Dealing with python version

[Harry George]

Andrei Kulakov <ak at silmarill.org> writes:

> Hello,
> 
> Correct me if I'm wrong, but it seems like if python1.6 or 2.0 are
> already installed and you install a newer version, python command still
> points to the old interpreter.
> 
> I think it would be sensible to use the newest installed python to run
> a program. Is there some elegant way to do that?
> 
> I would ideally prefer it to run using newest interpreter available
> unless it's older than some minimum requirement. It's not very
> user-friendly to put #!/usr/bin/env python2.1 bang line and then say in
> a README that if user gets an error, he has to somehow find out what's
> the latest version he's got and change the bang line to it.
> 
> What's the proper way to deal with all of this?
> 

I'll assume *NIX, and more specifically Linux (because it has python
scripts scattered through the std installation).  Typically, the
preinstalled scripts are expecting a specific version of python, and
expect to find it via: 

    #!/usr/bin/python 
or 
    #!/usr/bin/env python

You don't want to screw up those preinstalled scripts, so don't do
anything to the original installation.  Instead, install new version
elsewhere, e.g.:

  /usr/local/bin/
        python2.0 
        python2.1
  /usr/local/lib/
        python2.0
        python2.1

Each installation will create a generic "python" binary (e.g.,
/usr/local/bin/python) as well as the versioned name.  Delete the
generic one, so it doesn't interfere with the preinstalled python.
That leaves the problem of accessing the new ones.  I use little
scripts:

  /usr/local/bin
        py20
        py21

Where py20 is, e.g.:
  #!/bin/sh
  unset PYTHONHOME PYTHONPATH PYTHONLIB
  /usr/local/bin/python2.0 "$@"

To use:
  py20 myprogram.py

Can also start scripts with:
  #!/usr/local/bin/python2.0


> Thanks,
> 
>  - Andrei
> 
> -- 
> Cymbaline: intelligent learning mp3 player - python, linux, console.
> get it at: cy.silmarill.org

-- 
Harry George
hgg9140 at seanet.com