SHELL

install pyenv

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

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