Run a UNIX script to use different versions of python

Question

I have a UNIX script which is used to initialize the environment and properties of the project. It uses python. I had to refer the path. This will be used as a common file and used across multiple developers. Few of the machines uses Python 1.x and 2.x. Few others uses only Python 3.x.

So /usr/bin/python works for the machines run Python 1.x but it fails in machines running python 3.x. I have to explicitly change it to /usr/bin/python3 to make it work.

How can I handle the situation to make the script run independent of the python version installed.

Usually when Python 3 is installed, the command python should be available and be an alias for python3. If the script supports both Python 2 and 3, then it shouldn't matter whether python refers to Python 2 or 3. In other words, it should work simply with /usr/bin/python either way, no? — deceze
– deceze ♦, Commented May 13, 2022 at 14:56
I started in this line of work in 2008, and i've never seen python 1.x in the wild. — jordanm
– jordanm, Commented May 13, 2022 at 14:56

martineau · Accepted Answer · 2022-05-13 15:54:07Z

1

Python 1 or 2 are dead obviously, but I'll try to answer your question

In this this case you should have seprate binaries for each python version, similar to:

/usr/bin/python1
/usr/bin/python2
/usr/bin/python3

In your script define the version you want to use using shebang

For example make a file my_old_script.py:

#!/usr/bin/python2

import sys

print(sys.version)

Give the script execution permission:

chmod +x my_old_script.py

Then execute it without specifying an interpreter:

./my_old_script.py

output:

2.7.17 (default)
[GCC 7.5.0]

edited May 13, 2022 at 15:54

martineau

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answered May 13, 2022 at 15:11

ahmed

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2 Comments

ljmc Over a year ago

That makes the script entirely dependent on which python version is installed, the question is how to make it independent.

ahmed Over a year ago

That's simply not possible without some weird hacking, this is one why to handle tasks with different scripts and python versions. This how current must distro handle python2 and 3 distribution, in Ubuntu you will find python3, python3.x and python2 each point to a different version of python

ljmc · Accepted Answer · 2022-05-13 15:08:10Z

0

Python2 is dead (less so that python1, but still dead), so it should be less and less of an issue. If you are worried about python2/3 compatibility, there is six and most things have been backported through the __future__ module, hopefully those two should be enough for your use cases.

answered May 13, 2022 at 15:08

ljmc

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