In this chapter, we introduced you to yet another way of optimizing or integrating C/C++ code using the C-API provided by Python and NumPy. We explained the basic structure of the code and the additional boilerplate code, which a developer has to write in order to create an extension module. Afterwards, we created two functions that calculated the square of a number and mapped the square function from the math.h library to a Numpy Array. The intention here was to familiarize you with how to leverage numerical libraries written in C/C++ to create your own modules with a minimal rewriting of code. The scope for writing C code is much wider than what is described here; however, we hope that this chapter has given you the confidence to leverage the C-API if the need arises.