update python 3 ubuntu code example

Example 1: update ubuntu to python 3.85

sudo apt-get install python3.8

Example 2: update python ubuntu

sudo apt-get update && sudo apt-get upgrade
sudo apt-get install python3.7

Example 3: how to upgrade 3.6 to 3.7 on linux

sudo apt-get install python3.7

Example 4: update python ubuntu

$ sudo apt update -y
$ sudo apt install python3.7