free and open-source web framework written in Python
See Wikipedia for details. Quote:
Django's primary goal is to ease the creation of complex, database-driven websites. Django emphasizes reusability and "pluggability" of components, rapid development, and the principle of don't repeat yourself. Python is used throughout, even for settings, files, and data models. Django also provides an optional administrative create, read, update and delete interface that is generated dynamically through introspection and configured via admin models.
Some well-known sites that use Django include Pinterest, Instagram, Mozilla, The Washington Times, Disqus, the Public Broadcasting Service, and Bitbucket.