Python: virtualenv Tutorial
virtualenv is a tool to create isolated Python environments, so you can install different version of python and different versions of library.
◆ virtualenv You must provide a DEST_DIR Usage: virtualenv [OPTIONS] DEST_DIR Options: --version show program's version number and exit -h, --help show this help message and exit -v, --verbose Increase verbosity. -q, --quiet Decrease verbosity. -p PYTHON_EXE, --python=PYTHON_EXE The Python interpreter to use, e.g., --python=python2.5 will use the python2.5 interpreter to create the new environment. The default is the interpreter that virtualenv was installed with (/usr/bin/python) --clear Clear out the non-root install and start from scratch. --no-site-packages DEPRECATED. Retained only for backward compatibility. Not having access to global site-packages is now the default behavior. --system-site-packages Give the virtual environment access to the global site-packages. --always-copy Always copy files rather than symlinking. --unzip-setuptools Unzip Setuptools when installing it. --relocatable Make an EXISTING virtualenv environment relocatable. This fixes up scripts and makes all .pth files relative. --no-setuptools Do not install setuptools (or pip) in the new virtualenv. --no-pip Do not install pip in the new virtualenv. --extra-search-dir=DIR Directory to look for setuptools/pip distributions in. This option can be used multiple times. --never-download DEPRECATED. Retained only for backward compatibility. This option has no effect. Virtualenv never downloads pip or setuptools. --prompt=PROMPT Provides an alternative prompt prefix for this environment. --setuptools DEPRECATED. Retained only for backward compatibility. This option has no effect. --distribute DEPRECATED. Retained only for backward compatibility. This option has no effect.
see also Python: What's PyPi, pip, easy_install, setuptools?