1'''A multi-producer, multi-consumer queue.''' 2 3import threading 4import types 5from collections import deque 6from heapq import heappush, heappop 7from time import monotonic as time 8try: 9 from _queue import SimpleQueue 10except ImportError: 11 SimpleQueue = None 12 13__all__ = ['Empty', 'Full', 'Queue', 'PriorityQueue', 'LifoQueue', 'SimpleQueue'] 14 15 16try: 17 from _queue import Empty 18except ImportError: 19 class Empty(Exception): 20 'Exception raised by Queue.get(block=0)/get_nowait().' 21 pass 22 23class Full(Exception): 24 'Exception raised by Queue.put(block=0)/put_nowait().' 25 pass 26 27 28class Queue: 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 223class PriorityQueue(Queue): 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 242class LifoQueue(Queue): 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 258class _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)` 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 325if SimpleQueue is None: 326 SimpleQueue = _PySimpleQueue 327