Python multiprocessing pool.apply_async() result access via result.get() throws TypeError: object is not callable

Question

I want to use the return value of an object's method within the multiprocessing module. From the documentation I thought that this can be realized by multiprocessing.pool.AsyncResult.get .

But instead, an error is thrown in my case whereas normally an integer value should be returned.

Here's a minimal example:

import multiprocessing as mp
from random import randrange


class Model():
    def __init__(self):
        self.rno = randrange(100)

    def solve(self, *args, **kwargs):
        print(args, kwargs)
        return self.rno


if __name__ == '__main__':

    # sample data
    models = [Model() for m in range(0, 10)]
    args = [1, 2]
    kwds = {'foo': 3, 'bar': 4}

    # execution
    pool = mp.Pool(processes=mp.cpu_count())
    for m in models:
        result = pool.apply_async(m.solve(*args, **kwds))
        print(result.get())
    pool.close()
    pool.join()

Instead of delivering the attribute rno of the object result.get() throws an error TypeError: 'int' object is not callable .

Any hints? What am I missing here?

Thanks in advance for your help!

PS: Note that in my real application the return value of the method solve() delivers another data type whereas the structure changes dynamically. But it looks if I am generally missing something..

Answer 1

I found the solution on my own!

The error was that I have passed the result of the method to pool but not the function itself.

Here's a working example:

import multiprocessing as mp
from random import randrange


class Model():
    def __init__(self):
        self.rno = randrange(100)

    def solve(self, *args, **kwargs):
        print(args, kwargs)
        return [self.rno, args, kwargs]


if __name__ == '__main__':

    # sample data
    models = [Model() for m in range(0, 10)]
    args = [1, 2]
    kwds = {'foo': 3, 'bar': 4}

    pool = mp.Pool(processes=mp.cpu_count())
    for m in models:
        result = pool.apply_async(m.solve, args=args, kwds=kwds)
        print(result.get())
    pool.close()
    pool.join()

Sorry for bothering you..