Long in development, the new major release of the Python-to-C compiler sheds legacy Python support and readies Cython developers for big changes in Python.

Cython* is a superset of Python* that additionally supports C functions and C types on variable and class attributes. Cython is used for wrapping external C libraries that speed up the execution ...

Those improvements will show up even in Cython code built from Python 3.5 modules, but if you’re running Python 3.6, the faster call methods will be used in regular (non-Cython) code as well.