Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 1 | """Queues""" |
| 2 | |
| 3 | __all__ = ['Queue', 'PriorityQueue', 'LifoQueue', 'JoinableQueue', |
| 4 | 'Full', 'Empty'] |
| 5 | |
| 6 | import collections |
| 7 | import heapq |
| 8 | import queue |
| 9 | |
| 10 | from . import events |
| 11 | from . import futures |
| 12 | from . import locks |
| 13 | from .tasks import coroutine |
| 14 | |
| 15 | |
| 16 | # Re-export queue.Full and .Empty exceptions. |
| 17 | Full = queue.Full |
| 18 | Empty = queue.Empty |
| 19 | |
| 20 | |
| 21 | class Queue: |
| 22 | """A queue, useful for coordinating producer and consumer coroutines. |
| 23 | |
| 24 | If maxsize is less than or equal to zero, the queue size is infinite. If it |
| 25 | is an integer greater than 0, then "yield from put()" will block when the |
| 26 | queue reaches maxsize, until an item is removed by get(). |
| 27 | |
| 28 | Unlike the standard library Queue, you can reliably know this Queue's size |
Victor Stinner | 2748bc7 | 2013-12-13 10:57:04 +0100 | [diff] [blame] | 29 | with qsize(), since your single-threaded asyncio application won't be |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 30 | interrupted between calling qsize() and doing an operation on the Queue. |
| 31 | """ |
| 32 | |
| 33 | def __init__(self, maxsize=0, *, loop=None): |
| 34 | if loop is None: |
| 35 | self._loop = events.get_event_loop() |
| 36 | else: |
| 37 | self._loop = loop |
| 38 | self._maxsize = maxsize |
| 39 | |
| 40 | # Futures. |
| 41 | self._getters = collections.deque() |
| 42 | # Pairs of (item, Future). |
| 43 | self._putters = collections.deque() |
| 44 | self._init(maxsize) |
| 45 | |
| 46 | def _init(self, maxsize): |
| 47 | self._queue = collections.deque() |
| 48 | |
| 49 | def _get(self): |
| 50 | return self._queue.popleft() |
| 51 | |
| 52 | def _put(self, item): |
| 53 | self._queue.append(item) |
| 54 | |
| 55 | def __repr__(self): |
| 56 | return '<{} at {:#x} {}>'.format( |
| 57 | type(self).__name__, id(self), self._format()) |
| 58 | |
| 59 | def __str__(self): |
| 60 | return '<{} {}>'.format(type(self).__name__, self._format()) |
| 61 | |
| 62 | def _format(self): |
| 63 | result = 'maxsize={!r}'.format(self._maxsize) |
| 64 | if getattr(self, '_queue', None): |
| 65 | result += ' _queue={!r}'.format(list(self._queue)) |
| 66 | if self._getters: |
| 67 | result += ' _getters[{}]'.format(len(self._getters)) |
| 68 | if self._putters: |
| 69 | result += ' _putters[{}]'.format(len(self._putters)) |
| 70 | return result |
| 71 | |
| 72 | def _consume_done_getters(self): |
| 73 | # Delete waiters at the head of the get() queue who've timed out. |
| 74 | while self._getters and self._getters[0].done(): |
| 75 | self._getters.popleft() |
| 76 | |
| 77 | def _consume_done_putters(self): |
| 78 | # Delete waiters at the head of the put() queue who've timed out. |
| 79 | while self._putters and self._putters[0][1].done(): |
| 80 | self._putters.popleft() |
| 81 | |
| 82 | def qsize(self): |
| 83 | """Number of items in the queue.""" |
| 84 | return len(self._queue) |
| 85 | |
| 86 | @property |
| 87 | def maxsize(self): |
| 88 | """Number of items allowed in the queue.""" |
| 89 | return self._maxsize |
| 90 | |
| 91 | def empty(self): |
| 92 | """Return True if the queue is empty, False otherwise.""" |
| 93 | return not self._queue |
| 94 | |
| 95 | def full(self): |
| 96 | """Return True if there are maxsize items in the queue. |
| 97 | |
| 98 | Note: if the Queue was initialized with maxsize=0 (the default), |
| 99 | then full() is never True. |
| 100 | """ |
| 101 | if self._maxsize <= 0: |
| 102 | return False |
| 103 | else: |
| 104 | return self.qsize() == self._maxsize |
| 105 | |
| 106 | @coroutine |
| 107 | def put(self, item): |
| 108 | """Put an item into the queue. |
| 109 | |
| 110 | If you yield from put(), wait until a free slot is available |
| 111 | before adding item. |
| 112 | """ |
| 113 | self._consume_done_getters() |
| 114 | if self._getters: |
| 115 | assert not self._queue, ( |
| 116 | 'queue non-empty, why are getters waiting?') |
| 117 | |
| 118 | getter = self._getters.popleft() |
| 119 | |
| 120 | # Use _put and _get instead of passing item straight to getter, in |
| 121 | # case a subclass has logic that must run (e.g. JoinableQueue). |
| 122 | self._put(item) |
| 123 | getter.set_result(self._get()) |
| 124 | |
| 125 | elif self._maxsize > 0 and self._maxsize == self.qsize(): |
| 126 | waiter = futures.Future(loop=self._loop) |
| 127 | |
| 128 | self._putters.append((item, waiter)) |
| 129 | yield from waiter |
| 130 | |
| 131 | else: |
| 132 | self._put(item) |
| 133 | |
| 134 | def put_nowait(self, item): |
| 135 | """Put an item into the queue without blocking. |
| 136 | |
| 137 | If no free slot is immediately available, raise Full. |
| 138 | """ |
| 139 | self._consume_done_getters() |
| 140 | if self._getters: |
| 141 | assert not self._queue, ( |
| 142 | 'queue non-empty, why are getters waiting?') |
| 143 | |
| 144 | getter = self._getters.popleft() |
| 145 | |
| 146 | # Use _put and _get instead of passing item straight to getter, in |
| 147 | # case a subclass has logic that must run (e.g. JoinableQueue). |
| 148 | self._put(item) |
| 149 | getter.set_result(self._get()) |
| 150 | |
| 151 | elif self._maxsize > 0 and self._maxsize == self.qsize(): |
| 152 | raise Full |
| 153 | else: |
| 154 | self._put(item) |
| 155 | |
| 156 | @coroutine |
| 157 | def get(self): |
| 158 | """Remove and return an item from the queue. |
| 159 | |
| 160 | If you yield from get(), wait until a item is available. |
| 161 | """ |
| 162 | self._consume_done_putters() |
| 163 | if self._putters: |
| 164 | assert self.full(), 'queue not full, why are putters waiting?' |
| 165 | item, putter = self._putters.popleft() |
| 166 | self._put(item) |
| 167 | |
| 168 | # When a getter runs and frees up a slot so this putter can |
| 169 | # run, we need to defer the put for a tick to ensure that |
| 170 | # getters and putters alternate perfectly. See |
| 171 | # ChannelTest.test_wait. |
| 172 | self._loop.call_soon(putter.set_result, None) |
| 173 | |
| 174 | return self._get() |
| 175 | |
| 176 | elif self.qsize(): |
| 177 | return self._get() |
| 178 | else: |
| 179 | waiter = futures.Future(loop=self._loop) |
| 180 | |
| 181 | self._getters.append(waiter) |
| 182 | return (yield from waiter) |
| 183 | |
| 184 | def get_nowait(self): |
| 185 | """Remove and return an item from the queue. |
| 186 | |
Guido van Rossum | 16c4239 | 2013-11-24 22:41:35 -0800 | [diff] [blame] | 187 | Return an item if one is immediately available, else raise Empty. |
Guido van Rossum | 27b7c7e | 2013-10-17 13:40:50 -0700 | [diff] [blame] | 188 | """ |
| 189 | self._consume_done_putters() |
| 190 | if self._putters: |
| 191 | assert self.full(), 'queue not full, why are putters waiting?' |
| 192 | item, putter = self._putters.popleft() |
| 193 | self._put(item) |
| 194 | # Wake putter on next tick. |
| 195 | putter.set_result(None) |
| 196 | |
| 197 | return self._get() |
| 198 | |
| 199 | elif self.qsize(): |
| 200 | return self._get() |
| 201 | else: |
| 202 | raise Empty |
| 203 | |
| 204 | |
| 205 | class PriorityQueue(Queue): |
| 206 | """A subclass of Queue; retrieves entries in priority order (lowest first). |
| 207 | |
| 208 | Entries are typically tuples of the form: (priority number, data). |
| 209 | """ |
| 210 | |
| 211 | def _init(self, maxsize): |
| 212 | self._queue = [] |
| 213 | |
| 214 | def _put(self, item, heappush=heapq.heappush): |
| 215 | heappush(self._queue, item) |
| 216 | |
| 217 | def _get(self, heappop=heapq.heappop): |
| 218 | return heappop(self._queue) |
| 219 | |
| 220 | |
| 221 | class LifoQueue(Queue): |
| 222 | """A subclass of Queue that retrieves most recently added entries first.""" |
| 223 | |
| 224 | def _init(self, maxsize): |
| 225 | self._queue = [] |
| 226 | |
| 227 | def _put(self, item): |
| 228 | self._queue.append(item) |
| 229 | |
| 230 | def _get(self): |
| 231 | return self._queue.pop() |
| 232 | |
| 233 | |
| 234 | class JoinableQueue(Queue): |
| 235 | """A subclass of Queue with task_done() and join() methods.""" |
| 236 | |
| 237 | def __init__(self, maxsize=0, *, loop=None): |
| 238 | super().__init__(maxsize=maxsize, loop=loop) |
| 239 | self._unfinished_tasks = 0 |
| 240 | self._finished = locks.Event(loop=self._loop) |
| 241 | self._finished.set() |
| 242 | |
| 243 | def _format(self): |
| 244 | result = Queue._format(self) |
| 245 | if self._unfinished_tasks: |
| 246 | result += ' tasks={}'.format(self._unfinished_tasks) |
| 247 | return result |
| 248 | |
| 249 | def _put(self, item): |
| 250 | super()._put(item) |
| 251 | self._unfinished_tasks += 1 |
| 252 | self._finished.clear() |
| 253 | |
| 254 | def task_done(self): |
| 255 | """Indicate that a formerly enqueued task is complete. |
| 256 | |
| 257 | Used by queue consumers. For each get() used to fetch a task, |
| 258 | a subsequent call to task_done() tells the queue that the processing |
| 259 | on the task is complete. |
| 260 | |
| 261 | If a join() is currently blocking, it will resume when all items have |
| 262 | been processed (meaning that a task_done() call was received for every |
| 263 | item that had been put() into the queue). |
| 264 | |
| 265 | Raises ValueError if called more times than there were items placed in |
| 266 | the queue. |
| 267 | """ |
| 268 | if self._unfinished_tasks <= 0: |
| 269 | raise ValueError('task_done() called too many times') |
| 270 | self._unfinished_tasks -= 1 |
| 271 | if self._unfinished_tasks == 0: |
| 272 | self._finished.set() |
| 273 | |
| 274 | @coroutine |
| 275 | def join(self): |
| 276 | """Block until all items in the queue have been gotten and processed. |
| 277 | |
| 278 | The count of unfinished tasks goes up whenever an item is added to the |
| 279 | queue. The count goes down whenever a consumer thread calls task_done() |
| 280 | to indicate that the item was retrieved and all work on it is complete. |
| 281 | When the count of unfinished tasks drops to zero, join() unblocks. |
| 282 | """ |
| 283 | if self._unfinished_tasks > 0: |
| 284 | yield from self._finished.wait() |