SHELL

install pyenv

# Linux and Mac only (at the moment)
curl https://pyenv.run | bash

pyenv install latest version

pyenv install --list | awk '{print $1}' | grep -v - | grep -v 'a|b|c|m' | tail -1

install pip in pyenv

pyenv exec pip install numpy
or 
pyenv exec pip --version

pyenv install python version

Python 3.5:
pyenv install 3.5.4
Python 3.6:
pyenv install 3.6.8 
Python 3.7:
pyenv install 3.7.9
Python 3.8:
pyenv install 3.8.6
Python 3.9:
pyenv install 3.9.0