Example of a threaded pipeline in Python.

threaded-pipeline.py

import threading
import queue

class ThreadedWorker():
    def __init__(self):
        self.input_queue = queue.Queue()
        self.output_queue = queue.Queue()
        self.should_exit = False
        self.thread = threading.Thread(target=self.run)
        
    def feed(self, feeder):
        self.input_queue = feeder.output_queue
        return self
    
    def start(self):
        self.thread.start()
        return self
        
    def process(self, value):
        return value
        
    def run(self):
        while not self.should_exit:
            input = self.input_queue.get()
            if input is None:
                break # setinel
            self.output_queue.put(self.process(input))
            
    def stop(self):
        self.should_exit = True
        self.input_queue.put(None) # setinel
        self.thread.join()
        
class AddOne(ThreadedWorker):
    def process(self, value):
        return value + 1
    
add_one_0 = AddOne()
add_one_1 = AddOne().feed(add_one_0)
add_one_2 = AddOne().feed(add_one_1)

add_one_0.start()
add_one_1.start()
add_one_2.start()

add_one_0.input_queue.put(0)
print(add_one_2.output_queue.get())

add_one_0.stop()
add_one_1.stop()
add_one_2.stop()