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Write Processing sketches in Python.

Tested on Mac OS 10.8.3, Windows XP, Windows 7, and Ubuntu 12.10.

Quick Start

Download 0200

Then, paste this code into a file, e.g.,

def setup():
    size(600, 400)

def draw():
    ellipse(mouseX, mouseY, 10, 10)

Drag and drop your sketch onto one of these files according to your platform:

If that does not work for you, run the sketch either with the included launcher script (on linux and OS X):

$ ./ path/to/

or using your own Java runtime environment:

$ java -jar processing-py.jar path/to/


To learn check out these resources:

In addition, we are a great fan of learning by doing, and a number of converted examples outline how to use


On Windows use processing-py.bat instead. On Mac OS X, use the processing-py app, or simply drag and drop an example script onto the app.

Using Processing Libraries is implemented in Java, and is meant to be compatible with the existing ecosystem of Processing libraries.

  • Put processing extension libraries in the libraries subdirectory of your installation.

  • Import them in one of the usual Python ways, as in these snippets:

    from peasy import PeasyCam
    # or
    import peasy.PeasyCam
    # or
    import peasy.PeasyCam as PeasyCam

    Unfortunately, from foo import * is not supported.

  • In your setup() method

    cam = PeasyCam(this, 200)

    Many libraries need a reference to "the current PApplet", and that's what this is for.

Included Libraries

Some Processing libraries may not work with right out of the box. In particular, any library that uses Java reflection to call specially-named functions in your sketch will not work. However, we're happy to modify to work with any of the official Processing libraries. Here are the libraries that have required special handling in, and are included in the download:

If you find that some Processing library doesn't work as expected with, please let us know in the bug tracker.


  • How can I create a wrapper?

    Add these lines near the top of your script:

    import launcher
  • How should I load data?

    [Tentative] Along with the launcher, consider using pwd() for file paths. For a given argument it resolves the path for an object relative to the currently running script:

    data = load(pwd("data.txt"))

    In that case, will try to search data.txt always where your script resides.

  • How can I use Ani, or any other library that modifies fields?

    Some libraries such as Ani require you to specify a variable name for animation. Unfortunately they cannot access Python variables directly (and Java's built in classes are immutable).

    To solve this problem we instead create a mutable PrimitiveFloat object. This object has a field .value, which you can use for these purposes.

    import jycessing.primitives.PrimitiveFloat as Float
    x = Float(100.0), 200, "value", 50);  # "value" is the name of the Float's internal field

    In case you need other primitive values, please let us know!

  • I found a bug, what should I do?

    Please report any issue in the bug tracker.

  • Why was this project created?

    I (Jonathan) recently gave a talk about Processing to a group of rather bright 8th-graders, as part of a computer-programming summer camp they were attending at my office. Their curriculum up to that point had been in Python, which is an eminently sensible choice, given the pedagogical roots of the language.

    The kids were really turned on by the demos--I showed them the white glove, and Golan Levin's New Year's cards--but they were bogged down by Processing's C-like syntax, which really seems arcane and unnecessarily complex when you're used to Python.

    I shared my experience with Processing creators Ben Fry and Casey Reas, and they told me that, indeed, the original Processing was a fork of "Design By Numbers", with Python and Scheme support hacked in. Support for a multi-lingual programming environment was always part of the plan, so they were enthusiastic about any new attempt at the problem.

    I was able to hack up a proof of concept in a couple of hours, and have managed to create something worth sharing in a couple of weeks. I was only able to do it at all thanks to the brilliant and beautiful Jython project.

    At the time of Processing's first public release, August of 2001, Jython was too young a project to be used in this way. But now, having done absolutely no work to profile and optimize, I can get hundreds of frames per second of 3D graphics on my linux box. So, kudos to the Processing project, and kudos to Jython!


Written by Jonathan Feinberg <> Launcher & many improvements by Ralf Biedert <>

Also, YourKit, LLC was so kind to sponsor a license for their excellent YourKit Java Profiler. Thank you very much!

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