The second edition of Computational Photonics, now An Introduction with Python, provides a comprehensive guide to the modelling and numerical analysis of modern photonic devices and systems. Combining the theoretical foundations of optics and electromagnetism with practical computational methods, the book enables readers to simulate and explore real photonic phenomena through hands-on numerical experiments. The text covers key topics including optical waveguides, optical fibres, semiconductor lasers, optical amplifiers, receivers, beam propagation methods (BPM), finite-difference time-domain (FDTD) simulations, solitons, solar cells, metamaterials, and includes a new chapter on plasmonics. This fully revised second edition also reflects developments in nanophotonics, integrated photonics, and modern photonic device modelling. Crucially, all computational examples have been rewritten in Python, reflecting the widespread adoption of open-source scientific computing in research and education. With numerous simulation programs, exercises, and projects, the book provides students and researchers with practical tools for studying and designing photonic devices.