Unable to set default python version to python3 in ubuntu

Question

I was trying to set default python version to python3 in Ubuntu 16.04. By default it is python2 (2.7). I followed below steps :

Answer 1

To change Python 3.6.8 as the default in Ubuntu 18.04 from Python 2.7 you can try the command line tool update-alternatives.

sudo update-alternatives --config python

If you get the error "no alternatives for python" then set up an alternative yourself with the following command:

sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 2

Change the path /usr/bin/python3 to your desired python version accordingly.

The last argument specified it priority means, if no manual alternative selection is made the alternative with the highest priority number will be set. In our case we have set a priority 2 for /usr/bin/python3.6.8 and as a result the /usr/bin/python3.6.8 was set as default python version automatically by update-alternatives command.

we can anytime switch between the above listed python alternative versions using below command and entering a selection number:

update-alternatives --config python