update python on linux code example

Example 1: ubuntu install python

# first do:
sudo apt-get update
# after do:
sudo apt-get install python3.6
# then it should be installed

Example 2: how to install python3 in ubuntu

sudo apt update
sudo apt install software-properties-common
sudo add-apt-repository ppa:deadsnakes/ppa
sudo apt update
sudo apt install python3.8