Most of the examples I have seen in the Cython documentation have a cdef header and many also have cdefs for typing. Although optional, here is a quote from "https://www.quora.com/How-fast-is-Cython" which indicates that typing will make a big difference in Cython performance: "Just simply converting to Cython is rarely much of a win. Some tight loops with little type checking might get a boost of tens of percents, but don't bet on it. Declaring the variables as cdefs around a loop can be a big change." Even in cases where cdef is optional, there are still manual compilation steps. You're probably familiar with that already, but here is from one part of the docs: "Now following the steps for the Hello World example we first rename the file to have a .pyx extension, lets say fib.pyx, then we create the setup.py file. Using the file created for the Hello World example, all that you need to change is the name of the Cython filename, and the resulting module name . . . ". The next step is to "build the extension with the same command used for the helloworld.pyx: $ python setup.py build_ext --inplace" PysoniQ does not require these manual steps, and does not need typings or cdef headers to get optimium speed. Thanks, Mark