253 lines
8.1 KiB
Python
253 lines
8.1 KiB
Python
__all__ = ('Queue', 'PriorityQueue', 'LifoQueue', 'QueueFull', 'QueueEmpty')
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import collections
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import heapq
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import warnings
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from . import events
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from . import locks
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class QueueEmpty(Exception):
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"""Raised when Queue.get_nowait() is called on an empty Queue."""
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pass
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class QueueFull(Exception):
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"""Raised when the Queue.put_nowait() method is called on a full Queue."""
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pass
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class Queue:
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"""A queue, useful for coordinating producer and consumer coroutines.
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If maxsize is less than or equal to zero, the queue size is infinite. If it
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is an integer greater than 0, then "await put()" will block when the
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queue reaches maxsize, until an item is removed by get().
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Unlike the standard library Queue, you can reliably know this Queue's size
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with qsize(), since your single-threaded asyncio application won't be
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interrupted between calling qsize() and doing an operation on the Queue.
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"""
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def __init__(self, maxsize=0, *, loop=None):
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if loop is None:
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self._loop = events.get_event_loop()
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else:
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self._loop = loop
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warnings.warn("The loop argument is deprecated since Python 3.8, "
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"and scheduled for removal in Python 3.10.",
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DeprecationWarning, stacklevel=2)
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self._maxsize = maxsize
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# Futures.
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self._getters = collections.deque()
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# Futures.
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self._putters = collections.deque()
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self._unfinished_tasks = 0
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self._finished = locks.Event(loop=loop)
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self._finished.set()
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self._init(maxsize)
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# These three are overridable in subclasses.
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def _init(self, maxsize):
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self._queue = collections.deque()
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def _get(self):
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return self._queue.popleft()
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def _put(self, item):
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self._queue.append(item)
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# End of the overridable methods.
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def _wakeup_next(self, waiters):
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# Wake up the next waiter (if any) that isn't cancelled.
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while waiters:
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waiter = waiters.popleft()
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if not waiter.done():
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waiter.set_result(None)
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break
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def __repr__(self):
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return f'<{type(self).__name__} at {id(self):#x} {self._format()}>'
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def __str__(self):
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return f'<{type(self).__name__} {self._format()}>'
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def __class_getitem__(cls, type):
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return cls
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def _format(self):
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result = f'maxsize={self._maxsize!r}'
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if getattr(self, '_queue', None):
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result += f' _queue={list(self._queue)!r}'
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if self._getters:
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result += f' _getters[{len(self._getters)}]'
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if self._putters:
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result += f' _putters[{len(self._putters)}]'
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if self._unfinished_tasks:
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result += f' tasks={self._unfinished_tasks}'
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return result
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def qsize(self):
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"""Number of items in the queue."""
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return len(self._queue)
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@property
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def maxsize(self):
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"""Number of items allowed in the queue."""
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return self._maxsize
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def empty(self):
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"""Return True if the queue is empty, False otherwise."""
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return not self._queue
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def full(self):
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"""Return True if there are maxsize items in the queue.
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Note: if the Queue was initialized with maxsize=0 (the default),
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then full() is never True.
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"""
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if self._maxsize <= 0:
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return False
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else:
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return self.qsize() >= self._maxsize
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async def put(self, item):
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"""Put an item into the queue.
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Put an item into the queue. If the queue is full, wait until a free
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slot is available before adding item.
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"""
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while self.full():
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putter = self._loop.create_future()
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self._putters.append(putter)
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try:
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await putter
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except:
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putter.cancel() # Just in case putter is not done yet.
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try:
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# Clean self._putters from canceled putters.
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self._putters.remove(putter)
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except ValueError:
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# The putter could be removed from self._putters by a
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# previous get_nowait call.
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pass
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if not self.full() and not putter.cancelled():
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# We were woken up by get_nowait(), but can't take
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# the call. Wake up the next in line.
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self._wakeup_next(self._putters)
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raise
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return self.put_nowait(item)
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def put_nowait(self, item):
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"""Put an item into the queue without blocking.
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If no free slot is immediately available, raise QueueFull.
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"""
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if self.full():
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raise QueueFull
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self._put(item)
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self._unfinished_tasks += 1
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self._finished.clear()
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self._wakeup_next(self._getters)
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async def get(self):
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"""Remove and return an item from the queue.
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If queue is empty, wait until an item is available.
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"""
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while self.empty():
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getter = self._loop.create_future()
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self._getters.append(getter)
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try:
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await getter
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except:
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getter.cancel() # Just in case getter is not done yet.
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try:
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# Clean self._getters from canceled getters.
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self._getters.remove(getter)
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except ValueError:
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# The getter could be removed from self._getters by a
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# previous put_nowait call.
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pass
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if not self.empty() and not getter.cancelled():
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# We were woken up by put_nowait(), but can't take
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# the call. Wake up the next in line.
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self._wakeup_next(self._getters)
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raise
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return self.get_nowait()
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def get_nowait(self):
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"""Remove and return an item from the queue.
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Return an item if one is immediately available, else raise QueueEmpty.
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"""
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if self.empty():
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raise QueueEmpty
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item = self._get()
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self._wakeup_next(self._putters)
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return item
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def task_done(self):
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"""Indicate that a formerly enqueued task is complete.
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Used by queue consumers. For each get() used to fetch a task,
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a subsequent call to task_done() tells the queue that the processing
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on the task is complete.
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If a join() is currently blocking, it will resume when all items have
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been processed (meaning that a task_done() call was received for every
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item that had been put() into the queue).
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Raises ValueError if called more times than there were items placed in
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the queue.
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"""
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if self._unfinished_tasks <= 0:
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raise ValueError('task_done() called too many times')
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self._unfinished_tasks -= 1
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if self._unfinished_tasks == 0:
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self._finished.set()
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async def join(self):
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"""Block until all items in the queue have been gotten and processed.
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The count of unfinished tasks goes up whenever an item is added to the
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queue. The count goes down whenever a consumer calls task_done() to
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indicate that the item was retrieved and all work on it is complete.
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When the count of unfinished tasks drops to zero, join() unblocks.
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"""
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if self._unfinished_tasks > 0:
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await self._finished.wait()
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class PriorityQueue(Queue):
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"""A subclass of Queue; retrieves entries in priority order (lowest first).
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Entries are typically tuples of the form: (priority number, data).
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"""
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def _init(self, maxsize):
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self._queue = []
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def _put(self, item, heappush=heapq.heappush):
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heappush(self._queue, item)
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def _get(self, heappop=heapq.heappop):
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return heappop(self._queue)
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class LifoQueue(Queue):
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"""A subclass of Queue that retrieves most recently added entries first."""
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def _init(self, maxsize):
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self._queue = []
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def _put(self, item):
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self._queue.append(item)
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def _get(self):
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return self._queue.pop()
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