Pubmarine

Welcome to Pubmarine, a simple pubsub framework for Python-3.5's asyncio.

Pubmarine allows you to code an application using events to communicate between different parts of the program. This gives your program greater flexibility than defining a single API. For instance, if a program has multiple user interfaces to choose from then it will either let some implementation details leak through from the interface layer to the backend or it will have to implement its own abstraction layer for the backend to communicate to the user interface. Pubmarine offers the program the code for that abstraction layer built on top of asyncio so you can have parallelism In IO bound code.

Simple Example

Here's a very simple example to get you started:

#!/usr/bin/python3 -tt

import asyncio
import sys
from pubmarine import PubPen

PY37 = sys.version_info >= (3, 7)

class Server:
    def __init__(self, pubpen):
        self.pubpen = pubpen
        self.beats = 0

    async def heartbeat(self):
        self.pubpen.publish('server_msg', self.beats)
        self.beats += 1
        await asyncio.sleep(1)
        self.pubpen.loop.create_task(self.heartbeat())

class Client:
    def __init__(self, pubpen):
        self.pubpen = pubpen
        self.pubpen.subscribe('server_msg', self.display)

    def display(self, message):
        print(message)

    async def send_message(self):
        for num in range(0, 5):
            print('message: {}'.format(num))
            await asyncio.sleep(2)

async def start():
    if PY37:
        loop = asyncio.get_running_loop()
    else:
        loop = asyncio.get_event_loop()
    pubpen = PubPen(loop)
    server = Server(pubpen)
    client = Client(pubpen)
    await asyncio.wait((client.send_message(), server.heartbeat()))

if __name__ == '__main__':
    if PY37:
        asyncio.run(start())
    else:
        loop = asyncio.get_event_loop()
        loop.run_until_complete(start())

In this example, the server class emits the server_msg event once a second (provided that other coroutines give up control for it to do so.) The client subscribes to the server_msg event and calls the display() method any time that event is emitted. The client also prints a message of its own to the screen to show that both the server and the client coroutines are getting serviced.

Requirements

Pubmarine requires Python-3.5.0 or greater. It does not require anything outside of the Python stdlib to function.

Contributors

Things to know if you're contributing to pubmarine:

Testing Pubmarine

To run the unittests for pubmarine:

python3 -m pip install --user -r test-requirements.txt
python3 -m pip install --user -e .
pytest --cov=pubmarine tests

You can, of course, use a virtualenv instead of --user to install the dependencies.