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())