This book covers the fundamental concepts in signal processing illustrated by using Python code. All the code used is available for download as an interactive IPython notebook. The computations examined can be modified using the IPython notebook to explore the corresponding concepts. The author provides examples that allow the reader to experiment and learn as they read. The book focuses on principles and signal processing which are fundamental and do not go out of date. The code corresponding to this book uses core functionality of the scientific Python stack that should remain unchanged into the foreseeable future.