running Python2 Python3 parallel concurrent


H

harrismh777

Greetings,

The purpose of this communique is to document a process for
installing python2.7.1 in parallel with python3.2 on a concurrent
desktop with independent idle and python path structure.

Each version (python2, python3) will be installed in a separate
python shell (idle) run on a separate local install so that both
versions are running side-by-side on the same user desktop, each python
shell having a unique .idlerc(v) configuration dir for look&feel as well
as separate recent files lists and separate working .py folders.

Neither of the installs should affect the other installation (nor
idle operation), nor should the installs affect the system-wide default
install (python2.6.2 in my case running ubuntu 9.04 jaunty). As well,
the search paths should not overlap except at the top $HOME level. The
over-all purpose is to be able to play with both versions together in
order to facilitate/enable/solve concurrent development, migration, and
debug issues between the two versions.

I trust that if the community has already solved this problem, and
has a better way, that I may discover it and be able to adopt it to my
own environment as well.

If you find any mistakes, please let me know.

Best regards, m harris.

The primary unordered issues for solution(s) are:

1) separate PythonX folders for .py files, $HOME/PythonX
2) separate desktop launchers to cleanly launch idleX for pythonX
3) separate .idlercX files in the home dir for IDLE pythonX
4) separate correct $HOME/local/pythonX installation folders
5) separate correct $HOME/bin/ launch scripts and sym links
6) Config from sources with correct --prefix setting
7) Local Build & Install

===========================================================
BUILD VERSIONS FROM SOURCE
===========================================================
Download the 2.7.1 and 3.2 tarballs from here:

http://www.python.org/download/

From your $HOME directory create the modules (.py) folder with:

mkdir Python3 ie., $HOME/Python3/

.... and then create the local installation folder in $HOME/local:

mkdir local
cd local
mkdir python3 ie., $HOME/local/python3/

Create a $HOME/bin/ folder, if it does not already exist.

Unpack each tarball in $HOME with:

tar -xvf Python-3.2.tar.bz2 --bzip2

cd Python-3.2 and then build & install with:

./configure --prefix=$HOME/local/python3
make
make install

NOTES: Repeat these steps for each local version. It is important
that the development headers already be installed, including the tk-dev
package so that tkinter mod will get built enabling idle. The tarballs
are available in several compression schemes... I chose bzip2.
The --prefix option tells the installer where pythonX will live;
this will be a local install visible only to the development user.

===========================================================
Symbolic link(s)
===========================================================

Create a symbolic link for python in $HOME/bin/ with:

cd $HOME/bin/
ln -sf $HOME/local/python3/bin/python3 python3

note: (python3 can now be invoked from a linux terminal)

Repeat the steps for each version.

You may need to set your linux path to include
$HOME/bin/ in either .profile or .bashrc if not
already in place. This is usually already set on
most modern linux distros if ~/bin/ exists.

===========================================================
Launcher Scripts
===========================================================

Create the bash launcher script used for setting the
PYTHONPATH and starting the python3 script. Use a text
editor of your choice to create a text file in $HOME/bin/
called Python3-IDE containing these three lines:

#!/bin/sh
export PYTHONPATH=$HOME/Python3
exec $HOME/bin/idle-python3 -n

Now, create the python script for importing and launching
the PyShell from idlelib; use a text editor to create a
text file in $HOME/bin/ called idle-python3 containing:

#!/home/<username>/bin/python3

from idlelib.PyShell import main
if __name__ == '__main__':
main()

The first line /home/<username>/ is $HOME, but may have to
be spelled out in the script above. Now, set both scripts
executeable with:

chmod 0754 $HOME/bin/Python3-IDE
chmod 0754 $HOME/bin/idle-python3

Notes: Repeat for each version. Summary; each version will
have its own launcher script ( PythonX-IDE ) and each will
have its own python idle starter script ( idle-pythonX ).

The launcher script is the 'called' file from the Desktop
launcher icon, which sets the PYTHONPATH. The python idle
starter script correctly starts the interpreter and then
initiates the PyShell (python idle shell) import main and
run.

===========================================================
IDLE Configuration File .idlrcX
===========================================================

By default the idlelib.configHandler sets the config
dir to $HOME/.idlerc (we will change this so that
each idle version will have its own config directory
in $HOME). The cfgDir attribute is held in the config
handler in the following module hierarchy:

[module] idlelib.configHandler

Class IdleConf

def GetUserCfgDir()

cfgDir='.idlerc'

Use a text editor and "carefully" change the config
handler located here:

$HOME/local/python3/lib/python3.2/idlelib/configHandler.py

(you might want to backup the configHandler.py file just in
case you honk it somehow... ) :)

Find the Class IdleConf and then locate the def called:
GetUserCfgDir()

Change the attribute cfgDir to:
cfgDir='.idlerc3'

Save the file.

Notes: Repeat for each version. Summary, each version will
have its own .idlercX configuration file:

.idlerc3
.idlerc2

Also, the default python installation will still have its own
configuration file .idlerc specific to the system-wide IDLE
config.

===========================================================
Construct Desktop Launchers
===========================================================

Build each Desktop python application launcher in the
usual way, and point the lancher to $HOME/bin/Python3-IDE

Repeat this step for each version application launcher.

===========================================================
DONE enjoy a cup of tea
===========================================================

At this point you should be able to launch each python version in
its own python shell from the Desktop and have them both running
concurrently side-by-side without stepping on one anothers toes, as it
were, and each having its own environment look & feel.

I actually set one of the shells to have differing colors and font
so that I can visually remember which environment I'm coding to. Also, I
keep my python3.py files only in Python3 and my python2.py files only in
Python2. In this way they can have the same names exactly but because
the path structures are completely isolated the correct .py is imported
depending on the version environment.

Kind regards,

m harris
 
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J

John Roth

Greetings,

     The purpose of this communique is to document a process for
installing python2.7.1 in parallel with python3.2 on a concurrent
desktop with independent idle and python path structure.

...

     Kind regards,

     m harris

 python2-python3-parallel.txt
7KViewDownload

You might want to look at PEP 394, which is tentatively scheduled for
Python 3.3 and the next maintenance release of 2.7. As far as I can
tell, this pretty much solves the problem for Unixoid and MacOS
systems. PEP 397 is a first cut at doing the same thing for Windows.

Regards,
John Roth
 
H

harrismh777

John said:
You might want to look at PEP 394, which is tentatively scheduled for
Python 3.3 and the next maintenance release of 2.7. As far as I can
tell, this pretty much solves the problem for Unixoid and MacOS
systems.

Thanks John. I finally read PEP 394 and 397. Yes, these handle the
problem on the execute end. The solution to the problem on the
application development end (my stuff, see previous) is concerning the
requirement to be able to build apps for both versions in parallel---
from the development end.
Ultimately, it would be nice to have support in IDLE for multiple
versions from under the umbrella of one IDE. I have decided that rather
than try to port 32 -> 2.7 ( or 27. -> 3.2 ) that I will be developing
for both (in parallel) concurrently. When I am done with the app two
versions will be able, one sh-banged for 2.7 and the other sh-banged for
3.2/
At the moment I am using two instances of IDLE running in parallel, one
using 2.7.1 and the other using 3.2 / I would like to see them
combined under one IDE with configuration options for multiple version
environments (perhaps in addition to 2.7 , 3.2).
So, I'm playing a bit with IDLE to see what I can come up with. I don't
know if anyone wants to see a PEP on that or not.
And, while I'm at it, I think I'll look into a way to provide a clear
screen option for the IDLE interactive window... :)

kind regards,
m harris
 
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R

rusi

Greetings,

     The purpose of this communique is to document a process for
installing python2.7.1 in parallel with python3.2 on a concurrent
desktop with independent idle and python path structure.

Not sure if this is relevant...
python-mode (emacs mode for python development) is broken for python 3
I submitted a 1-line patch which makes python-mode work for 2.x and
3.x
Here https://bugs.launchpad.net/python-mode/+bug/450552
 

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