1class Queue:
2"""Create a queue object with a given maximum size.
3 4 If maxsize is <= 0, the queue size is infinite.
5""" 6def__init__(self, maxsize=0):
7 self.maxsize = maxsize
8 self._init(maxsize)
9# mutex must be held whenever the queue is mutating. All methods 10# that acquire mutex must release it before returning. mutex 11# is shared between the three conditions, so acquiring and 12# releasing the conditions also acquires and releases mutex. 13 self.mutex = _threading.Lock()
14# Notify not_empty whenever an item is added to the queue; a 15# thread waiting to get is notified then. 16 self.not_empty = _threading.Condition(self.mutex)
17# Notify not_full whenever an item is removed from the queue; 18# a thread waiting to put is notified then. 19 self.not_full = _threading.Condition(self.mutex)
20# Notify all_tasks_done whenever the number of unfinished tasks 21# drops to zero; thread waiting to join() is notified to resume 22 self.all_tasks_done = _threading.Condition(self.mutex)
23 self.unfinished_tasks = 0
24 25def task_done(self):
26"""Indicate that a formerly enqueued task is complete.
27 28 Used by Queue consumer threads. For each get() used to fetch a task,
29 a subsequent call to task_done() tells the queue that the processing
30 on the task is complete.
31 32 If a join() is currently blocking, it will resume when all items
33 have been processed (meaning that a task_done() call was received
34 for every item that had been put() into the queue).
35 36 Raises a ValueError if called more times than there were items
37 placed in the queue.
38""" 39 self.all_tasks_done.acquire()
40try:
41 unfinished = self.unfinished_tasks - 1
42if unfinished <= 0:
43if unfinished < 0:
44raise ValueError('task_done() called too many times')
45 self.all_tasks_done.notify_all()
46 self.unfinished_tasks = unfinished
47finally:
48 self.all_tasks_done.release()
49 50def join(self):
51"""Blocks until all items in the Queue have been gotten and processed.
52 53 The count of unfinished tasks goes up whenever an item is added to the
54 queue. The count goes down whenever a consumer thread calls task_done()
55 to indicate the item was retrieved and all work on it is complete.
56 57 When the count of unfinished tasks drops to zero, join() unblocks.
58""" 59 self.all_tasks_done.acquire()
60try:
61while self.unfinished_tasks:
62 self.all_tasks_done.wait()
63finally:
64 self.all_tasks_done.release()
65 66def qsize(self):
67"""Return the approximate size of the queue (not reliable!).""" 68 self.mutex.acquire()
69 n = self._qsize()
70 self.mutex.release()
71return n
72 73def empty(self):
74"""Return True if the queue is empty, False otherwise (not reliable!).""" 75 self.mutex.acquire()
76 n = not self._qsize()
77 self.mutex.release()
78return n
79 80def full(self):
81"""Return True if the queue is full, False otherwise (not reliable!).""" 82 self.mutex.acquire()
83 n = 0 < self.maxsize == self._qsize()
84 self.mutex.release()
85return n
86 87def put(self, item, block=True, timeout=None):
88"""Put an item into the queue.
89 90 If optional args 'block' is true and 'timeout' is None (the default),
91 block if necessary until a free slot is available. If 'timeout' is
92 a non-negative number, it blocks at most 'timeout' seconds and raises
93 the Full exception if no free slot was available within that time.
94 Otherwise ('block' is false), put an item on the queue if a free slot
95 is immediately available, else raise the Full exception ('timeout'
96 is ignored in that case).
97""" 98 self.not_full.acquire()
99try:
100if self.maxsize > 0:
101ifnot block:
102if self._qsize() == self.maxsize:
103raise Full
104elif timeout is None:
105while self._qsize() == self.maxsize:
106 self.not_full.wait()
107elif timeout < 0:
108raise ValueError("'timeout' must be a non-negative number")
109else:
110 endtime = _time() + timeout
111while self._qsize() == self.maxsize:
112 remaining = endtime - _time()
113if remaining <= 0.0:
114raise Full
115 self.not_full.wait(remaining)
116 self._put(item)
117 self.unfinished_tasks += 1
118 self.not_empty.notify()
119finally:
120 self.not_full.release()
121122def put_nowait(self, item):
123"""Put an item into the queue without blocking.
124125 Only enqueue the item if a free slot is immediately available.
126 Otherwise raise the Full exception.
127"""128return self.put(item, False)
129130def get(self, block=True, timeout=None):
131"""Remove and return an item from the queue.
132133 If optional args 'block' is true and 'timeout' is None (the default),
134 block if necessary until an item is available. If 'timeout' is
135 a non-negative number, it blocks at most 'timeout' seconds and raises
136 the Empty exception if no item was available within that time.
137 Otherwise ('block' is false), return an item if one is immediately
138 available, else raise the Empty exception ('timeout' is ignored
139 in that case).
140"""141 self.not_empty.acquire()
142try:
143ifnot block:
144ifnot self._qsize():
145raise Empty
146elif timeout is None:
147whilenot self._qsize():
148 self.not_empty.wait()
149elif timeout < 0:
150raise ValueError("'timeout' must be a non-negative number")
151else:
152 endtime = _time() + timeout
153whilenot self._qsize():
154 remaining = endtime - _time()
155if remaining <= 0.0:
156raise Empty
157 self.not_empty.wait(remaining)
158 item = self._get()
159 self.not_full.notify()
160return item
161finally:
162 self.not_empty.release()
163164def get_nowait(self):
165"""Remove and return an item from the queue without blocking.
166167 Only get an item if one is immediately available. Otherwise
168 raise the Empty exception.
169"""170return self.get(False)
171172# Override these methods to implement other queue organizations 173# (e.g. stack or priority queue). 174# These will only be called with appropriate locks held 175176# Initialize the queue representation 177def _init(self, maxsize):
178 self.queue = deque()
179180def _qsize(self, len=len):
181return len(self.queue)
182183# Put a new item in the queue 184def _put(self, item):
185 self.queue.append(item)
186187# Get an item from the queue 188def _get(self):
189return self.queue.popleft() View Code
