In command line of directory desired:
virtualenv venv
virtualenv venv --python=python3
source venv/bin/activate
deactivate
pg_ctl -D /usr/local/var/postgres start
In command line of directory desired:
virtualenv venv
virtualenv venv --python=python3
source venv/bin/activate
deactivate
pg_ctl -D /usr/local/var/postgres start