The changelog describes in plain English the changes that occurred between Py4J
9.1. Py4J 0.10.4
- Release date: October 14th 2016
- Setting a value in a Java array now correctly converts the Python type to
Java type. For example, it is now possible to set a value in a java float
array. Before that change, Python type and Java Array value type had to
- Java side: the serverError callback in the GatewayServerListener is no longer
called when “java.net.SocketException: Socket closed” exception is raised
when the GatewayServer is shutting down. The server_connection_error signal
on the Python side was already ignoring that spurious error.
- tickets closed for 0.10.4 release
9.2. Py4J 0.10.3
- Release date: July 31st 2016
- Python side: Added java_path option in launch_gateway. If None, will detect
whether JAVA_HOME is set and use
JAVA_HOME/bin/java instead of
to launch the JVM.
- Python side: added
True, will launch the JVM in a new process group which (1) prevents signals
sent to the parent Python process to propagate to the child JVM process, and
(2) does not kill the Java process if the Python process dies. This is a
useful option if you want to interrupt a long-running Java method call from
Python and you launched the JVM using launch_gateway. Such interruption has
always been possible if you launched the JVM outside of Python.
- Python side: introduced a small signals library. Users can now connect to
signals emitted by the CallbackServer, which mirrors the events sent by
GatewayServer on the Java side.
- Python side: added
get_java_class function which returns the
java.lang.Class of a JavaClass. Equivalent to calling .class in Java, but
- Python side: fixed the project root setup.py, which allows users to install
Py4J with pip from the git repository. The root setup.py relied on compiled
jars that are no longer provided. It now uses gradlew to build the required
jars during the installation. Works on both Linux and Windows :-)
- Python side: fixed type conversion when passing a large negative integer.
- Java side: added defensive programming to prevent concurrent modification of
the listeners list (in case a listener removes itself after receiving an
- Both sides: added more memory leak tests and fixed a potential memory leak
related to listeners.
- Both sides: added support for IPv6.
- Created an official benchmark program to track Py4J speed. The
results are available as a Google sheet and charts.
- Eclipse: Replaced
Eclipse-BuddyPolicy: global by
* for greater compatibility with other OSGi frameworks.
- tickets closed for 0.10.3 release
9.4. Py4J 0.10.2
- Release date: June 19th 2016
- Both sides: added memory management options to disable garbage collection.
This is useful if you create many short-lived py4j client/server pairs.
- Both sides: fixed ClientServer to allow users to creater multiple
ClientServer instances. Thanks to @jonahkichwacoders for reporting the bug
and helping diagnosing the issue.
- Both sides: it is now possible to specify a python entry point when creating
a CallbackServer. The CallbackClient on the Java side can then access the
python entry point and drive the conversation. See the advanced topics
guide for more information.
- Both sides: fixed memory leak issue with ClientServer and potential deadlock
issue by creating a memory leak test suite.
- Both sides: fixed retry logic by only retrying if an error occurs on write
(send command). Thanks to @jonahkichwacoders for raising the issue.
- Both sides: the assemble gradle task, the Java test suite and the Python test
suite now runs correctly on Windows.
- Java side: added GatewayServerBuilder and ClientServerBuilder to ease the
creation of these instances with many options. Thanks to @jonahkichwacoders.
- A link to the contributing guide now appears when opening pull requests or
- tickets closed for 0.10.2 release
9.5. Py4J 0.10.1
- Release date: May 11th 2016
- Major performance fix: the Python side is now using default buffering when
reading responses from the Java side. This is particularly important if you
transfer large parameters (large strings or byte arrays). A simple benchmark
found that repeatedly sending 10 MB strings went from 99 seconds to 1 second.
Thanks to @kaytwo for finding this bug and suggesting a fix.
- Both the Java and the Python libraries are now available as OSGi bundles.
Thanks to kichwacoders for
funding the work.
- The 0.10.0 jar uploaded to PyPI wrongly required Java 8. The Java
compatibility has been restored to 1.6. Thansk to @agronholm for finding this
- Added the __version__ attribute in the py4j package to conform to PEP396.
Thanks to @lessthanoptimal for reporting this bug.
- tickets closed for 0.10.1 release
9.6. Py4J 0.10.0
- Release date: April 18th 2016
- Added a new threading model that is more efficient with indirect recursion
between Java and Python and that enables users to control which thread will
execute calls. Thanks to kichwacoders for
funding the implementation and providing the initial idea.
- Added TLS support to encrypt the communication between both sides. Thanks to
- Added initial byte stream support so Python can consume Java byte streams
more efficiently. Support is still preliminary and subject to change in the
future, but it provides a good base to build on. See these Python unit test
and Java example class
for a small example. Thanks to @njwhite.
- Java side: converted build script from ant to gradle. Introduced Java coding
conventions and static code analysis. See Java Coding Conventions for more details.
- Java side: it is now possible to build a osgi bundle and an Eclipse update
site from Py4J source. See using Py4J with Eclipse
- tickets closed for 0.10.0 release
9.7. Py4J 0.9.2
- Release date: March 12th 2016
- Python side: added a guard condition in object finalization to prevent
exceptions when the program exits (long standing bug!).
- Java side: Py4J will use the current thread’s classloader instead of the root
classloader to load a class from a fully qualified name. This behavior is
configurable globally in py4j.reflection.ReflectionUtil. thanks to
- Documentation: made a simpler and easier to understand example of callback
(Java calling Python)
- tickets closed for 0.9.2 release
9.8. Py4J 0.9.1
- Release date: January 9th 2016
- Python side: it is now possible to retrieve the listening address and port of
the CallbackServer. This is useful if CallbackServer is bound to port 0.
- Python side: The daemonize_redirect flag is not set to True by default to
preserve backward compatibility prior to 0.9.
- Python side: JavaGateway.shutdown() no longer raises unecessary NoneType
- Python side: if you attempt to access an inexistent object on the Java side,
you will receive a more meaningful exception.
- Python side: the callback server was not correctly closing sockets and it was
possible to leak sockets until no more were available. This has been fixed.
- Java side: the finalization code telling the Python side that it can garbage
collect a python proxy should not longer block (major bug fix).
- Java side: After GatewayServer is launched, it is now possible to
change the address:port where the CallbackClient connects.
- Added a comment in an empty init file so 7zip does not report on error on
Windows (go figure :-) )
- We moved from Travis CI to Circle CI and the automated tests now reliably
- tickets closed for 0.9.1 release
9.9. Py4J 0.9
- Release date: July 25th 2015
- Python side: constructor parameters have been deprecated in favor of
GatewayParameters and CallbackServerParameters. This was necessary because
the number of configuration options is growing fast. Old parameters will be
supported until Py4J 1.0 (at least two more minor versions).
- Python side: IDEs and interactive interpreters such as IPython can now get
help text/autocompletion for Java classes, objects, and members. This makes
Py4J an ideal tool to explore complex Java APIs (e.g., the Eclipse API).
Thanks to @jonahkichwacoders
- Python side: the callback gateway server (necessary for Java to call back
Python functions) can be daemonized and can be started after the main
JavaGateway is started.
- Python side: py4j.java_gateway.launch_gateway has now a cleaner
implementation that discards stdout and stderr output by default. It is also
possible to redirect the output from these channels to separate files,
deques, or queues. Thanks to @davidcsterratt for finding the root cause and
work on the fix.
- It is now possible to install Py4J from git with pip: pip install
- The Eclipse components of Py4J have been moved to another repository. Existing
forks and pull requests can still use the @before-eclipse-split branch until
Py4J reaches 1.0. Fixes won’t be backported to this branch, but pull requests
will be merged by the main maintainer to @master if requested.
- Major cleanup of Python source code to make it fully flake8 (pep8 + pyflakes)
compliant. This should be easier to contribute now.
- Major test cleanup effort to make Python tests more reliable. Testing Py4J is
difficult because there are many versions of Python and Java to test and
Python 2.6 lacks many interesting test features. Effort to make tests even
more robust will continue in the next milestone.
- We introduced a contributing guide and an implicit contributor license
agreement that indicates that anyone contributing to Py4J
keeps the copyright of the contribution but gives a non-revokable right to
license the code using Py4J’s license (3-clause BSD). The copyright statement
has been changed to “Copyright (c) 2009-2015, Barthelemy Dagenais and
individual contributors. All rights reserved.” to make it clear that
individual contributors retain copyrights of their contributions. An
AUTHORS.txt file has been added to the repository to keep track of
contributors: if your name is not in the file and you have contributed to
Py4J, do not hesitate to write on the mailing list or open a pull request.
- Cleaned up the doc that was referring to broken links or refactored classes.
Long-time users may want to review the advanced topics page.
- Added support for Python Wheels.
- We have a new website: https://www.py4j.org
- We have a new blog: https://blog.py4j.org
- Eclipse features have moved to: http://eclipse.py4j.org
- We have a new mailing list.
- github 0.9 milestone
9.10. Py4J 0.8.2.1
- Release date: July 27th 2014
- Fixed a test that used an assert method that does not exist in Python 2.6
9.11. Py4J 0.8.2
- Release date: July 27th 2014
- Fixed constructors not being able to pass proxy (python classes implementing
- Java 6 compatibility was restored in compiled jar file.
- Fixed unit tests for JDK 8
- Added a few extra paths to find_jar_path
- github 0.8.2 milestone
9.12. Py4J 0.8.1
- Release date: December 26th 2013
- Fixed a bug in type inference when interface hierarchy is deeper than
abstract class hierarchy.
- Added a utility method
is_instance_of in py4j.java_gateway to determine
if a JavaObject is an instance of a class.
- Released Py4J in central Maven repository.
- github 0.8.1 milestone
9.13. Py4J 0.8
- Release date: June 15th 2013
- Major fix to the Java byte support. Thanks to @agronholm for spotting
this subtle but major issue and thanks to @fdinto from The Atlantic for
providing a patch!
- Ability to fail early if the py4j.java_gateway.JavaGateway cannot connect to
- Added support for long primitives, BigDecimal, enum types, and inner classes
on the Java side.
- Set saner log levels
- Many small bug fixes and API enhancements (backward compatible).
- Wrote a section in the FAQ about security concerns and precautions with Py4J.
- Added support of Travis-CI and
cleaned up the test suite to remove hardcoded paths.
- github 0.8 milestone
9.14. Py4J 0.7
- Release date: June 2nd 2011
- Major refactoring to support Python 3. Thanks to Alex Grönholm for his
- The build and setup files have been totally changed. Py4J no longer requires
Paver to build and everything is done through ant. The setup.py file only
- Added support for Java byte: byte array are passed by value and converted
to bytearray or bytes.
- Py4J package name changed from Py4J to py4j.
- Bug fixes in the Python callback server and unicode support.
- github 0.7 milestone
9.15. Py4J 0.6
- Release date: February 17th 2011
- Added new exception
Py4JJavaError that enables Python client programs to access
instance of Java exception thrown in the Java client code.
- Improved Py4J setup: no more warnings displayed when installing Py4J.
- Bug fixes and API additions.
- github 0.6 milestone
9.16. Py4J 0.5
- Release date: November 30th 2010
- Added the ability to import packages (e.g.,
- Added support for pattern filtering in
- Added support for automatic conversion of Python collections (list, set,
dictionary) to Java collections. User
an explicit convertor.
- Created two Eclipse features: one embeds the Py4J
Java library. The other
provides a default GatewayServer that is started when Eclipse starts. Both
features are available on the new Py4J Eclipse update site:
- Redesigned the module decomposition of Py4J: there are no more mandatory circular dependencies among modules.
- github 0.5 milestone
9.17. Py4J 0.4
- Release date: September 19th 2010
- Polishing of existing features: fields can be set (not just read), None is accepted as a method parameter, methods are sorted alhabetically in gateway.help(), etc.
- Java Exception Stack Trace are now propagated to Python side.
- Changed interfaces member in Callback classes to implements.
- Internal refactoring to adopt clearer terminology and make Py4J protocol extensible.
- Many bug fixes: most are related to the callback feature.
- github 0.4 milestone
9.18. Py4J 0.3
- Release date: April 27th 2010
- Added support for Java arrays and set.
- Added support for callbacks: Java objects can now call back Python objects.
- Completely redesigned threading and connection model of Py4J to allow multiple threads and callbacks on both side.
- Refactored the memory management to ensure best effort garbage collection.
- github 0.3 milestone
9.19. Py4J 0.2
- Release date: February 11th 2010
- It is now possible to call constructors and reference static members: use the jvm member of a JavaGateway object.
- Java Map is converted to a Python Dictionary.
- Field access is supported through the
get_field function or the
auto_field=True member of JavaGateway.
- Obtain an interactive help page with
- Set is only accessible through the Java Set interface for now.
- Arrays can be referenced, but individual items can only be accessed with this workaround:
- Complete rewrite of the reflection engine on the Java side for more flexibility.
- Improved memory model: no more memory leak caused by Py4J.
- New concurrency model: Py4J is now thread-safe.
- github 0.2 milestone
9.20. Py4J 0.1
- Release date: December 23rd 2009
- This is the first release.
- Basic features like connecting to a JVM and calling methods are implemented.
- Java List is converted to a Python List.
- Field access, constructors, and static classes are NOT accessible yet.
- Dictionary and Set are only accessible through the Java Map and Set interface for now.
- Arrays can be referenced, but individual items cannot be accessed yet.
- github 0.1 milestone