How to edit default python version for a linux user?

Edit the bash profile and add an alias using the following code

$ nano ~/.bashrc

Put the following line of code in .bashrc file and alter the python3.6 path as per your new installation

alias python='/usr/local/bin/python3.6'

Use CTRL x to exit and save
After that you need to reload the source, so use the following command and you are good to go.

$ source ~/.bashrc