Two versions of python on linux. how to make 2.7 the default

Question

I've got two versions of python on my linuxbox:

$python
Python 2.6.6 (r266:84292, Jul 10 2013, 22:48:45) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 


$ /usr/local/bin/python2.7
Python 2.7.3 (default, Oct  8 2013, 15:53:09) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 

$ which python
/usr/bin/python
$ ls -al /usr/bin/python
-rwxr-xr-x. 2 root root 4864 Jul 10 22:49 /usr/bin/python

How can I make 2.7 be the default version so when I type python it puts me in 2.7?

When I did this to my fedora the yum or apt-get did not work any more. — User
@User: Yeah, I broke an ancient Mandrake similarly (changing /usr/bin/env python to mean 2.6 instead of 2.3 meant half of the commands in rpm and all of urpmi stopped working). — abarnert
I have followed the following step to install Django on Centos 5:1st, install Python 3.6 from source code. 2nd: in shell type the following command "alias python=/usr/local/bin/python3.6" 3rd: run following command to install Django "pip3 install Django" 4th: "python -m django --version" to verify the Django installed with version "1.10.5" — showmyroutes
for me /usr/bin/python was a soft link pointing to python2 . I just changed it to python3.6 — munish

abarnert abarnert · Accepted Answer · 2013-10-08T19:17:34

You probably don't actually want to change your default Python.

Your distro installed a standard system Python in /usr/bin, and may have scripts that depend on this being present, and selected by #! /usr/bin/env python. You can usually get away with running Python 2.6 scripts in 2.7, but do you want to risk it?

On top of that, monkeying with /usr/bin can break your package manager's ability to manage packages. And changing the order of directories in your PATH will affect a lot of other things besides Python. (In fact, it's more common to have /usr/local/bin ahead of /usr/bin, and it may be what you actually want—but if you have it the other way around, presumably there's a good reason for that.)

But you don't need to change your default Python to get the system to run 2.7 when you type python.

First, you can set up a shell alias:

alias python=/usr/local/bin/python2.7

Type that at a prompt, or put it in your ~/.bashrc if you want the change to be persistent, and now when you type python it runs your chosen 2.7, but when some program on your system tries to run a script with /usr/bin/env python it runs the standard 2.6.

Alternatively, just create a virtual environment out of your 2.7 (or separate venvs for different projects), and do your work inside the venv.

Two versions of python on linux. how to make 2.7 the default

7 Answers