Python interpreter for Apache Zeppelin
Current interpreter implementation spawns new system python process through
ProcessBuilder and re-directs it's stdin\strout to Zeppelin
To run full suit of tests, including ones that depend on real Python interpreter AND external libraries installed (like Pandas, Pandasql, etc) do
mvn -Dpython.test.exclude='' test -pl python -am
Interpreter environment is setup with thex bootstrap.py It defines
Python 2 or 3 installed with py4j (0.9.2) and matplotlib (1.31 or later) installed on each
Tests only checks the interpreter logic and starts any Python process! Python process is mocked with a class that simply output it input.
Code wrote in
bootstrap_input.pyshould always be Python 2 and 3 compliant.
- Use PEP8 convention for python code.
When interpreter is starting it launches a python process inside a Java ProcessBuilder. Python is started with -i (interactive mode) and -u (unbuffered stdin, stdout and stderr) options. Thus the interpreter has a "sleeping" python process.
Interpreter sends command to python with a Java
outputStreamWiterand read from an
InputStreamReader. To know when stop reading stdout, interpreter sends
print "*!?flush reader!?*"after each command and reads stdout until he receives back the
When interpreter is starting, it sends some Python code (bootstrap.py and bootstrap_input.py) to initialize default behavior and functions (
help(), z.input()...). bootstrap_input.py is sent only if py4j library is detected inside Python process.
Py4J python and java libraries is used to load Input zeppelin Java class into the python process (make java code with python code !). Therefore the interpreter can directly create Zeppelin input form inside the Python process (and eventually with some python variable already defined). JVM opens a random open port to be accessible from python process.
JavaBuilder can't send SIGINT signal to interrupt paragraph execution. Therefore interpreter directly send a
kill SIGINT PIDto python process to interrupt execution. Python process catch SIGINT signal with some code defined in bootstrap.py
Matplotlib figures are displayed inline with the notebook automatically using a built-in backend for zeppelin in conjunction with a post-execute hook.
%python.sqlsupport for Pandas DataFrames is optional and provided using https://github.com/yhat/pandasql if user have one installed