How do I pick the right python in Linux env?

[MDRI]

How do I pick the right python in Linux env?
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Thanks for reviewing my threads. I have a pyhton code developed in Windows Eclipse PyDev IDE. As I place this code in Linux environment, I am finding some challenges.

I added

#!/usr/bin/env python

to code in linux box xmlcode.py.

I find many python version like Python 2.3, 2.6, 3.2 etc

I made this code file to have execute privilege.

./xmlcode.py ==> throw file not found.

python xmlcode.py ==> not producing output

I find /usr/lib64/python2.6/site-packages/lxml in linux server

but import xml.etree.ElementTree as ET
from lxml import etree

not picking up in my code run

How do I pick the correct python version env for my code?

How do I bring xml.etree.ElementTree , lxml to above correct python version env?

What are the linux env (variable) set up required for my code to work?

Thanks for your guidance.