how to tell ubuntu to use python 3.4 instead of 2.7?

Question

I have python 2.7 and 3.4 versions installed. But when I say say "python -V", it shows version as 2.7 not 3.4

How to tell ubuntu to use newest python? where is this setting configured ?

Answer 1

if you run python -V, you get: Python 2.7.6, However, if you run python3 -V, you get 3.4.0.

Running a script, you can specify the python version to use by using either:

python <script.py>

or:

python3 <script.py>

If the script or application is executable, and you run it without the python (either 2 or 3) command, you need to have the shebang in your script, in which you define the python version to use; either:

#!/usr/bin/env python

or:

#!/usr/bin/env python3

You cannot run code, written for python2 with python3 and vice versa, so you should not (try to) "tell" Ubuntu to use either version 2 or 3 in another way then above, according to the version of python, used in your code.