Subprocess Not Returning Data As Expected

I am using the accepted answer from this question. The relevant code is below. import multiprocessing def query_with_timeout(dbc, timeout, query, *a, **k): conn1, conn2 = multip

Solution 1:

Well, a couple of things based on the code you've posted. First, you don't ever start() the process. But perhaps that's just a mistake you made in typing up this example?

Second, you don't ever send() anything via the connection.

Here's a simplified version of the above with expected behavior:

import multiprocessing
import time

def simple_example(wait, timeout, query):
    conn1, conn2 = multiprocessing.Pipe(False)
    subproc = multiprocessing.Process(target=do_query, args=(wait, query, conn2))
    subproc.start()
    subproc.join(timeout)
    if conn1.poll():
        return conn1.recv()
    subproc.terminate()
    raise Exception('Query %r ran for >%r' % (query, timeout))

def do_query(wait, query, conn):
    print query
    time.sleep(wait)
    conn.send(query)

res = simple_example(0, 2, 'foo')
res = simple_example(3, 2, 'foo')

I fear this may simply be a problem with your example code though.