1. virtualenv
pip install virtualenv
virtualenv testvir (the name of the virtual environment set by yourself)
activate.bat to enter the virtual environment
deactivate.bat exit the virtual environment
2. virtualenvwrpper
pip install virtualenvwrpper
mkvirtualenv testvir (set the name of your own virtual environment)
workon testvir (start one of your virtual environments)
pip list (look at the packages installed in your virtual environment)
pip install
pip uninstall
deactivate (close the currently running virtual environment)