How to communicate with a running python process from an Objective-C app?

Question

I'm building an Objective-C mac app. I'd like that app to be able to start and continuously communicate with the same running python process.

For example, the basic flow might be:

1. App starts, I start a python process in the background
2. The app imports some libraries and initializes some variables in the python process
3. User does something, I run some python code on this python process using the initialized variables and use the result of the python expression in my mac app

What techniques can I use to accomplish this? Any guidance would be incredibly helpful.

Answer 1

A possible solution is to run a mock web service by your Python process. Define your own interfaces (most likely RESTful APIs) for your Objective-C app to access. Maybe it will be a little expensive in performance - it depends on the complexity of your actual task and the amount of data you want to transfer between the two processes.

For example, in Python process, run a standard HTTP service on 8080 port, listening all the time. Then the Obj-C app send a request to localhost, something like:

http://127.0.0.1:8080/my_service/start_task
http://127.0.0.1:8080/my_service/get_progress
http://127.0.0.1:8080/my_service/get_result

and Python handles that request, do something and return the result in HTTP response.

By the way, maybe you could consider calling Python methods directly by C interface in your Obj-C app rather than run Python scripts in a seperate process.

Answer 2

In my eyes the simplest way to establish communication between two applications is the client-server protocol XMLRPC. Both Cocoa and Python do support it.

The Python part is fairly simple:

import xmlrpc.client
rpcProxy = xmlrpc.client.ServerProxy(URL_OF_SERVER)
rpcProxy.doJobInMacApp(arg1, arg2)

As for the Objective-C-part, I don't know, but it seems to be possible: XML-RPC Server in Cocoa or Best way to use XML-RPC in Cocoa application?