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cpython/Lib/queue.py /
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| '''A multi-producer, multi-consumer queue.''' | |
| import threading | |
| import types | |
| from collections import deque | |
| from heapq import heappush, heappop | |
| from time import monotonic as time | |
| try: | |
| from _queue import SimpleQueue | |
| except ImportError: | |
| SimpleQueue = None | |
| __all__ = ['Empty', 'Full', 'Queue', 'PriorityQueue', 'LifoQueue', 'SimpleQueue'] | |
| try: | |
| from _queue import Empty | |
| except ImportError: | |
| class Empty(Exception): | |
| 'Exception raised by Queue.get(block=0)/get_nowait().' | |
| pass | |
| class Full(Exception): | |
| 'Exception raised by Queue.put(block=0)/put_nowait().' | |
| pass | |
| class Queue: | |
| '''Create a queue object with a given maximum size. | |
| If maxsize is <= 0, the queue size is infinite. | |
| ''' | |
| def __init__(self, maxsize=0): | |
| self.maxsize = maxsize | |
| self._init(maxsize) | |
| # mutex must be held whenever the queue is mutating. All methods | |
| # that acquire mutex must release it before returning. mutex | |
| # is shared between the three conditions, so acquiring and | |
| # releasing the conditions also acquires and releases mutex. | |
| self.mutex = threading.Lock() | |
| # Notify not_empty whenever an item is added to the queue; a | |
| # thread waiting to get is notified then. | |
| self.not_empty = threading.Condition(self.mutex) | |
| # Notify not_full whenever an item is removed from the queue; | |
| # a thread waiting to put is notified then. | |
| self.not_full = threading.Condition(self.mutex) | |
| # Notify all_tasks_done whenever the number of unfinished tasks | |
| # drops to zero; thread waiting to join() is notified to resume | |
| self.all_tasks_done = threading.Condition(self.mutex) | |
| self.unfinished_tasks = 0 | |
| def task_done(self): | |
| '''Indicate that a formerly enqueued task is complete. | |
| Used by Queue consumer threads. 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 a ValueError if called more times than there were items | |
| placed in the queue. | |
| ''' | |
| with self.all_tasks_done: | |
| unfinished = self.unfinished_tasks - 1 | |
| if unfinished <= 0: | |
| if unfinished < 0: | |
| raise ValueError('task_done() called too many times') | |
| self.all_tasks_done.notify_all() | |
| self.unfinished_tasks = unfinished | |
| def join(self): | |
| '''Blocks 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 the item was retrieved and all work on it is complete. | |
| When the count of unfinished tasks drops to zero, join() unblocks. | |
| ''' | |
| with self.all_tasks_done: | |
| while self.unfinished_tasks: | |
| self.all_tasks_done.wait() | |
| def qsize(self): | |
| '''Return the approximate size of the queue (not reliable!).''' | |
| with self.mutex: | |
| return self._qsize() | |
| def empty(self): | |
| '''Return True if the queue is empty, False otherwise (not reliable!). | |
| This method is likely to be removed at some point. Use qsize() == 0 | |
| as a direct substitute, but be aware that either approach risks a race | |
| condition where a queue can grow before the result of empty() or | |
| qsize() can be used. | |
| To create code that needs to wait for all queued tasks to be | |
| completed, the preferred technique is to use the join() method. | |
| ''' | |
| with self.mutex: | |
| return not self._qsize() | |
| def full(self): | |
| '''Return True if the queue is full, False otherwise (not reliable!). | |
| This method is likely to be removed at some point. Use qsize() >= n | |
| as a direct substitute, but be aware that either approach risks a race | |
| condition where a queue can shrink before the result of full() or | |
| qsize() can be used. | |
| ''' | |
| with self.mutex: | |
| return 0 < self.maxsize <= self._qsize() | |
| def put(self, item, block=True, timeout=None): | |
| '''Put an item into the queue. | |
| If optional args 'block' is true and 'timeout' is None (the default), | |
| block if necessary until a free slot is available. If 'timeout' is | |
| a non-negative number, it blocks at most 'timeout' seconds and raises | |
| the Full exception if no free slot was available within that time. | |
| Otherwise ('block' is false), put an item on the queue if a free slot | |
| is immediately available, else raise the Full exception ('timeout' | |
| is ignored in that case). | |
| ''' | |
| with self.not_full: | |
| if self.maxsize > 0: | |
| if not block: | |
| if self._qsize() >= self.maxsize: | |
| raise Full | |
| elif timeout is None: | |
| while self._qsize() >= self.maxsize: | |
| self.not_full.wait() | |
| elif timeout < 0: | |
| raise ValueError("'timeout' must be a non-negative number") | |
| else: | |
| endtime = time() + timeout | |
| while self._qsize() >= self.maxsize: | |
| remaining = endtime - time() | |
| if remaining <= 0.0: | |
| raise Full | |
| self.not_full.wait(remaining) | |
| self._put(item) | |
| self.unfinished_tasks += 1 | |
| self.not_empty.notify() | |
| def get(self, block=True, timeout=None): | |
| '''Remove and return an item from the queue. | |
| If optional args 'block' is true and 'timeout' is None (the default), | |
| block if necessary until an item is available. If 'timeout' is | |
| a non-negative number, it blocks at most 'timeout' seconds and raises | |
| the Empty exception if no item was available within that time. | |
| Otherwise ('block' is false), return an item if one is immediately | |
| available, else raise the Empty exception ('timeout' is ignored | |
| in that case). | |
| ''' | |
| with self.not_empty: | |
| if not block: | |
| if not self._qsize(): | |
| raise Empty | |
| elif timeout is None: | |
| while not self._qsize(): | |
| self.not_empty.wait() | |
| elif timeout < 0: | |
| raise ValueError("'timeout' must be a non-negative number") | |
| else: | |
| endtime = time() + timeout | |
| while not self._qsize(): | |
| remaining = endtime - time() | |
| if remaining <= 0.0: | |
| raise Empty | |
| self.not_empty.wait(remaining) | |
| item = self._get() | |
| self.not_full.notify() | |
| return item | |
| def put_nowait(self, item): | |
| '''Put an item into the queue without blocking. | |
| Only enqueue the item if a free slot is immediately available. | |
| Otherwise raise the Full exception. | |
| ''' | |
| return self.put(item, block=False) | |
| def get_nowait(self): | |
| '''Remove and return an item from the queue without blocking. | |
| Only get an item if one is immediately available. Otherwise | |
| raise the Empty exception. | |
| ''' | |
| return self.get(block=False) | |
| # Override these methods to implement other queue organizations | |
| # (e.g. stack or priority queue). | |
| # These will only be called with appropriate locks held | |
| # Initialize the queue representation | |
| def _init(self, maxsize): | |
| self.queue = deque() | |
| def _qsize(self): | |
| return len(self.queue) | |
| # Put a new item in the queue | |
| def _put(self, item): | |
| self.queue.append(item) | |
| # Get an item from the queue | |
| def _get(self): | |
| return self.queue.popleft() | |
| __class_getitem__ = classmethod(types.GenericAlias) | |
| class PriorityQueue(Queue): | |
| '''Variant of Queue that retrieves open entries in priority order (lowest first). | |
| Entries are typically tuples of the form: (priority number, data). | |
| ''' | |
| def _init(self, maxsize): | |
| self.queue = [] | |
| def _qsize(self): | |
| return len(self.queue) | |
| def _put(self, item): | |
| heappush(self.queue, item) | |
| def _get(self): | |
| return heappop(self.queue) | |
| class LifoQueue(Queue): | |
| '''Variant of Queue that retrieves most recently added entries first.''' | |
| def _init(self, maxsize): | |
| self.queue = [] | |
| def _qsize(self): | |
| return len(self.queue) | |
| def _put(self, item): | |
| self.queue.append(item) | |
| def _get(self): | |
| return self.queue.pop() | |
| class _PySimpleQueue: | |
| '''Simple, unbounded FIFO queue. | |
| This pure Python implementation is not reentrant. | |
| ''' | |
| # Note: while this pure Python version provides fairness | |
| # (by using a threading.Semaphore which is itself fair, being based | |
| # on threading.Condition), fairness is not part of the API contract. | |
| # This allows the C version to use a different implementation. | |
| def __init__(self): | |
| self._queue = deque() | |
| self._count = threading.Semaphore(0) | |
| def put(self, item, block=True, timeout=None): | |
| '''Put the item on the queue. | |
| The optional 'block' and 'timeout' arguments are ignored, as this method | |
| never blocks. They are provided for compatibility with the Queue class. | |
| ''' | |
| self._queue.append(item) | |
| self._count.release() | |
| def get(self, block=True, timeout=None): | |
| '''Remove and return an item from the queue. | |
| If optional args 'block' is true and 'timeout' is None (the default), | |
| block if necessary until an item is available. If 'timeout' is | |
| a non-negative number, it blocks at most 'timeout' seconds and raises | |
| the Empty exception if no item was available within that time. | |
| Otherwise ('block' is false), return an item if one is immediately | |
| available, else raise the Empty exception ('timeout' is ignored | |
| in that case). | |
| ''' | |
| if timeout is not None and timeout < 0: | |
| raise ValueError("'timeout' must be a non-negative number") | |
| if not self._count.acquire(block, timeout): | |
| raise Empty | |
| return self._queue.popleft() | |
| def put_nowait(self, item): | |
| '''Put an item into the queue without blocking. | |
| This is exactly equivalent to `put(item, block=False)` and is only provided | |
| for compatibility with the Queue class. | |
| ''' | |
| return self.put(item, block=False) | |
| def get_nowait(self): | |
| '''Remove and return an item from the queue without blocking. | |
| Only get an item if one is immediately available. Otherwise | |
| raise the Empty exception. | |
| ''' | |
| return self.get(block=False) | |
| def empty(self): | |
| '''Return True if the queue is empty, False otherwise (not reliable!).''' | |
| return len(self._queue) == 0 | |
| def qsize(self): | |
| '''Return the approximate size of the queue (not reliable!).''' | |
| return len(self._queue) | |
| __class_getitem__ = classmethod(types.GenericAlias) | |
| if SimpleQueue is None: | |
| SimpleQueue = _PySimpleQueue |