upgrade to python 3.7 ubuntu 18.04 code example

Example 1: linux ubuntu install python 3.7

sudo apt-get install python3.7

Example 2: how to upgrade python from 2.7 to 2.9 on ubuntu 14.04

git clone https://github.com/pyenv/pyenv.git ~/.pyenv
 git clone https://github.com/pyenv/pyenv-virtualenv.git ~/.pyenv/plugins/pyenv-virtualenv