They include Zope 2, the proud descendant of one of the longest-established Web server frameworks in any language; Web.py, a low-abstraction framework that provides only the essentials for Web development; Web2py, a higher-level framework that provides its own Web-based integrated development environment; Pyramid, a flexible new offering from the group that produced the popular Pylons framework; the popular and highly regarded Django framework; and CubicWeb, with which you can build not just Web applications but semantic Web applications.
Python Web frameworks: Light, heavy, and in betweenZope 2 is a descendant of Zope, the great-granddaddy of all Python Web application tools and an important branch in the Python family tree. Zope 2's ancestry, then, goes back to the mid-1990s, and Zope's continued popularity is testament to its solidity. Consequently, one huge advantage to choosing Zope 2 is that you can call on 15 years of code development and documentation.
Zope 2's "object publishing" system fits well into an object-oriented development mind-set and mitigates somewhat the learning curve you'd have to climb if you picked a framework that exposes your application to more of the more painful aspects of Web development. Zope 2 does present a formidable learning curve of its own -- but you'll at least enjoy the stability that a 15-year pedigree confers.