This Book is the result of a varied experience acquired by the author in the field of fluid mechanics. The goal that we set ourselves for the writing of the book is to provide the reader with all the tools necessary for understanding the topics of computational fluid dynamics starting with brief references to fluid mechanics, showing the difficulties in solving the governing equations, to arrive at the different numerical approaches adopted in the scientific literature, focusing on the finite difference method. To make the exposition of the topics clearer, we wanted to explain some engineering applications developed in the Python environment.