Python egg
A way to package and distribute Python packages. Each egg contains a setup.py file with metadata (such as the author's name and email address and licensing information), as well as information about dependencies. setuptools, the Python library that powers the egg mechanism, is able to automatically find and download dependencies for eggs that you install. It is even possible for two different eggs to concurrently use different versions of the same dependency. Eggs also support a feature called entry points, a kind of generic plug-in mechanism. Much more detail is available at the PEAK website.