Py4J - A Bridge between Python and Java

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# 1. Installing Py4J

## 1.1. Installing Python 2.6+ or 3.6

Py4J is a library written in Python and Java. Currently, Py4J has been tested with Python 2.6, 2.7, 3.4, 3.5, and 3.6 but it should also be compatible with Python 3.3. You can install Python by going to the official Python download page.

## 1.2. Installing Java 6+

You also need to install a Java environment, version 6 (7 and 8 are also supported). You can install a Java environment by going to the official Java download page You will need to download the JDK if you plan to use the Java compiler, but you only need the JRE if you are using another compiler, such as the one provided by the Eclipse Development Environment.

## 1.3. Installing Py4J

There are three ways to install Py4J:

### 1.3.1. Using easy_install or pip

1. Run `pip install py4j` or `easy_install py4j` (don’t forget to prefix with sudo if you install Py4J system-wide on a *NIX operating system).
2. Py4J should now be in your PYTHONPATH.
3. The Py4J Java library is located in `share/py4j/py4j0.x.jar`. The exact location depends on the platform and the installation type. Some likely locations are:
   1. Either `/usr/share/py4j/py4j0.x.jar` or `/usr/local/share/py4j/py4j0.x.jar` for system-wide install on Linux.
   2. `{virtual_env_dir}/share/py4j/py4j0.x.jar` for installation in a virtual environment.
   3. `C:\python27\share\py4j\py4j0.x.jar` for system-wide install on Windows.

### 1.3.2. Using an official release

1. Download the latest official release from from PyPI. If you are using a *NIX OS, download the tar.gz file. If you are using Windows, download the zip file.
2. Untar/Unzip the file and navigate to the newly created directory, e.g., `cd py4j-0.x`.
3. Run `python setup.py install` (don’t forget to prefix with sudo if you install Py4J system-wide).
4. Py4J should now be in your PYTHONPATH.
5. The Py4J Java library is located under `py4j-java/py4j0.x.jar`. Add this library to your classpath when using Py4J in a Java program.

### 1.3.3. Using the latest development source code

You can install the latest version with pip and git: `pip install git+https://github.com/bartdag/py4j.git`

Otherwise, to build the Java and Python libraries, you need:

1. Git to download the latest source code. Execute the command line `git clone https://github.com/bartdag/py4j.git py4j` to download the source code.
2. Gradle to build the Py4J Java library execute the command line `./gradlew assemble` in the py4j-java project directory to build the code and create a jar file. The jar file you are looking for is `py4j-java/py4jXYZ.jar` where XYZ is the current version of Py4J.
3. Sphinx to build the documentation. Just execute the command `make html` in the py4j-web directory.
4. Libraries such as nose to test the Py4J Python library. Just run `pip install -r requirements.txt` in py4j directory.

Here are a few useful commands to build Py4J:

1. `cd py4j-java; ./gradlew buildPython` - builds the Py4J Java library in a jar, the documentation, and the Python binary and source distributions. The source and wheel distributions will be in `py4j-python/dist` directory (e.g., `py4j-python/dist/py4j-0.10.0.tar.gz`).
2. `cd py4j-java; ./gradlew bundles` - builds the Py4J Java Library as a OSGi bundle (in build/plugins).
3. `cd py4j-java; ./gradlew updateSite` - builds the Eclipse update site (in build/updatesite).
4. `cd py4j-java; ./gradlew check` - runs Java tests, FindBugs, and Java coding conventions checks. (Python checks will be added in the future).
5. `cd py4j-python; flake8` - performs flake8 check on Python source code.
6. `cd py4j-python; nosetests` - runs Python test suite.

### 1.3.4. Maven install

1. Download the source code as explained above.
2. Go to the py4j-java directory and execute `mvn install`.
3. Alternatively, if a test fails (possible because of sockets), execute `mvn -Dmaven.test.skip=true install`
4. Builded binaries will be in the directory `target/py4j-0.x.jar`.

### Questions/Feedback?

- Try the FAQ -- It answers many questions.
- Search for information in the archives of the py4j-users mailing list, or post a question.
- If you notice errors with this documentation, open a ticket and let us know. Please, only open a ticket for feedback or improvements on the docs. To get help, use the links above!
- Request professional services to get a custom feature implemented quickly or to receive commercial support.

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