I will discuss Reticulated Python, a system for experimenting with gradual-typed dialects of Python. It is syntactically identical to Python 3 but gives static and dynamic semantics to the type annotations already present in Python 3. Reticulated Python consists of a typechecker and a source-to-source translator from Reticulated Python to Python 3. Using Reticulated Python, we evaluated a gradual type system and three approaches to the dynamic semantics of mutable objects: the traditional semantics based on Siek and Taha (2007) and Herman et al. (2007) and two new designs. We evaluated these designs in the context of several third-party Python programs.