# Create new environment
virtualenv /path/to/project/env_name

# Create new environment and inherit already installed Python libraries
virtualenv --system-site-package /path/to/project/env_name

# Create new environment with a given Python interpreter
virtualenv /path/to/project/env_name -p /usr/bin/python/3.4

# Activate environnment
source /path/to/project/env_name/bin/activate

# Quit environment
deactivate