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Jython: Python for the Java Platform

Maven Central Javadocs

This is the development repository of Jython, the implementation of Python 2.7 in Java. Along with good (not perfect!) language and runtime compatibility with CPython 2.7, Jython 2.7 provides substantial support of the Python ecosystem. This includes built-in support of pip/setuptools (you can use bin/pip if the targets do not include C extensions) and a native launcher for Windows (bin/jython.exe) that works essentially as the python command.

Jim Baker presented a talk at PyCon 2015 about Jython 2.7, including demos of new features:

See ACKNOWLEDGMENTS for details about Jython's copyright, license, contributors, and mailing lists. Consult NEWS for detailed release notes, including bugs fixed, backwards breaking changes, and new features. We sincerely thank all who contribute to Jython, by bug reports, patches, pull requests, documentation changes and e-mail discussions.

How to build Jython

The project uses Mercurial for version-control, and the master repository is at, while the repository on GitHub is just a mirror of that. You may clone either repository to create a buildable copy of the latest state of the Jython source.

Build using ant for development

Jython is normally built using ant. It is necessary to have Ant and at least a Java 7 SDK on the path. To build Jython development use, we generally use the command:


This leaves an executable in dist/bin that you may run from the check-out root with:


Other ant targets exist, notably clean, and jar.

You can test your build of Jython (by running the regression tests), with the command:

dist/bin/jython -m test.regrtest -e -m regrtest_memo.txt

Build an installer using ant

If you want to install a snapshot build of Jython, use the command:

ant installer

This will leave you with a snapshot installer JAR in dist, that you can run with:

java -jar jython-installer.jar

for the graphical installer, or:

java -jar jython-installer.jar --console

For the console version. (A --help option gives you the full story.)

Build a JAR using Gradle

Experimentally, we have a Gradle build that results in a family of JARs, and a POM. This is intended to provide the Jython core in a form that Gradle and Maven users can consume as a dependency. Invoke this with:

PS> .\gradlew publish

and a JAR and POM are delivered to .build2\repo

Whereas the JARs delivered by the installer are somewhat "fat", embedding certain dependencies in shaded (renamed) form, the JARs from the Gradle build are "spare" and cite their dependencies externally through a POM. The project would like to know if this is being done suitably for downstream use.