setting default python version ubuntu code example
Example 1: set python 3 as default ubuntu
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.4 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.6 2
Example 2: set python 3 as default ubuntu
sudo update-alternatives --config python
Example 3: set python 3 as default ubuntu
update-alternatives: error: no alternatives for python3