Asynchronous Method Call in Python

Asynchronous method call in Python?

You can use the multiprocessing module added in Python 2.6. You can use pools of processes and then get results asynchronously with:

apply_async(func[, args[, kwds[, callback]]])

E.g.:

from multiprocessing import Pool

def f(x):
    return x*x

if __name__ == '__main__':
    pool = Pool(processes=1)              # Start a worker processes.
    result = pool.apply_async(f, [10], callback) # Evaluate "f(10)" asynchronously calling callback when finished.

This is only one alternative. This module provides lots of facilities to achieve what you want. Also it will be really easy to make a decorator from this.

How do I call an async function in a new process using multiprocessing?

Here is how you can call an async function in a new process using multiprocessing.
In this code, each request to /webhook creates a new process, which prints apple every 5 seconds.

from __future__ import annotations
import asyncio
from multiprocessing import Process
from fastapi import FastAPI

app = FastAPI()

process_pool: list[Process] = []

async def print_message(fruit):
    print(fruit)

async def loop(fruit):
    while True:
        await print_message(fruit)
        await asyncio.sleep(5)

def run_loop(fruit):
    asyncio.run(loop(fruit))

@app.get("/webhook")
async def webhook():
    print("WEBHOOK RECEIVED")
    fruit = "apple"
    process = Process(target=run_loop, args=(fruit,))
    process_pool.append(process)
    process.start()
    print('done')
    return 'WEBHOOK RECEIVED'

@app.on_event("shutdown")
async def shutdown_event():
    for process in process_pool:
        process.kill()
    for process in process_pool:
        while process.is_alive():
            continue
        process.close()

if __name__ == '__main__':
    print("PROGRAM LAUNCH...")
    print("WEBHOOK RECEIVE READY...")

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