队列 ¶

asyncio 队列的设计类似于类在 queue 模块。尽管 asyncio 队列不是线程安全的，但它们是为用于 async/await 代码专门设计的。

注意，asyncio 队列的方法没有 timeout 参数；使用 asyncio.wait_for() 函数采用超时做队列操作。

另请参阅范例以下章节。

队列 ¶

class asyncio. 队列 ( maxsize = 0 ) ¶

FIFO (先进先出) 队列。

若 maxsize is less than or equal to zero, the queue size is infinite. If it is an integer greater than 0 ，那么 await put() blocks when the queue reaches maxsize until an item is removed by get() .

不像标准库线程化 queue , the size of the queue is always known and can be returned by calling the qsize() 方法。

3.10 版改变：移除 loop 参数。

此类是非线程安全 .

maxsize ¶: 队列中允许的项数。

empty ( ) ¶: 返回 True 若队列为空， False 否则。

full ( ) ¶

返回 True 若有 maxsize 项在队列中。

若队列被初始化采用 maxsize=0 (默认)，那么 full() 从不返回 True .

协程 get ( ) ¶

Remove and return an item from the queue. If queue is empty, wait until an item is available.

引发 QueueShutDown if the queue has been shut down and is empty, or if the queue has been shut down immediately.

get_nowait ( ) ¶: 返回项若立即可用，否则引发 QueueEmpty .

协程 join ( ) ¶

Block until all items in the queue have been received and processed.

The count of unfinished tasks goes up whenever an item is added to the queue. The count goes down whenever a consumer coroutine calls task_done() to indicate that the item was retrieved and all work on it is complete. When the count of unfinished tasks drops to zero, join() unblocks.

协程 put ( item ) ¶

Put an item into the queue. If the queue is full, wait until a free slot is available before adding the item.

引发 QueueShutDown if the queue has been shut down.

put_nowait ( item ) ¶

将项不阻塞放入队列。

若没有立即可用的空闲槽，引发 QueueFull .

qsize ( ) ¶: 返回队列中的项数。

shutdown ( immediate = False ) ¶

Shut down the queue, making get() and put() raise QueueShutDown .

默认情况下， get() on a shut down queue will only raise once the queue is empty. Set immediate to true to make get() raise immediately instead.

All blocked callers of put() and get() will be unblocked. If immediate is true, a task will be marked as done for each remaining item in the queue, which may unblock callers of join() .

3.13 版添加。

优先队列 ¶

class asyncio. PriorityQueue ¶

A variant of Queue ; retrieves entries in priority order (lowest first).

Entries are typically tuples of the form (priority_number, data) .

LIFO (后进先出) 队列 ¶

class asyncio. LifoQueue ¶: A variant of Queue that retrieves most recently added entries first (last in, first out).

异常 ¶

exception asyncio. QueueEmpty ¶: 此异常被引发当 get_nowait() 方法被空队列所调用。

exception asyncio. QueueFull ¶: 异常被引发当 put_nowait() method is called on a queue that has reached its maxsize .

exception asyncio. QueueShutDown ¶

Exception raised when put() or get() is called on a queue which has been shut down.

3.13 版添加。

范例 ¶

Queue 可以用于在几个并发任务之间分发工作量：

import asyncio import random import time async def worker(name, queue): while True: # Get a "work item" out of the queue. sleep_for = await queue.get() # Sleep for the "sleep_for" seconds. await asyncio.sleep(sleep_for) # Notify the queue that the "work item" has been processed. queue.task_done() print(f'{name} has slept for {sleep_for:.2f} seconds') async def main(): # Create a queue that we will use to store our "workload". queue = asyncio.Queue() # Generate random timings and put them into the queue. total_sleep_time = 0 for _ in range(20): sleep_for = random.uniform(0.05, 1.0) total_sleep_time += sleep_for queue.put_nowait(sleep_for) # Create three worker tasks to process the queue concurrently. tasks = [] for i in range(3): task = asyncio.create_task(worker(f'worker-{i}', queue)) tasks.append(task) # Wait until the queue is fully processed. started_at = time.monotonic() await queue.join() total_slept_for = time.monotonic() - started_at # Cancel our worker tasks. for task in tasks: task.cancel() # Wait until all worker tasks are cancelled. await asyncio.gather(*tasks, return_exceptions=True) print('====') print(f'3 workers slept in parallel for {total_slept_for:.2f} seconds') print(f'total expected sleep time: {total_sleep_time:.2f} seconds') asyncio.run(main())

队列 ¶

队列 ¶

优先队列 ¶

LIFO (后进先出) 队列 ¶

异常 ¶

范例 ¶

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