Now that we've got our first example out of the way, we're going to take a little bit of a detour and learn how to obtain and install third-party modules. This is important, as we'll install a few throughout the remainder of the book.
The Python community maintains a centralized package repository, termed the Python Package Index (or PyPI). It is available on the web at http://pypi.python.org. From there, it is possible to download packages as compressed source distributions, or in some cases, pre-packaged Python components. PyPI is also a rich source of information. It's a great place to learn about available third-party applications. Links are provided to individual package documentation if it's not included directly into the package's PyPI page.
There are at least two different popular methods of packaging and deploying Python packages. The distutils package is part of the standard distribution and provides a mechanism for building and installing Python software. Packages that take advantage of the distutils system are downloaded as a source distribution and built and installed by a local user. They are installed by simply creating an additional directory structure within the system Python directory that matches the package name.
In an effort to make packages more accessible and self-contained, the concept of the Python Egg was introduced. An egg file is simply a ZIP archive of a package. When an egg is installed, the ZIP file itself is placed on the Python path, rather than a subdirectory.