1 '''A multi-producer, multi-consumer queue.'''
2
3 import threading
4 import types
5 from collections import deque
6 from heapq import heappush, heappop
7 from time import monotonic as time
8 try:
9 from _queue import SimpleQueue
10 except ImportError:
11 SimpleQueue = None
12
13 __all__ = ['Empty', 'Full', 'Queue', 'PriorityQueue', 'LifoQueue', 'SimpleQueue']
14
15
16 try:
17 from _queue import Empty
18 except ImportError:
19 class ESC[4;38;5;81mEmpty(ESC[4;38;5;149mException):
20 'Exception raised by Queue.get(block=0)/get_nowait().'
21 pass
22
23 class ESC[4;38;5;81mFull(ESC[4;38;5;149mException):
24 'Exception raised by Queue.put(block=0)/put_nowait().'
25 pass
26
27
28 class ESC[4;38;5;81mQueue:
29 '''Create a queue object with a given maximum size.
30
31 If maxsize is <= 0, the queue size is infinite.
32 '''
33
34 def __init__(self, maxsize=0):
35 self.maxsize = maxsize
36 self._init(maxsize)
37
38 # mutex must be held whenever the queue is mutating. All methods
39 # that acquire mutex must release it before returning. mutex
40 # is shared between the three conditions, so acquiring and
41 # releasing the conditions also acquires and releases mutex.
42 self.mutex = threading.Lock()
43
44 # Notify not_empty whenever an item is added to the queue; a
45 # thread waiting to get is notified then.
46 self.not_empty = threading.Condition(self.mutex)
47
48 # Notify not_full whenever an item is removed from the queue;
49 # a thread waiting to put is notified then.
50 self.not_full = threading.Condition(self.mutex)
51
52 # Notify all_tasks_done whenever the number of unfinished tasks
53 # drops to zero; thread waiting to join() is notified to resume
54 self.all_tasks_done = threading.Condition(self.mutex)
55 self.unfinished_tasks = 0
56
57 def task_done(self):
58 '''Indicate that a formerly enqueued task is complete.
59
60 Used by Queue consumer threads. For each get() used to fetch a task,
61 a subsequent call to task_done() tells the queue that the processing
62 on the task is complete.
63
64 If a join() is currently blocking, it will resume when all items
65 have been processed (meaning that a task_done() call was received
66 for every item that had been put() into the queue).
67
68 Raises a ValueError if called more times than there were items
69 placed in the queue.
70 '''
71 with self.all_tasks_done:
72 unfinished = self.unfinished_tasks - 1
73 if unfinished <= 0:
74 if unfinished < 0:
75 raise ValueError('task_done() called too many times')
76 self.all_tasks_done.notify_all()
77 self.unfinished_tasks = unfinished
78
79 def join(self):
80 '''Blocks until all items in the Queue have been gotten and processed.
81
82 The count of unfinished tasks goes up whenever an item is added to the
83 queue. The count goes down whenever a consumer thread calls task_done()
84 to indicate the item was retrieved and all work on it is complete.
85
86 When the count of unfinished tasks drops to zero, join() unblocks.
87 '''
88 with self.all_tasks_done:
89 while self.unfinished_tasks:
90 self.all_tasks_done.wait()
91
92 def qsize(self):
93 '''Return the approximate size of the queue (not reliable!).'''
94 with self.mutex:
95 return self._qsize()
96
97 def empty(self):
98 '''Return True if the queue is empty, False otherwise (not reliable!).
99
100 This method is likely to be removed at some point. Use qsize() == 0
101 as a direct substitute, but be aware that either approach risks a race
102 condition where a queue can grow before the result of empty() or
103 qsize() can be used.
104
105 To create code that needs to wait for all queued tasks to be
106 completed, the preferred technique is to use the join() method.
107 '''
108 with self.mutex:
109 return not self._qsize()
110
111 def full(self):
112 '''Return True if the queue is full, False otherwise (not reliable!).
113
114 This method is likely to be removed at some point. Use qsize() >= n
115 as a direct substitute, but be aware that either approach risks a race
116 condition where a queue can shrink before the result of full() or
117 qsize() can be used.
118 '''
119 with self.mutex:
120 return 0 < self.maxsize <= self._qsize()
121
122 def put(self, item, block=True, timeout=None):
123 '''Put an item into the queue.
124
125 If optional args 'block' is true and 'timeout' is None (the default),
126 block if necessary until a free slot is available. If 'timeout' is
127 a non-negative number, it blocks at most 'timeout' seconds and raises
128 the Full exception if no free slot was available within that time.
129 Otherwise ('block' is false), put an item on the queue if a free slot
130 is immediately available, else raise the Full exception ('timeout'
131 is ignored in that case).
132 '''
133 with self.not_full:
134 if self.maxsize > 0:
135 if not block:
136 if self._qsize() >= self.maxsize:
137 raise Full
138 elif timeout is None:
139 while self._qsize() >= self.maxsize:
140 self.not_full.wait()
141 elif timeout < 0:
142 raise ValueError("'timeout' must be a non-negative number")
143 else:
144 endtime = time() + timeout
145 while self._qsize() >= self.maxsize:
146 remaining = endtime - time()
147 if remaining <= 0.0:
148 raise Full
149 self.not_full.wait(remaining)
150 self._put(item)
151 self.unfinished_tasks += 1
152 self.not_empty.notify()
153
154 def get(self, block=True, timeout=None):
155 '''Remove and return an item from the queue.
156
157 If optional args 'block' is true and 'timeout' is None (the default),
158 block if necessary until an item is available. If 'timeout' is
159 a non-negative number, it blocks at most 'timeout' seconds and raises
160 the Empty exception if no item was available within that time.
161 Otherwise ('block' is false), return an item if one is immediately
162 available, else raise the Empty exception ('timeout' is ignored
163 in that case).
164 '''
165 with self.not_empty:
166 if not block:
167 if not self._qsize():
168 raise Empty
169 elif timeout is None:
170 while not self._qsize():
171 self.not_empty.wait()
172 elif timeout < 0:
173 raise ValueError("'timeout' must be a non-negative number")
174 else:
175 endtime = time() + timeout
176 while not self._qsize():
177 remaining = endtime - time()
178 if remaining <= 0.0:
179 raise Empty
180 self.not_empty.wait(remaining)
181 item = self._get()
182 self.not_full.notify()
183 return item
184
185 def put_nowait(self, item):
186 '''Put an item into the queue without blocking.
187
188 Only enqueue the item if a free slot is immediately available.
189 Otherwise raise the Full exception.
190 '''
191 return self.put(item, block=False)
192
193 def get_nowait(self):
194 '''Remove and return an item from the queue without blocking.
195
196 Only get an item if one is immediately available. Otherwise
197 raise the Empty exception.
198 '''
199 return self.get(block=False)
200
201 # Override these methods to implement other queue organizations
202 # (e.g. stack or priority queue).
203 # These will only be called with appropriate locks held
204
205 # Initialize the queue representation
206 def _init(self, maxsize):
207 self.queue = deque()
208
209 def _qsize(self):
210 return len(self.queue)
211
212 # Put a new item in the queue
213 def _put(self, item):
214 self.queue.append(item)
215
216 # Get an item from the queue
217 def _get(self):
218 return self.queue.popleft()
219
220 __class_getitem__ = classmethod(types.GenericAlias)
221
222
223 class ESC[4;38;5;81mPriorityQueue(ESC[4;38;5;149mQueue):
224 '''Variant of Queue that retrieves open entries in priority order (lowest first).
225
226 Entries are typically tuples of the form: (priority number, data).
227 '''
228
229 def _init(self, maxsize):
230 self.queue = []
231
232 def _qsize(self):
233 return len(self.queue)
234
235 def _put(self, item):
236 heappush(self.queue, item)
237
238 def _get(self):
239 return heappop(self.queue)
240
241
242 class ESC[4;38;5;81mLifoQueue(ESC[4;38;5;149mQueue):
243 '''Variant of Queue that retrieves most recently added entries first.'''
244
245 def _init(self, maxsize):
246 self.queue = []
247
248 def _qsize(self):
249 return len(self.queue)
250
251 def _put(self, item):
252 self.queue.append(item)
253
254 def _get(self):
255 return self.queue.pop()
256
257
258 class ESC[4;38;5;81m_PySimpleQueue:
259 '''Simple, unbounded FIFO queue.
260
261 This pure Python implementation is not reentrant.
262 '''
263 # Note: while this pure Python version provides fairness
264 # (by using a threading.Semaphore which is itself fair, being based
265 # on threading.Condition), fairness is not part of the API contract.
266 # This allows the C version to use a different implementation.
267
268 def __init__(self):
269 self._queue = deque()
270 self._count = threading.Semaphore(0)
271
272 def put(self, item, block=True, timeout=None):
273 '''Put the item on the queue.
274
275 The optional 'block' and 'timeout' arguments are ignored, as this method
276 never blocks. They are provided for compatibility with the Queue class.
277 '''
278 self._queue.append(item)
279 self._count.release()
280
281 def get(self, block=True, timeout=None):
282 '''Remove and return an item from the queue.
283
284 If optional args 'block' is true and 'timeout' is None (the default),
285 block if necessary until an item is available. If 'timeout' is
286 a non-negative number, it blocks at most 'timeout' seconds and raises
287 the Empty exception if no item was available within that time.
288 Otherwise ('block' is false), return an item if one is immediately
289 available, else raise the Empty exception ('timeout' is ignored
290 in that case).
291 '''
292 if timeout is not None and timeout < 0:
293 raise ValueError("'timeout' must be a non-negative number")
294 if not self._count.acquire(block, timeout):
295 raise Empty
296 return self._queue.popleft()
297
298 def put_nowait(self, item):
299 '''Put an item into the queue without blocking.
300
301 This is exactly equivalent to `put(item, block=False)` and is only provided
302 for compatibility with the Queue class.
303 '''
304 return self.put(item, block=False)
305
306 def get_nowait(self):
307 '''Remove and return an item from the queue without blocking.
308
309 Only get an item if one is immediately available. Otherwise
310 raise the Empty exception.
311 '''
312 return self.get(block=False)
313
314 def empty(self):
315 '''Return True if the queue is empty, False otherwise (not reliable!).'''
316 return len(self._queue) == 0
317
318 def qsize(self):
319 '''Return the approximate size of the queue (not reliable!).'''
320 return len(self._queue)
321
322 __class_getitem__ = classmethod(types.GenericAlias)
323
324
325 if SimpleQueue is None:
326 SimpleQueue = _PySimpleQueue