Tutorial 0 - Hello, world!¶
In this tutorial, you’ll take a really simple “Hello, world!” program written in Python, convert it into a classfile, and run it on the Java Virtual Machine.
Setup¶
This tutorial assumes you’ve read and followed the instructions in Installation. If you’ve done this, you should have:
- Java 7 (or higher) installed and available on your path,
- An
env
directory for your virtualenv - A
tutorial
directory with a VOC checkout, - An activated Python 3.4+ virtual environment,
- VOC installed in that virtual environment,
- A compiled VOC support library.
Start a new project¶
Let’s start by creating a tutorial0
directory in the tutorial directory alongside the voc
directory you just cloned into:
$ mkdir tutorial0
$ cd tutorial0
So that your directory structure looks like:
tutorial
├── env
├── ouroboros
├── tutorial0
└── voc
Then create a file called example.py
in this tutorial0
directory.
Add the following Python code to example.py
:
print("Hello World!")
Save the file. Run VOC over this file, compiling the Python code into a Java class file:
$ voc -v example.py
This runs the VOC compiler over the example.py
source file. The -v
flag
asks VOC to use verbose output so you can see what is going on.
You will see output like the following:
Compiling example.py ...
Writing python/example.class ...
This will produce an example.class
in the python
namespace.
This classfile can run on any Java 6 (or higher) VM. To run the project, type:
- On Linux / OS X
$ java -classpath ../voc/dist/python-java-support.jar:. python.example
Hello World!
- On Windows
> java -classpath ../voc/dist/python-java-support.jar;. python.example
Hello World!
Congratulations! You’ve just run your first Python program under Java using VOC! Now you’re ready to get a little more adventurous.