Steps:
- Install python3 (follow https://docs.python-guide.org/starting/install3/osx/)
- Install virtualenv
pip3 install virtualenv
- Make a virtual environment within current directory
virtualenv -p python3 ./venv
- Activate the virtual environment for working with it
source ./venv/bin/activate
- Deactivate it when done (Why? So you can work with other virtual environments or the global environment)
deactivate