VOC

A transpiler that converts Python bytecode into Java bytecode.

This is experimental code. If it breaks, you get to keep all the shiny pieces.

What it does:

• Provides an API to let you programmatically create Java class files.
• Compiles a Python 3.4 source file into a Java class file in a nominated package. Supports the conversion of:
  • Class definition and construction
  • Class instantiation
  • Method definition and invocation
  • Some mathematical operations
  • Some operations and methods on primitive types
  • Exception handling
  • for/while/if constructs
  • Identification of mainline entry points
  • Static initialization of modules.
  • List comprehensions
  • Keyword arguments
  • import, from X import Y and from X import * statements for Python code
  • Subclassing Python classes
  • Importing and using native Java APIs
  • Implementing Java interfaces.
  • Extending Java classes.

It doesn't currently support (this list is incomplete):

• Generators
• with statements
• exec() and eval()

These things are all possible - it's just a matter of time and development effort. The order listed here is a rough indicator of development priorities.

Quickstart

Using Python 3.4, install voc, then run it over your python script:

$ pip install voc
$ python -m voc path/to/your/example.py
Creating class 'example'...
Writing example.class...
Done.

This will produce an example.class, in the python namespace, that you can run on any Java 1.7+ VM. To run the classfile, you'll need the Python support libraries. These will eventually be available as a download; for now, you'll need to compile them. See below for compilation instructions.

Once you've got the support Jarfile, you can run the example.class ensuring that the support jarfile is in your classpath. For example, using the Oracle Java VM, you would run:

$ java -XX:-UseSplitVerifier -classpath dist/python-java.jar:. python.example.__init__
Hello, World

The -XX:-UseSplitVerifier argument is necessary to turn off stack map verification in Java 7. This could be addressed by computing stack maps for generated code.

NOTE: if using Java 8 subsitute -XX:-UseSplitVerifier for -noverify as it has be deprecated.

Compiling the support library

Oracle Java

To compile the Python support libraries for Java (the Oracle JVM):

$ ant java

This will create a dist directory that contains python-java.jar.

Android

To compile for Android, you'll need to download the Android SDK. You only need the standalone SDK (see "Other install options") - you don't have to download the fully Android Studio if you don't want to.

Once you've downloaded and installed the SDK, create a local.properties in the top level voc project directory, containing a single line:

sdk.dir=<path to SDK>/sdk

You can then run ant to compile dist/python-android.jar:

$ ant android

You can then add dist/python-android.jar to your Android project.

Documentation

Documentation for VOC can be found on Read The Docs.

Why "VOC"?

The Vereenigde Oostindische Compagnie (VOC), or Dutch East India Company, is often considered the be the world's first multinational corporation. It was also the first company to issue shares, and facilitate the trading of those shares. It was granted a 21 year monopoly to carry out trade activities in Asia, primarily the Spice Islands - the Dutch East Indies. They established a major trading port at Batavia - now Jakarta, on the island of Java (now part of Indonesia). As a result of their monopoly, the VOC became an incredibly valuable company, issuing an 18% annual dividend for almost 200 years.

VOC was... the world's first Enterprise using Java. (rimshot!)

VOC is also a backronym for "Vestigial Output Compiler". Or "Vexing Obtuse Compiler". Or "Valuable Obscure Compiler". Or "Varigated Ocelot Calibrator". It's your choice.

Community

VOC is part of the BeeWare suite. You can talk to the community through:

• @pybeeware on Twitter
• The BeeWare Users Mailing list, for questions about how to use the BeeWare suite.
• The BeeWare Developers Mailing list, for discussing the development of new features in the BeeWare suite, and ideas for new tools for the suite.

Contributing

If you experience problems with VOC, log them on GitHub. If you want to contribute code, please fork the code and submit a pull request.