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Deephaven fork of jpy Bi-directional Python-Java bridge

Project description

Deephaven jpy

This package is a fork of jpy maintained by Deephaven Data Labs.


  • Note that "deephaven-jpy" is not compatible with "jpy" as they both install shared libraries with the same name.
  • If you already have "jpy" installed, it should be removed before installing "deephaven-jpy"

    # Remove jpy if it is currently installed
    pip uninstall jpy

    # Install deephaven-jpy
    pip install deephaven-jpy


>>> import jpy
>>> ...

jpy Changelog

Version 0.10 (in development)

  • Make jpy work with Anaconda by setting environment variable PYTHONHOME from Java #143. Contribution by Dr-Irv.
  • Fixed: Constants are not properly passed from Java to Python when using interfaces #140. Contribution by Dr-Irv.
  • Fixed: Cannot iterate through a dict in Python 3.x #136. Contribution by Dr-Irv.

Version 0.9

This version includes a number of contributions from supportive GitHub users. Thanks to all of you!


  • Corrected Java reference count of complex PyObject passed back and forth to methods (issue #120). Fix by sbarnoud.
  • Fixed problem where default methods on Java 8 Interfaces were not found (issue #102). Fix by Charles P. Wright.
  • Fixed error caused by missing sys.argv in Python when called from Java (issue #81). Fix by Dave Voutila.
  • Fixed problem where calling jpy.get_type() too many times causes a memory access error (issue #74). Fix by Dave Voutila.
  • Fixed a corruption when retrieving long values (#72). Fix by chipkent.
  • Fixed fatal error when stopping python session (issue #70, #77). Fix by Dave Voutila.

Explicit null checks for avoiding JVM crash (issue #126). Fix by Geomatys.


  • Can now use pip to install Python jpy package directly from GitHub (#83). This works for Linux and OS X where C compilers are available by default and should work on Windows with Visual Studio 15 installed. Contribution by Dave Voutila.
  • Java PyObject is now serializable. Contribution by Mario Briggs.
  • Improved Varargs method matching. You may pass in either an array (as in the past) or individual Python arguments, the match for a varargs method call is the minimum match for each of the arguments. Zero length arrays (i.e. no arguments) are also permitted with a match value of 10.
  • jpy.type_translations dictionary for callbacks when instantiating Python objects.
  • jpy.VerboseExceptions enables full Java stack traces.
  • More Python exceptions are translated to the corresponding Java type.
  • Globals and locals are converted when executing code with PyLib, to allow variables to be used across statement invocation; and interrogated from Java.
  • PyObject wrappers for dictionary, list, and introspection functions to tell you whether or not you can convert the object.
  • Support for isAssignable checks when dealing with Python Strings and primitives, to allow matches for argument types such as java.lang.Comparable or java.lang.Number.

Version 0.8


  • Java interface types don't include methods of extended interfaces (issue #64)
  • Loading of jpy DLL fails for user-specific Python installations on Windows (issue #58)
  • Java interface types didn't expose java.lang.Object methods (issue #57)
  • Java 1-arg static method was confused with a zero-arg non-static method (issue #54)
  • Python interpreter crash occurred when executing del statement on Java arrays (issue #52)
  • Python extensions loaded from Java couldn't see Python symbols (Linux) (issue #38)


  • It is now possible to use jpy Java API to work with multiple Python installations (issue #35). A tool called '' can be used to write configuration files that determine the required shared libraries for a given Python versions. A new Java system property 'jpy.config' is used to point to a desired configuration file.
  • Simplified jpy installation (issue #15):
    • removed need to add JVM path to PATH (Windows) / LD_LIBRARY_PATH (Unix) environment variable
    • removed need to compile Java module using Maven
    • removed need to specify JDK_HOME environment variable, if JAVA_HOME already points to a JDK
  • Added 'jclass' attribute to Python type that wraps a Java class (issue #63) .
  • Java API extensions
  • new methods
  • new method
  • new method
  • new method
  • Java API configuration changes:
    • System property jpy.jpyLib:
    • System property jpy.jdlLib:
    • System property jpy.pythonLib:
    • System property jpy.config:
    • Loaded from

      File ./

      Resource /

      File ${jpy.config}

  • Python API configuration changes:
    • Loaded from

      File ./

      Resource ${jpy-module}/

    • Attribute java_home
    • Attribute jvm_dll
  • Python API extensions
    • new jpyutil module



    • new jpyutil tool

      usage: [-h] [--out OUT] [--java_home JAVA_HOME] [--jvm_dll JVM_DLL]

  • Added basic support for Java Scripting Engine API (issue #53)

Other changes

  • Switched to Apache 2.0 license from version 0.8 and later (issue #60)

Version 0.7.5

  • Fixed bad pointer in C-code which caused unpredictable crashes (issue #43)

Version 0.7.4

  • Fixed a problem where jpy crashes with unicode arguments (issue #42)
  • Fixed segmentation fault occurring occasionally during installation of jpy (issue #40)
  • Improved Java exception messages on Python errors (issue #39)

Version 0.7.3

  • Fixed problem where a Java primitive array argument has occasionally not been initialised by a related Python buffer argument (issue #37)

Version 0.7.2

  • Added backward compatibility with Python 2.7 (issue #34).
  • Added Java parameter annotation 'output' (issue #36). This is used to optimise passing Python buffer arguments where Java primitive arrays are expected.
  • Removed debugging prints of the form "JNI_OnLoad: ..."
  • Corrected documentation of jpy.array(type, init) function, which was said to be jpy.array(type, length)
  • Removed console dumps that occurred when calling from Java proxies into Python
  • Updated Java API documentation and added it to Sphinx doc folder (doc/_static/java-apidoc)
  • Added new diagnostic F_ERR flag to Java class PyLib.Diag
  • Java class PyLib is no longer instantiable

Version 0.7.1

  • Updated README and added after recognising that the distribution misses most of the required source files and learning what to do on this case.

Version 0.7

  • Initial version.

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