Now in its revised and updated 4th edition, this book teaches computational scientists how to develop tailored, flexible, and human-efficient working environments built from small programs written in the easy-to-learn, high-level Python language. As in the previous edition, the focus is on highly relevant examples and applications. These include binding together existing applications and tools, for example, for automating simulation, data analysis, and visualization. The book also covers steering simulations and computational experiments; equipping old programs with graphical user interfaces; making computational Web applications; and creating interactive interfaces with a Maple/Matlab-like syntax to numerical applications in C/C++ or Fortran. The highly regarded author, Hans Petter Langtangen, demonstrates that scripting with Python helps the programmer achieve much greater productivity, increases the reliability of scientific work and lets programmers have more fun - on Unix, Windows and Macintosh. The fourth edition corrects, updates and improves the implementation of a range of tools that have seen significant changes in recent years. The open source software tools and examples associated with the book are also improved.