Web2py was created by Massimo Di Pierro, a professor of computer science at DePaul University, as his attempt to build a Python-based Web framework that was easy to use as well as powerful. It's a well-crafted, rock-solid framework that, like Zope 2, provides its own development environment.
An example of Web2py's convenience is its uncluttered API. The Web2py core is trimmed to an essential 12 objects, largely thanks to the fact that the API was completely designed before being implemented. In addition, Web2py boasts a small footprint: about 300KB of code for the system core, database abstraction layer, templating language, and supporting functions.
Examples of Web2py's power are its Web-based soup-to-nuts administration and development console, the database abstraction layer that supports virtually every RDBMS that Python can support, and its "components" -- Web-page entities that are provided with their own view/controller code, but are manipulated via AJAX so that component updates don't require full-page updates.
Web2py lives happily with any 2.x version of Python, though the official supported version is 2.5. It will also run on Jython. It provides its own built-in Web server -- specifically, the CherryPy Web server -- though any WSGI-compliant Web server will suffice.