Jython is an implementation of the Python programming language, seamlessly integrated with the Java platform. It allows programmers to compile Python source code to Java byte code, and run the resulting bytecode on any Java Virtual Machine. Jython offers an integration of Python and Java, so that from Python, programmers can have complete access to all Java libraries, can build applets, integrate with Java beans and subclass Java classes. Like Python, Jython can also be used interactively so that the programmer can get immediate results. Jython is complementary to Java and is especially well-suited for programming tasks like embedded scripting (Java programmers can add the Jython libraries to their system to allow end-users to write simple or complicated scripts that can add functionality to applications); interactive experimentation (Jython provides an interactive interpreter that can be used to interact with Java packages and allows programmers to experiment on the fly); and rapid application development (Python programs are typically 5-10X shorter than the equivalent Java program, which translates directly to increased programmer productivity). The seamless interaction between Python and Java allows developers to freely mix the two languages both during development and in shipping products. The library classes available to Jython are all of those available to Java (plus a good subset of the standard Python library.) "Jython Essentials" offers Java and Python programmers what they need to figure out what makes the Python and Java combination so potent for program development. They should find through the introduction to the language, examples and reference material in the book, that the secret to Jython's success lies in Java's architecture and tool set and Python's extremely rapid development.