Python Queue Module Explained: Thread-Safe Queue Classes

Python's queue module provides thread-safe queue classes for safe data sharing between threads.

In multithreaded programming, using global variables can cause race conditions; queues simplify synchronization.

The module offers several queue types: Queue (FIFO), LifoQueue (LIFO), and PriorityQueue.

Key methods include put(), get(), task_done(), join(), qsize(), empty(), full(), put_nowait(), get_nowait().

Examples demonstrate basic usage, bounded queues with maxsize, handling full/empty exceptions, and producer-consumer patterns.

import queue import threading import time def producer(q): for i in range(5): q.put(i) print(f'Produced {i}') time.sleep(0.1) q.put(None) # sentinel def consumer(q): while True: item = q.get() if item is None: break print(f'Consumed {item}') q.task_done() q = queue.Queue() t1 = threading.Thread(target=producer, args=(q,)) t2 = threading.Thread(target=consumer, args=(q,)) t1.start() t2.start() t1.join() t2.join() q.join() print('All tasks completed')

Additional examples show put_nowait/get_nowait and handling Full and Empty exceptions:

import queue q = queue.Queue(maxsize=2) try: q.put_nowait(1) q.put_nowait(2) q.put_nowait(3) # raises Full except queue.Full: print('Queue is full') while not q.empty(): print(q.get())