy <tjreedy@udel.edu> wrote:

> That must be the only one you imported.

So it is.  Thank you.

nb

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