asyncio
– 异步 I/O、事件循环、协程和任务
»
Queues:
asyncio queue API was designed to be close to classes of the
queue
模块 (
Queue
,
PriorityQueue
,
LifoQueue
), but it has no
timeout
parameter. The
asyncio.wait_for()
function can be used to cancel a task after a timeout.
asyncio.
队列
(
maxsize=0
,
*
,
loop=None
)
¶
A queue, useful for coordinating producer and consumer coroutines.
若
maxsize
is less than or equal to zero, the queue size is infinite. If it is an integer greater than
0
，那么
yield from put()
will block when the queue reaches
maxsize
, until an item is removed by
get()
.
Unlike the standard library
queue
, you can reliably know this Queue’s size with
qsize()
, since your single-threaded asyncio application won’t be interrupted between calling
qsize()
and doing an operation on the Queue.
此类是 非线程安全 .
3.4.4 版改变：
New
join()
and
task_done()
方法。
empty
(
)
¶
返回
True
若队列为空，
False
否则。
full
(
)
¶
返回
True
若有
maxsize
项在队列中。
注意
If the Queue was initialized with
maxsize=0
(默认)，那么
full()
is never
True
.
get
(
)
¶
Remove and return an item from the queue. If queue is empty, wait until an item is available.
此方法是 协程 .
另请参阅
The
empty()
方法。
get_nowait
(
)
¶
从队列移除并返回项。
返回项若立即可用，否则引发
QueueEmpty
.
join
(
)
¶
Block until all items in the queue have been gotten and processed.
The count of unfinished tasks goes up whenever an item is added to the queue. The count goes down whenever a consumer thread 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.
此方法是 协程 .
3.4.4 版新增。
put
(
item
)
¶
Put an item into the queue. If the queue is full, wait until a free slot is available before adding item.
此方法是 协程 .
另请参阅
The
full()
方法。
qsize
(
)
¶
Number of items in the queue.
task_done
(
)
¶
Indicate that a formerly enqueued task is complete.
Used by queue consumers. For each
get()
用于抓取任务，后续调用
task_done()
tells the queue that the processing on the task is complete.
若
join()
is currently blocking, it will resume when all items have been processed (meaning that a
task_done()
call was received for every item that had been
put()
into the queue).
引发
ValueError
if called more times than there were items placed in the queue.
3.4.4 版新增。
maxsize
¶
队列中允许的项数。
asyncio.
PriorityQueue
¶
子类化的
Queue
; retrieves entries in priority order (lowest first).
Entries are typically tuples of the form: (priority number, data).
asyncio.
QueueEmpty
¶
异常被引发当
get_nowait()
method is called on a
Queue
对象为空。
asyncio.
QueueFull
¶
异常被引发当
put_nowait()
method is called on a
Queue
对象已满。