Skip to content
Python Central Hub

Thread Communication (Queue)

Why Queue?

queue.Queuequeue.Queue is thread-safe.

Use it to:

  • pass tasks from producer threads to worker threads
  • avoid manual lock management

Producer-consumer example

queue_example.py
import threading
import queue
import time
 
q = queue.Queue()
 
 
def producer():
    for i in range(5):
        q.put(i)
        print("produced", i)
    q.put(None)  # sentinel
 
 
def consumer():
    while True:
        item = q.get()
        try:
            if item is None:
                break
            print("consuming", item)
            time.sleep(0.2)
        finally:
            q.task_done()
 
 
t1 = threading.Thread(target=producer)
t2 = threading.Thread(target=consumer)
 
t1.start(); t2.start()
 
t1.join()
q.join()  # wait until all tasks are marked done
print("All tasks processed")
queue_example.py
import threading
import queue
import time
 
q = queue.Queue()
 
 
def producer():
    for i in range(5):
        q.put(i)
        print("produced", i)
    q.put(None)  # sentinel
 
 
def consumer():
    while True:
        item = q.get()
        try:
            if item is None:
                break
            print("consuming", item)
            time.sleep(0.2)
        finally:
            q.task_done()
 
 
t1 = threading.Thread(target=producer)
t2 = threading.Thread(target=consumer)
 
t1.start(); t2.start()
 
t1.join()
q.join()  # wait until all tasks are marked done
print("All tasks processed")

Tips

  • Use a sentinel (NoneNone) to stop consumers.
  • Always call task_done()task_done() (often in a finallyfinally).

🧪 Try It Yourself

Exercise 1 – Put and Get

Exercise 2 – Producer-Consumer

Exercise 3 – Queue Size

If this helped you, consider buying me a coffee ☕

Buy me a coffee

Was this page helpful?

Let us know how we did