Yet Another Python Python(YAPyPy), which is extended from and compatible to the original CPython.
With YAPyPy in Python3.6+, you can run any Python 3.x source codes with full compatibilities.
Pattern matching and other popular syntax sugars would be added.
Anything could be implemented in a trivial way through multiphase Python( interpreters are provided for you to change ASTs or even calculate constant values/procedure structures before bytecode emitted).
You can write your own passes to optimize Python bytecode in specific scenes, or even perform JIT techniques when it's possible.