How to run multiple instances of an object with two threads inside each object?

Question

I'm trying to wrap two threaded functions inside an object and run a couple of instances of the object. So far I could only run the objects if I pull the threading outside the class.

import threading

class MyObject:
    
    def __init__(self, item_id):
        self.item_id = item_id

    def func_one(self):
        # do stuff

    def func_two(self):
        # do another thing

# initialize objects
obj1 = MyObject("item-01")
obj2 = MyObject("item-02")

# create threads for each object
thread1_obj1 = threading.Thread(target=obj1.func_one)
thread2_obj1 = threading.Thread(target=obj1.func_two)
thread1_obj2 = threading.Thread(target=obj2.func_one)
thread2_obj2 = threading.Thread(target=obj2.func_two)

# start and join threads
thread1_obj1.start()
thread2_obj1.start()
thread1_obj2.start()
thread2_obj2.start()

thread1_obj1.join()
thread2_obj1.join()
thread1_obj2.join()
thread2_obj2.join()

Is there a way to encapsulate the threads inside the class instead of pulling them out to run the the objects?

Style note: Your thread1_obj1 variable and your thread1_obj2 variables refer to different threads, but they both have "thread1" in their names. In an enterprise-grade software engineering project, a code reviewer probably would ask you to change their names. E.g.; thread1_obj1, thread2_obj2, thread3_obj1, and thread4_obj2. — Solomon Slow
– Solomon Slow, Commented Feb 7, 2024 at 19:17

Barmar · Accepted Answer · 2024-02-07 18:21:56Z

1

Define a method in the class that runs both functions, each in its own thread. Then call that method from the main thread.

import threading

class MyObject:
    
    def __init__(self, item_id):
        self.item_id = item_id

    def func_one(self):
        # do stuff

    def func_two(self):
        # do another thing

    def run_threads(self):
        self.thread1 = threading.Thread(target=self.func_one)
        self.thread2 = threading.Thread(target=self.func_two)
        self.thread1.start()
        self.thread2.start()

    def join_threads(self):
        self.thread1.join()
        self.thread2.join()

obj1 = MyObject("item-01")
obj2 = MyObject("item-02")

obj1.run_threads()
obj2.run_threads()

obj1.join_threads()
obj2.join_threads()

answered Feb 7, 2024 at 18:21

Barmar

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1 Comment

R.Orteza Over a year ago

Thank you! This does encapsulate the threads inside the object and can run multiple instances of the object!

R.Orteza · Accepted Answer · 2024-02-07 18:27:52Z

I figured it out. Here's the way to encapsulate the threads inside the class:

import threading

class MyObject:
    
    def __init__(self, item_id):
        self.item_id = item_id
        self.t1 = threading.Thread(target=self.func_one)
        self.t2 = threading.Thread(target=self.func_two)
    
    def thread_start(self):
        self.t1.start()
        self.t2.start()
    
    def thread_join(self):
        self.t1.join()
        self.t2.join()

    def func_one(self):
        # do stuff

    def func_two(self):
        # do another thing

# initialize objects
obj1 = MyObject("item-01")
obj2 = MyObject("item-02")

# run and join objects' threads
obj1.thread_start()
obj2.thread_start()
obj1.thread_join()
obj2.thread_join()

Mark Tolonen · Accepted Answer · 2024-02-07 18:39:35Z

To completely encapsulate, __init__ can create and start each thread and a join method can stop them. Using __enter__ and __exit__ the class instances can be used with with to automatically stop the threads when the objects go out-of-scope:

import threading
import time

class MyObject:

    def __init__(self, item_id):
        self.item_id = item_id
        self.thread1 = threading.Thread(target=self.func_one, daemon=True)
        self.thread2 = threading.Thread(target=self.func_two, daemon=True)
        self.running = True
        self.thread1.start()
        self.thread2.start()

    def func_one(self):
        while self.running:
            print(f'{self.item_id} func_one')
            time.sleep(1)

    def func_two(self):
        while self.running:
            print(f'{self.item_id} func_two')
            time.sleep(1)

    def join(self):
        self.running = False
        self.thread1.join()
        self.thread2.join()

    def __enter__(self):
        return self

    def __exit__(self, exec_type, exc_val, exc_tb):
        self.join()

with MyObject("item-01") as obj1, MyObject('item-02') as obj2:
    time.sleep(3)

Output:

item-01 func_one
item-01 func_two
item-02 func_one
item-02 func_two
item-01 func_one
item-02 func_two
item-02 func_one
item-01 func_two
item-01 func_one
item-01 func_two
item-02 func_two
item-02 func_one
item-01 func_one
item-01 func_two

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