pywebworker 0.0.6

Python tools for interacting with Web Workers in Pyodide

PyWebWorker

Background

Out-of-the box Pyodide lacks support for a pure Python solution to using web workers. PyWebWorker seeks to fill that gap by providing a set of Python objects and functions to interact with the Web Worker API.

Requirements

The only requirement PyWebWorker imposes, aside from being imported via MicroPip, is that a variable named "pyodide" be in-scope for any scripts executed by pyodide.code.run_js. In order to avoid requiring users to add additional JavaScript files for this module to run, scripts are executed using pyodide.code.run_js during the import process that registers a handful of JavaScript classes used to interface with the Web Worker API as python modules.

It is a goal to eventually remove this, however for the time being it is necessary for any project using this module to have a variable named "pyodide" pointing to the pyodide module in the executing JavaScript. If the Pyodide object is not made available in-scope with this name, this module will not function. See the "examples" folder for demos on how to accomplish this, it is very simple.

Quick Reference

The examples here are valid as of Version 0.0.5

from pywebworker.worker import PyWorker

# This script will print a message to the console when the worker starts and
# will echo back any messages it receives
script = '''
console.log('worker created');
self.onmessage = function(message){
	console.log('Received: ' + message.data);
	self.postMessage(message.data);
}
'''

worker = PyWorker(script)
worker.start()

# the script echos back whatever we send, that message should be ready for us
worker.send_message('This is the first message')
messages = worker.get_unread_messages()

# messages have a .read method so the consumer knows what has and has not been processed
print([message.read() for message in messages])

# the message list can be checked for any unread messages using the has_unread_messages method
worker.send_message('This is the second message')
print(worker.has_unread_messages())

# individual messages can be checked to see if they have been read or not
first_message = worker.get_message(0)
second_message = worker.get_message(1)
print(first_message.is_opened())
print(second_message.is_opened())

# this isn't recommended, but if you really need to check for new messages without using has_unread_messages() or
# get_unread_messages(), _update_messages() will update the messages attribute.
# PLEASE NOTE THAT THIS IS A TEMPORARY WAY TO UPDATE THE LIST, THIS WILL BE REMOVED LATER
worker.send_message('This is the third message')
worker._update_messages()
print(worker.get_message(2).read())

# killing the worker stops it *immediately*. Anything in-progress will be stopped, so only use this when it is certain
# the worker is done and no longer needed!
worker.kill()

Roadmap

This timeline is tentative and subject to change

Version 0.1.0

• PyWorker and JsWorker as objects that run either Python or JavaScript, respectively
• Exception handling for common errors
• Message queues for inbound/outbound messages to the worker
• Enhancements to underlying JavaScript
• Add tests for basic object functions

Version 0.2.0

• Ability to execute scripts from Enscriptem and URI's
• Place JavaScript for underlying JS objects into its own file (as opposed to text in a python module)

Version 0.X.0: Planned near-future but not scheduled

• Ability to pass environment settings to the interpreter in PyWorkers (currently runs on defaults)
• Creation of flexible thread pool for PyWorkers

Version 1.X.0: Mid-importance work, not in immediate plans

• Remove requirement to have Pyodide JavaScript object as in-scope variable named "pyodide"

Known Limitations

PyWorkers are slow to start

Pyodide has to be downloaded and started in each worker thread, which takes time. The goal is to eventually have a pool of threads that download the necessary code on creation and resets the environment between processes. This is a must-have for the near future and will be resolved.

In-scope Pyodide variable in JavaScript Required

Because of the way the package works, the Pyodide object must be an in-scope variable for pyodide.code.run_js. This is not a high-priority issue, however it is something that will be worked on so that it is no longer needed. Suggestions on this are absolutely welcome.