mirror of
https://github.com/python/cpython.git
synced 2025-10-31 13:41:24 +00:00
254 lines
7.7 KiB
Python
254 lines
7.7 KiB
Python
"""Queues"""
|
|
|
|
__all__ = ['Queue', 'PriorityQueue', 'LifoQueue', 'QueueFull', 'QueueEmpty']
|
|
|
|
import collections
|
|
import heapq
|
|
|
|
from . import compat
|
|
from . import events
|
|
from . import futures
|
|
from . import locks
|
|
from .coroutines import coroutine
|
|
|
|
|
|
class QueueEmpty(Exception):
|
|
"""Exception raised when Queue.get_nowait() is called on a Queue object
|
|
which is empty.
|
|
"""
|
|
pass
|
|
|
|
|
|
class QueueFull(Exception):
|
|
"""Exception raised when the Queue.put_nowait() method is called on a Queue
|
|
object which is full.
|
|
"""
|
|
pass
|
|
|
|
|
|
class Queue:
|
|
"""A queue, useful for coordinating producer and consumer coroutines.
|
|
|
|
If maxsize is less than or equal to zero, the queue size is infinite. If it
|
|
is an integer greater than 0, then "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.
|
|
"""
|
|
|
|
def __init__(self, maxsize=0, *, loop=None):
|
|
if loop is None:
|
|
self._loop = events.get_event_loop()
|
|
else:
|
|
self._loop = loop
|
|
self._maxsize = maxsize
|
|
|
|
# Futures.
|
|
self._getters = collections.deque()
|
|
# Futures.
|
|
self._putters = collections.deque()
|
|
self._unfinished_tasks = 0
|
|
self._finished = locks.Event(loop=self._loop)
|
|
self._finished.set()
|
|
self._init(maxsize)
|
|
|
|
# These three are overridable in subclasses.
|
|
|
|
def _init(self, maxsize):
|
|
self._queue = collections.deque()
|
|
|
|
def _get(self):
|
|
return self._queue.popleft()
|
|
|
|
def _put(self, item):
|
|
self._queue.append(item)
|
|
|
|
# End of the overridable methods.
|
|
|
|
def _wakeup_next(self, waiters):
|
|
# Wake up the next waiter (if any) that isn't cancelled.
|
|
while waiters:
|
|
waiter = waiters.popleft()
|
|
if not waiter.done():
|
|
waiter.set_result(None)
|
|
break
|
|
|
|
def __repr__(self):
|
|
return '<{} at {:#x} {}>'.format(
|
|
type(self).__name__, id(self), self._format())
|
|
|
|
def __str__(self):
|
|
return '<{} {}>'.format(type(self).__name__, self._format())
|
|
|
|
def _format(self):
|
|
result = 'maxsize={!r}'.format(self._maxsize)
|
|
if getattr(self, '_queue', None):
|
|
result += ' _queue={!r}'.format(list(self._queue))
|
|
if self._getters:
|
|
result += ' _getters[{}]'.format(len(self._getters))
|
|
if self._putters:
|
|
result += ' _putters[{}]'.format(len(self._putters))
|
|
if self._unfinished_tasks:
|
|
result += ' tasks={}'.format(self._unfinished_tasks)
|
|
return result
|
|
|
|
def qsize(self):
|
|
"""Number of items in the queue."""
|
|
return len(self._queue)
|
|
|
|
@property
|
|
def maxsize(self):
|
|
"""Number of items allowed in the queue."""
|
|
return self._maxsize
|
|
|
|
def empty(self):
|
|
"""Return True if the queue is empty, False otherwise."""
|
|
return not self._queue
|
|
|
|
def full(self):
|
|
"""Return True if there are maxsize items in the queue.
|
|
|
|
Note: if the Queue was initialized with maxsize=0 (the default),
|
|
then full() is never True.
|
|
"""
|
|
if self._maxsize <= 0:
|
|
return False
|
|
else:
|
|
return self.qsize() >= self._maxsize
|
|
|
|
@coroutine
|
|
def put(self, item):
|
|
"""Put an item into the queue.
|
|
|
|
Put an item into the queue. If the queue is full, wait until a free
|
|
slot is available before adding item.
|
|
|
|
This method is a coroutine.
|
|
"""
|
|
while self.full():
|
|
putter = self._loop.create_future()
|
|
self._putters.append(putter)
|
|
try:
|
|
yield from putter
|
|
except:
|
|
putter.cancel() # Just in case putter is not done yet.
|
|
if not self.full() and not putter.cancelled():
|
|
# We were woken up by get_nowait(), but can't take
|
|
# the call. Wake up the next in line.
|
|
self._wakeup_next(self._putters)
|
|
raise
|
|
return self.put_nowait(item)
|
|
|
|
def put_nowait(self, item):
|
|
"""Put an item into the queue without blocking.
|
|
|
|
If no free slot is immediately available, raise QueueFull.
|
|
"""
|
|
if self.full():
|
|
raise QueueFull
|
|
self._put(item)
|
|
self._unfinished_tasks += 1
|
|
self._finished.clear()
|
|
self._wakeup_next(self._getters)
|
|
|
|
@coroutine
|
|
def get(self):
|
|
"""Remove and return an item from the queue.
|
|
|
|
If queue is empty, wait until an item is available.
|
|
|
|
This method is a coroutine.
|
|
"""
|
|
while self.empty():
|
|
getter = self._loop.create_future()
|
|
self._getters.append(getter)
|
|
try:
|
|
yield from getter
|
|
except:
|
|
getter.cancel() # Just in case getter is not done yet.
|
|
if not self.empty() and not getter.cancelled():
|
|
# We were woken up by put_nowait(), but can't take
|
|
# the call. Wake up the next in line.
|
|
self._wakeup_next(self._getters)
|
|
raise
|
|
return self.get_nowait()
|
|
|
|
def get_nowait(self):
|
|
"""Remove and return an item from the queue.
|
|
|
|
Return an item if one is immediately available, else raise QueueEmpty.
|
|
"""
|
|
if self.empty():
|
|
raise QueueEmpty
|
|
item = self._get()
|
|
self._wakeup_next(self._putters)
|
|
return item
|
|
|
|
def task_done(self):
|
|
"""Indicate that a formerly enqueued task is complete.
|
|
|
|
Used by queue consumers. For each get() used to fetch a task,
|
|
a subsequent call to task_done() tells the queue that the processing
|
|
on the task is complete.
|
|
|
|
If a 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).
|
|
|
|
Raises ValueError if called more times than there were items placed in
|
|
the queue.
|
|
"""
|
|
if self._unfinished_tasks <= 0:
|
|
raise ValueError('task_done() called too many times')
|
|
self._unfinished_tasks -= 1
|
|
if self._unfinished_tasks == 0:
|
|
self._finished.set()
|
|
|
|
@coroutine
|
|
def join(self):
|
|
"""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 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.
|
|
"""
|
|
if self._unfinished_tasks > 0:
|
|
yield from self._finished.wait()
|
|
|
|
|
|
class PriorityQueue(Queue):
|
|
"""A subclass of Queue; retrieves entries in priority order (lowest first).
|
|
|
|
Entries are typically tuples of the form: (priority number, data).
|
|
"""
|
|
|
|
def _init(self, maxsize):
|
|
self._queue = []
|
|
|
|
def _put(self, item, heappush=heapq.heappush):
|
|
heappush(self._queue, item)
|
|
|
|
def _get(self, heappop=heapq.heappop):
|
|
return heappop(self._queue)
|
|
|
|
|
|
class LifoQueue(Queue):
|
|
"""A subclass of Queue that retrieves most recently added entries first."""
|
|
|
|
def _init(self, maxsize):
|
|
self._queue = []
|
|
|
|
def _put(self, item):
|
|
self._queue.append(item)
|
|
|
|
def _get(self):
|
|
return self._queue.pop()
|
|
|
|
|
|
if not compat.PY35:
|
|
JoinableQueue = Queue
|
|
"""Deprecated alias for Queue."""
|
|
__all__.append('JoinableQueue')
|