I read this without finding the solution: http://docs.python.org/install/index.html
The "normal" way is to:
cd to the resulting directorypython setup.py installAnother solution is to use easy_install. Go to http://peak.telecommunity.com/DevCenter/EasyInstall), install the package using the instructions on that page, and then type, in a Terminal window:
easy_install BeautifulSoup4
# for older v3:
# easy_install BeautifulSoup
easy_install will take care of downloading, unpacking, building, and installing the package. The advantage to using easy_install is that it knows how to search for many different Python packages, because it queries the PyPI registry. Thus, once you have easy_install on your machine, you install many, many different third-party packages simply by one command at a shell.