Interprocess communication in Python

Question

What is a good way to communicate between two separate Python runtimes? Thing's I've tried:

• reading/writing on named pipes e.g. os.mkfifo (feels hacky)
• dbus services (worked on desktop, but too heavyweight for headless)
• sockets (seems too low-level; surely there's a higher level module to use?)

My basic requirement is to be able to run python listen.py like a daemon, able to receive messages from python client.py. The client should just send a message to the existing process and terminate, with return code 0 for success and nonzero for failure (i.e. a two-way communication will be required.)

Answer 1

The multiprocessing library provides listeners and clients that wrap sockets and allow you to pass arbitrary python objects.

Your server could listen to receive python objects:

from multiprocessing.connection import Listener  address = ('localhost', 6000)     # family is deduced to be 'AF_INET' listener = Listener(address, authkey=b'secret password') conn = listener.accept() print 'connection accepted from', listener.last_accepted while True:     msg = conn.recv()     # do something with msg     if msg == 'close':         conn.close()         break listener.close() 

Your client could send commands as objects:

from multiprocessing.connection import Client  address = ('localhost', 6000) conn = Client(address, authkey=b'secret password') conn.send('close') # can also send arbitrary objects: # conn.send(['a', 2.5, None, int, sum]) conn.close() 

Answer 2

Nah, zeromq is the way to go. Delicious, isn't it?

import argparse import zmq  parser = argparse.ArgumentParser(description='zeromq server/client') parser.add_argument('--bar') args = parser.parse_args()  if args.bar:     # client     context = zmq.Context()     socket = context.socket(zmq.REQ)     socket.connect('tcp://127.0.0.1:5555')     socket.send(args.bar)     msg = socket.recv()     print msg else:     # server     context = zmq.Context()     socket = context.socket(zmq.REP)     socket.bind('tcp://127.0.0.1:5555')     while True:         msg = socket.recv()         if msg == 'zeromq':             socket.send('ah ha!')         else:             socket.send('...nah')