pytalk.js

Pytalk is a module for bidirectional communication between Node and Python.

It lets you create Python process, and communicate with it via standard streams. Every message passed through pytalk gets serialized into JSON. Before starting the process, Pytalk modifies the Python code, instantiating an event loop and allowing you to send and recieve messages with pytalk_emit, pytalk_on or registering Python method with pytalk_method.

Install

Install through npm

npm install pytalk

Usage

1. Using a worker script, calling registered Python method asynchronously

index.js                                      |  worker.py
------------------------------------------------------------------------------------------------
const pytalk = require('pytalk');             |  import cv2
                                              |  import uuid
                                              |  
let worker = pytalk.worker('worker.py');      |  @pytalk_method('blur')
let blur = worker.method('blur');             |  def cv2blur(path):
                                              |      img = cv2.blur(cv2.imread(path), (20, 20))
blur('image.jpg', (err, blurred) => {         |      dst = str(uuid.uuid1()) + '.jpg'
  console.log(`Saved to ${blurred}`);         |      cv2.imwrite(dst, img)
});                                           |      return dst

2. Importing modules using proxy PyObjects.

const pytalk = require('pytalk');

let worker = pytalk.worker();      // Create Python process

let math = worker.import('math')   // Load modules
  , os   = worker.import('os')
  , np   = worker.import('numpy');

math.factorial(10)                 // 3628800
os.path.split('aaa/bbb')           // ['aaa', 'bbb']


let arr = np.array([4, 9, 16])     // PyObject instance
arr = np.sqrt(arr)                 // still PyObject instance
arr.tolist()                       // [2, 3, 4]

Note that objects proxied by PyObjects don't get garbage collected by Python. You can unreference them manually using unrefAll().

Documentation

#####new Worker([scriptPath], [options]) or, which is the same pytalk.worker(scriptPath, options)

scriptPath

path to the Python script.

options

• pythonPath - path to the Python binary. Default is python.
• stdout - callback called when Python script prints something. Default is console.log.
• stderr - callback called on Python's raised errors. Default is console.log.
• async - If true, PyObject's methods become async. Default is false. (example)

#####Worker.method(methodName) Returns a function(arg1, ..., argN, callback). args are the args passed to the Python method, registered using @pytalk_method(methodName) decorator. callback is a error-first function, called when Python method finishes its work. Use this when you need async version of some sync Python function.

#####Worker.methodSync(methodName) Same thing as Worker.method, except it waits until Python method gets its work done, and returns whatever Python function returns. Uses deasync under the hood.

#####Worker.on(eventName, callback) Registers event handler for eventName. callback gets triggered with (err, args) passed every time pytalk_emit(eventName, args) is called in Python code.

#####Worker.emit(eventName, ...args) Calls Python function, registered with @pytalk_on(eventName) decorator, or through pytalk_on(eventName, callback)

#####Worker.close() Sends exitSignal to Python's event loop. Worker closes as soon as it finishes its current job.

#####Worker.unrefAll() Removes all references to Python objects, proxied by JavaScript objects. This allows Python GC to free resources if it needs to.

#####Worker.import(moduleName) Imports moduleName in Python, and returns a proxy PyObject.

License

MIT