Python virtualenv

python-virtualenv

# creating the env
$ virtualenv --no-site-packages -p /path/to/python3 virtualenv_name
## --no-site-packages seems to be depricated as said here:
## https://virtualenv.pypa.io/en/stable/reference/#cmdoption-no-site-packages

## mind PYTHONPATH and pip -E, and to freez system pip:
## https://stackoverflow.com/questions/1382925/virtualenv-no-site-packages-and-pip-still-finding-global-packages

# activate/de
$ source virtualenv_name/bin/activate
(virtualenv_name)$ deactivate