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JES: Jython Environment for Students

JES is a development environment designed for Media Computation. It allows students to use the Python programming language (specifically, Jython, which is a version of Python implemented in Java) to manipulate images, sounds, and videos.

JES is incorporated in "Introduction to Computing and Programming in Python: A Multimedia Approach," by Mark Guzdial and Barbara Ericson. Dr. Guzdial is the project leader, and the project has been worked on by many people over the years (as seen in the jes/help/JESCopyright.txt file).

JES is Free Software, made available under the GNU General Public License. This means that everyone may use JES, free of charge, and share it with anyone. Everyone can also make changes to JES and share those changes. You can read the full license information in the jes/help/JESCopyright.txt file.

Running JES

The easiest way to run JES is with a downloadable package, which you can find at Each of them includes its own JESReadme.txt with instructions.

If you're working on JES, or you just want to run the latest development version:

  1. Download a Java Development Kit and Apache Ant.
  2. Use Git to clone the JES repository, or download a .zip file of the repository.
  3. Build JES by running ant.
  4. Run the shell script if you're on Mac or Linux, or the jes.bat batch file if you're on Windows.

What's in the repository

The build.xml is used by developers to launch JES and run all of its tests. It contains instructions for Apache Ant ( You can run ant build to build JES, ant test to run all the tests, and ant clean to erase everything you built.

The file launches JES on Mac and Linux, and JES.bat does the same on Windows.

All the source files and resources for JES itself live in the jes folder:

  • jes/java: The Java code that contains the core of JES, including the code that directly handles pictures, sounds, and movies.

  • jes/python: The Python code that controls most of the user interface.

  • jes/images: The pictures that are used by JES itself, such as the splash screen and the toolbar buttons.

  • jes/help: Web pages (and a few text files) about how to use JES.

  • jes/classes: When the Java code is compiled, the class files are placed here.

  • jes/javadoc: API documentation for the Java parts of JES. (This isn't actually accessible from inside JES anymore, but the code for browsing it is still present.)

In addition, JES uses some code written by others, which we store alongside JES in the dependencies folder:

  • dependencies/jars: JAR files for a bunch of libraries the JES Java code uses to work with media files.

  • dependencies/jython: An installation of Jython, currently version 2.5.3. We need to keep this around because the Jython JAR doesn't have the standard library.

  • dependencies/python: Python libraries used by JES.

  • dependencies/jmusic-instruments: Instrument classes to use with the bundled copy of jMusic. This contains the Java source files and class files, but JES actually imports them from a JAR file in dependencies/jars.

The tests folder contains Python programs that test different parts of JES to make sure we wrote them according to the specifications. You can run these from inside JES by opening the file, but it's much easier to just use ant test.

The releases folder is where JES releases (like ZIP files, Windows installers, or Mac applications) are built. You can build them by running ant release, and they appear directly inside the releases folder.

  • The releases/build-releases.xml file contains the Ant instructions for building each kind of release. (Ant considers it part of build.xml, so you can't run it by itself.)

  • The releases/resources folder contains files that get included as part of the releases, like README files or platform-specific installers.

  • The releases/stage folder is used by Ant to arrange all the files for the releases before it actually zips them all up.

If you just run ant release, it generates a "snapshot release" suitable for testing. If you want to build proper releases, build Windows installers, or sign the released JAR files, there are instructions in working-on-jes/

The demos folder contains programs you can run to try out JES.

The working-on-jes folder contains articles written by the JES developers about how JES works, and how you can even contribute to it!


The Jython Environment for Students allows students to write Jython programs that can manipulate pictures, sounds, and videos.



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