1__all__ = ('Queue', 'PriorityQueue', 'LifoQueue', 'QueueFull', 'QueueEmpty')
2
3import collections
4import heapq
5import warnings
6
7from . import events
8from . import locks
9
10
11class QueueEmpty(Exception):
12    """Raised when Queue.get_nowait() is called on an empty Queue."""
13    pass
14
15
16class QueueFull(Exception):
17    """Raised when the Queue.put_nowait() method is called on a full Queue."""
18    pass
19
20
21class 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 "await 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
29    with qsize(), since your single-threaded asyncio application won't be
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            warnings.warn("The loop argument is deprecated since Python 3.8, "
39                          "and scheduled for removal in Python 3.10.",
40                          DeprecationWarning, stacklevel=2)
41        self._maxsize = maxsize
42
43        # Futures.
44        self._getters = collections.deque()
45        # Futures.
46        self._putters = collections.deque()
47        self._unfinished_tasks = 0
48        self._finished = locks.Event(loop=loop)
49        self._finished.set()
50        self._init(maxsize)
51
52    # These three are overridable in subclasses.
53
54    def _init(self, maxsize):
55        self._queue = collections.deque()
56
57    def _get(self):
58        return self._queue.popleft()
59
60    def _put(self, item):
61        self._queue.append(item)
62
63    # End of the overridable methods.
64
65    def _wakeup_next(self, waiters):
66        # Wake up the next waiter (if any) that isn't cancelled.
67        while waiters:
68            waiter = waiters.popleft()
69            if not waiter.done():
70                waiter.set_result(None)
71                break
72
73    def __repr__(self):
74        return f'<{type(self).__name__} at {id(self):#x} {self._format()}>'
75
76    def __str__(self):
77        return f'<{type(self).__name__} {self._format()}>'
78
79    def _format(self):
80        result = f'maxsize={self._maxsize!r}'
81        if getattr(self, '_queue', None):
82            result += f' _queue={list(self._queue)!r}'
83        if self._getters:
84            result += f' _getters[{len(self._getters)}]'
85        if self._putters:
86            result += f' _putters[{len(self._putters)}]'
87        if self._unfinished_tasks:
88            result += f' tasks={self._unfinished_tasks}'
89        return result
90
91    def qsize(self):
92        """Number of items in the queue."""
93        return len(self._queue)
94
95    @property
96    def maxsize(self):
97        """Number of items allowed in the queue."""
98        return self._maxsize
99
100    def empty(self):
101        """Return True if the queue is empty, False otherwise."""
102        return not self._queue
103
104    def full(self):
105        """Return True if there are maxsize items in the queue.
106
107        Note: if the Queue was initialized with maxsize=0 (the default),
108        then full() is never True.
109        """
110        if self._maxsize <= 0:
111            return False
112        else:
113            return self.qsize() >= self._maxsize
114
115    async def put(self, item):
116        """Put an item into the queue.
117
118        Put an item into the queue. If the queue is full, wait until a free
119        slot is available before adding item.
120        """
121        while self.full():
122            putter = self._loop.create_future()
123            self._putters.append(putter)
124            try:
125                await putter
126            except:
127                putter.cancel()  # Just in case putter is not done yet.
128                try:
129                    # Clean self._putters from canceled putters.
130                    self._putters.remove(putter)
131                except ValueError:
132                    # The putter could be removed from self._putters by a
133                    # previous get_nowait call.
134                    pass
135                if not self.full() and not putter.cancelled():
136                    # We were woken up by get_nowait(), but can't take
137                    # the call.  Wake up the next in line.
138                    self._wakeup_next(self._putters)
139                raise
140        return self.put_nowait(item)
141
142    def put_nowait(self, item):
143        """Put an item into the queue without blocking.
144
145        If no free slot is immediately available, raise QueueFull.
146        """
147        if self.full():
148            raise QueueFull
149        self._put(item)
150        self._unfinished_tasks += 1
151        self._finished.clear()
152        self._wakeup_next(self._getters)
153
154    async def get(self):
155        """Remove and return an item from the queue.
156
157        If queue is empty, wait until an item is available.
158        """
159        while self.empty():
160            getter = self._loop.create_future()
161            self._getters.append(getter)
162            try:
163                await getter
164            except:
165                getter.cancel()  # Just in case getter is not done yet.
166                try:
167                    # Clean self._getters from canceled getters.
168                    self._getters.remove(getter)
169                except ValueError:
170                    # The getter could be removed from self._getters by a
171                    # previous put_nowait call.
172                    pass
173                if not self.empty() and not getter.cancelled():
174                    # We were woken up by put_nowait(), but can't take
175                    # the call.  Wake up the next in line.
176                    self._wakeup_next(self._getters)
177                raise
178        return self.get_nowait()
179
180    def get_nowait(self):
181        """Remove and return an item from the queue.
182
183        Return an item if one is immediately available, else raise QueueEmpty.
184        """
185        if self.empty():
186            raise QueueEmpty
187        item = self._get()
188        self._wakeup_next(self._putters)
189        return item
190
191    def task_done(self):
192        """Indicate that a formerly enqueued task is complete.
193
194        Used by queue consumers. For each get() used to fetch a task,
195        a subsequent call to task_done() tells the queue that the processing
196        on the task is complete.
197
198        If a join() is currently blocking, it will resume when all items have
199        been processed (meaning that a task_done() call was received for every
200        item that had been put() into the queue).
201
202        Raises ValueError if called more times than there were items placed in
203        the queue.
204        """
205        if self._unfinished_tasks <= 0:
206            raise ValueError('task_done() called too many times')
207        self._unfinished_tasks -= 1
208        if self._unfinished_tasks == 0:
209            self._finished.set()
210
211    async def join(self):
212        """Block until all items in the queue have been gotten and processed.
213
214        The count of unfinished tasks goes up whenever an item is added to the
215        queue. The count goes down whenever a consumer calls task_done() to
216        indicate that the item was retrieved and all work on it is complete.
217        When the count of unfinished tasks drops to zero, join() unblocks.
218        """
219        if self._unfinished_tasks > 0:
220            await self._finished.wait()
221
222
223class PriorityQueue(Queue):
224    """A subclass of Queue; retrieves 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 _put(self, item, heappush=heapq.heappush):
233        heappush(self._queue, item)
234
235    def _get(self, heappop=heapq.heappop):
236        return heappop(self._queue)
237
238
239class LifoQueue(Queue):
240    """A subclass of Queue that retrieves most recently added entries first."""
241
242    def _init(self, maxsize):
243        self._queue = []
244
245    def _put(self, item):
246        self._queue.append(item)
247
248    def _get(self):
249        return self._queue.pop()
250