GeezerVison is showing github.com — Processing 4 in Python mode Sound Library not working · Issue #1588 · processing/processing4
Processing 4 in Python mode Sound Library not working #1588
Description
Most appropriate sub-area of Processing 4?
I'm not sure
Processing version
4.5.7 (but really every version since 4 came out)
Operating system
MacOS Tahoe 26.7.1
Bug description
I get the following error when starting a project that uses the Sound Library:
java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
at jycessing.LibraryImporter.addJarToClassLoader(LibraryImporter.java:315)
at jycessing.LibraryImporter.recursivelyAddJarsToClasspath(LibraryImporter.java:164)
at jycessing.LibraryImporter.addLibrary(LibraryImporter.java:140)
at jycessing.LibraryImporter$1.call(LibraryImporter.java:82)
at org.python.core.PyObject.call(PyObject.java:480)
at org.python.core.PyObject.call(PyObject.java:484)
at org.python.pycode._pyx11.f$0(MicCheck.pyde:1)
at org.python.pycode._pyx11.call_function(MicCheck.pyde)
at org.python.core.PyTableCode.call(PyTableCode.java:171)
at org.python.core.PyCode.call(PyCode.java:18)
at org.python.core.Py.runCode(Py.java:1614)
at org.python.core.Py.exec(Py.java:1658)
at org.python.pycode._pyx10.f$0(/Users/Joey/Desktop/MicCheck/MicCheck.pyde:96)
at org.python.pycode._pyx10.call_function(/Users/Joey/Desktop/MicCheck/MicCheck.pyde)
at org.python.core.PyTableCode.call(PyTableCode.java:171)
at org.python.core.PyCode.call(PyCode.java:18)
at org.python.core.Py.runCode(Py.java:1614)
at org.python.core.Py.exec(Py.java:1658)
at org.python.util.PythonInterpreter.exec(PythonInterpreter.java:276)
at jycessing.PAppletJythonDriver.processSketch(PAppletJythonDriver.java:233)
at jycessing.PAppletJythonDriver.findSketchMethods(PAppletJythonDriver.java:613)
at jycessing.Runner.runSketchBlocking(Runner.java:399)
at jycessing.mode.run.SketchRunner.lambda$2(SketchRunner.java:112)
at java.base/java.lang.Thread.run(Thread.java:840)
Hmm. Can't load native code to bring window to front using the absolute path: /Users/Joey/Documents/Processing/modes/PythonMode/mode/libjniosx.dylib.
Hmm. Can't load native code to bring window to front.
Steps to reproduce this
-
Open the MicCheck project (zip file provided in snippet section)
-
Run the code
-
I get the error message listed in the Bug Description section.
snippet
MicCheck.zip
Additional context
The Sound Library using Python mode has never work in any version of Processing 4.
Would you like to work on the issue?
No, I’m just reporting the issue
Activity
SableRaf commented on Oct 23, 2026
Hi @jcarlis1, and thanks for reporting this!
Although a version of Python Mode was released for Processing 4, development stopped before it was fully functional, and the project is no longer maintained.
An alternative is being developed, but in the meantime, we recommend using py5.
You can find more information here: Status of Python Mode for Processing
cc @catilac
hx2A commented on Oct 23, 2026
py5 uses CPython and connects Python to Java using the library JPype. py5 has nice features for making it easy to work with Processing's Java extension libraries. You'd be able to download the library using the download_library() function:
https://py5coding.org/reference/py5tools_processing_download_library.html
And then after importing py5 you can import the Sound library classes just as you would import a Python class.
If you want to try py5 I can make a simple sound example for you if you like; let me know how much assistance you need.
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