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Jython: Python for the Java Platform (TigerJython Edition)

This is the TigerJython version of Jython that includes some (non-standard) modifications. In particular, these modifications include:

  • Emulation of Python 3 syntax and behaviour: This emulation of Python 3 behaviour is rather limited and superficial. This is not Jython 3! However, TigerJython is an educational environment, and our aim is to backport enough of Python 3 so that beginners can start with current syntax until a full Jython 3 version becomes ready.

    • Internally, strings are mostly unicode—although we did not replace all occurrences of PyString by PyUnicode. Hopefully, this will also finally solve the old issue of running Jython on systems where paths can comprise unicode characters.
    • Likewise, longs are output without the trailing L and identify as ints.
    • Some builtin functions are replaced, i.e. range is the same as xrange in Jython.

  • Added fields and properties: Sequences have additional properties .head and .tail to easily access the first element of a sequence or the remainder, respectively. Additionally, lists also support fully writable properties .first and .last to access (and change) the first or last element of the list, respectively. .first and .head are synonyms, of course, except that .head is read-only whereas del mylist.first will work.

  • Additional/Modified builtins: Besides the modifications that are indicated by Python 3-emulation (see above), we also added some builtin functions and types. Most prominently, input() behaves differently in that it is somewhere inbetween Python 2 and Python 3 behaviour: if the entered string is a number, the returned type is an int or float, respectively, whereas other strings are returned as str.

  • Repeat-loop: There is an additional loop construct using the keyword repeat. You enable it by using from __future__ import repeat_loop. It then allows you to say repeat n: suite, where n is the number of desired iterations.

  • print/repeat detection: Before properly parsing your program, it will be scanned to detect whether you are using print as a statement or as a function. Likewise, it will also try to discover the use of repeat. This is not a failsafe method, but aimed at TigerJython's use case where most programs use print as a function and use repeat as a loop. At the same time we need to fully support the entire existing library, which does neither.

  • Roadmap/Plans for future extensions: Switching to the new Python 3 parser, bringing full support for Python 3 syntax. This will also allow for type annotations (although they will be ignored by the compiler/interpreter).

Original Readme

This is the development repository of Jython, the implementation of Python in Java. Only version 2.7 of Python can be supported at present (but watch this space for a 3.x version).

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: https://www.youtube.com/watch?v=hLm3garVQFo

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 Git for version-control, and the master repository is at https://github.com/jython/jython, You should clone this repository to create a buildable copy of the latest state of the Jython source. The previously authoritative repository at https://hg.python.org/jython is not now in use, remaining frozen at v2.7.2.

Build using ant for development

Jython is normally built using ant. It is necessary to have Ant and at least a Java 8 SDK on the path. To build Jython in development, we generally use the command:

ant

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

dist/bin/jython

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 JAR from the Gradle build is "spare" and cites its dependencies externally through a POM. The project would like to know if this is being done suitably for downstream use.