Debian – How to Install or Upgrade to the Latest Python Version

I'm not expert, but I believe that you shouldn't specify exact python version to use and leave that choice to system/user.

Also you should use that instead of hardcoding path to python in script:

#!/usr/bin/env python

or

#!/usr/bin/env python3 (or python2)

It is recommended by Python doc in all versions:

A good choice is usually

#!/usr/bin/env python

which searches for the Python interpreter in the whole PATH. However, some Unices may not have the env command, so you may need to hardcode /usr/bin/python as the interpreter path.

In various distributions Python may be installed in different places, so env will search for it in PATH. It should be available in all major Linux distributions and from what I see in FreeBSD.

Script should be executed with that version of Python which is in your PATH and which is chosen by your distribution*.

If your script is compatible with all version of Python except 2.4 you should just check inside of it if it is run in Python 2.4 and print some info and exit.

More to read

• Here you can find examples in what places Python might be installed in different systems.
• Here you can find some advantages and disadvantages for using env.
• Here you can find examples of PATH manipulation and different results.

Footnote

*In Gentoo there is tool called eselect. Using it you may set default versions of different applications (including Python) as default:

$ eselect python list
Available Python interpreters:
  [1]   python2.6
  [2]   python2.7 *
  [3]   python3.2
$ sudo eselect python set 1
$ eselect python list
Available Python interpreters:
  [1]   python2.6 *
  [2]   python2.7
  [3]   python3.2

You should just install the python version from the repositories. Lets assume the following:

apt-cache policy python
python:
  Installed: 2.7.6
  Candidate: 2.7.6
  Version table:
 *** 2.7.6 0
        100 /var/lib/dpkg/status
     2.7.3 0
        500 http://ftp.us.debian.org/debian/ stable/main i386 Packages

In this case, the package installed isn't available in any of the repositories. Then what we should do is downgrade the package using apt-get:

sudo apt-get install python/stable

or

sudo apt-get install python=2.7.3

or

sudo apt-get -t stable install python

This will downgrade the package seamlessly. Next time append to the package some version name like this python2.7.6 to prevent this.