Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/queue.py: 33%
138 statements
« prev ^ index » next coverage.py v7.0.1, created at 2022-12-25 06:11 +0000
1'''A multi-producer, multi-consumer queue.'''
3import threading
4from collections import deque
5from heapq import heappush, heappop
6from time import monotonic as time
7try:
8 from _queue import SimpleQueue
9except ImportError:
10 SimpleQueue = None
12__all__ = ['Empty', 'Full', 'Queue', 'PriorityQueue', 'LifoQueue', 'SimpleQueue']
15try:
16 from _queue import Empty
17except ImportError:
18 class Empty(Exception):
19 'Exception raised by Queue.get(block=0)/get_nowait().'
20 pass
22class Full(Exception):
23 'Exception raised by Queue.put(block=0)/put_nowait().'
24 pass
27class Queue:
28 '''Create a queue object with a given maximum size.
30 If maxsize is <= 0, the queue size is infinite.
31 '''
33 def __init__(self, maxsize=0):
34 self.maxsize = maxsize
35 self._init(maxsize)
37 # mutex must be held whenever the queue is mutating. All methods
38 # that acquire mutex must release it before returning. mutex
39 # is shared between the three conditions, so acquiring and
40 # releasing the conditions also acquires and releases mutex.
41 self.mutex = threading.Lock()
43 # Notify not_empty whenever an item is added to the queue; a
44 # thread waiting to get is notified then.
45 self.not_empty = threading.Condition(self.mutex)
47 # Notify not_full whenever an item is removed from the queue;
48 # a thread waiting to put is notified then.
49 self.not_full = threading.Condition(self.mutex)
51 # Notify all_tasks_done whenever the number of unfinished tasks
52 # drops to zero; thread waiting to join() is notified to resume
53 self.all_tasks_done = threading.Condition(self.mutex)
54 self.unfinished_tasks = 0
56 def task_done(self):
57 '''Indicate that a formerly enqueued task is complete.
59 Used by Queue consumer threads. For each get() used to fetch a task,
60 a subsequent call to task_done() tells the queue that the processing
61 on the task is complete.
63 If a join() is currently blocking, it will resume when all items
64 have been processed (meaning that a task_done() call was received
65 for every item that had been put() into the queue).
67 Raises a ValueError if called more times than there were items
68 placed in the queue.
69 '''
70 with self.all_tasks_done:
71 unfinished = self.unfinished_tasks - 1
72 if unfinished <= 0:
73 if unfinished < 0:
74 raise ValueError('task_done() called too many times')
75 self.all_tasks_done.notify_all()
76 self.unfinished_tasks = unfinished
78 def join(self):
79 '''Blocks until all items in the Queue have been gotten and processed.
81 The count of unfinished tasks goes up whenever an item is added to the
82 queue. The count goes down whenever a consumer thread calls task_done()
83 to indicate the item was retrieved and all work on it is complete.
85 When the count of unfinished tasks drops to zero, join() unblocks.
86 '''
87 with self.all_tasks_done:
88 while self.unfinished_tasks:
89 self.all_tasks_done.wait()
91 def qsize(self):
92 '''Return the approximate size of the queue (not reliable!).'''
93 with self.mutex:
94 return self._qsize()
96 def empty(self):
97 '''Return True if the queue is empty, False otherwise (not reliable!).
99 This method is likely to be removed at some point. Use qsize() == 0
100 as a direct substitute, but be aware that either approach risks a race
101 condition where a queue can grow before the result of empty() or
102 qsize() can be used.
104 To create code that needs to wait for all queued tasks to be
105 completed, the preferred technique is to use the join() method.
106 '''
107 with self.mutex:
108 return not self._qsize()
110 def full(self):
111 '''Return True if the queue is full, False otherwise (not reliable!).
113 This method is likely to be removed at some point. Use qsize() >= n
114 as a direct substitute, but be aware that either approach risks a race
115 condition where a queue can shrink before the result of full() or
116 qsize() can be used.
117 '''
118 with self.mutex:
119 return 0 < self.maxsize <= self._qsize()
121 def put(self, item, block=True, timeout=None):
122 '''Put an item into the queue.
124 If optional args 'block' is true and 'timeout' is None (the default),
125 block if necessary until a free slot is available. If 'timeout' is
126 a non-negative number, it blocks at most 'timeout' seconds and raises
127 the Full exception if no free slot was available within that time.
128 Otherwise ('block' is false), put an item on the queue if a free slot
129 is immediately available, else raise the Full exception ('timeout'
130 is ignored in that case).
131 '''
132 with self.not_full:
133 if self.maxsize > 0:
134 if not block:
135 if self._qsize() >= self.maxsize:
136 raise Full
137 elif timeout is None:
138 while self._qsize() >= self.maxsize:
139 self.not_full.wait()
140 elif timeout < 0:
141 raise ValueError("'timeout' must be a non-negative number")
142 else:
143 endtime = time() + timeout
144 while self._qsize() >= self.maxsize:
145 remaining = endtime - time()
146 if remaining <= 0.0:
147 raise Full
148 self.not_full.wait(remaining)
149 self._put(item)
150 self.unfinished_tasks += 1
151 self.not_empty.notify()
153 def get(self, block=True, timeout=None):
154 '''Remove and return an item from the queue.
156 If optional args 'block' is true and 'timeout' is None (the default),
157 block if necessary until an item is available. If 'timeout' is
158 a non-negative number, it blocks at most 'timeout' seconds and raises
159 the Empty exception if no item was available within that time.
160 Otherwise ('block' is false), return an item if one is immediately
161 available, else raise the Empty exception ('timeout' is ignored
162 in that case).
163 '''
164 with self.not_empty:
165 if not block:
166 if not self._qsize():
167 raise Empty
168 elif timeout is None:
169 while not self._qsize():
170 self.not_empty.wait()
171 elif timeout < 0:
172 raise ValueError("'timeout' must be a non-negative number")
173 else:
174 endtime = time() + timeout
175 while not self._qsize():
176 remaining = endtime - time()
177 if remaining <= 0.0:
178 raise Empty
179 self.not_empty.wait(remaining)
180 item = self._get()
181 self.not_full.notify()
182 return item
184 def put_nowait(self, item):
185 '''Put an item into the queue without blocking.
187 Only enqueue the item if a free slot is immediately available.
188 Otherwise raise the Full exception.
189 '''
190 return self.put(item, block=False)
192 def get_nowait(self):
193 '''Remove and return an item from the queue without blocking.
195 Only get an item if one is immediately available. Otherwise
196 raise the Empty exception.
197 '''
198 return self.get(block=False)
200 # Override these methods to implement other queue organizations
201 # (e.g. stack or priority queue).
202 # These will only be called with appropriate locks held
204 # Initialize the queue representation
205 def _init(self, maxsize):
206 self.queue = deque()
208 def _qsize(self):
209 return len(self.queue)
211 # Put a new item in the queue
212 def _put(self, item):
213 self.queue.append(item)
215 # Get an item from the queue
216 def _get(self):
217 return self.queue.popleft()
220class PriorityQueue(Queue):
221 '''Variant of Queue that retrieves open entries in priority order (lowest first).
223 Entries are typically tuples of the form: (priority number, data).
224 '''
226 def _init(self, maxsize):
227 self.queue = []
229 def _qsize(self):
230 return len(self.queue)
232 def _put(self, item):
233 heappush(self.queue, item)
235 def _get(self):
236 return heappop(self.queue)
239class LifoQueue(Queue):
240 '''Variant of Queue that retrieves most recently added entries first.'''
242 def _init(self, maxsize):
243 self.queue = []
245 def _qsize(self):
246 return len(self.queue)
248 def _put(self, item):
249 self.queue.append(item)
251 def _get(self):
252 return self.queue.pop()
255class _PySimpleQueue:
256 '''Simple, unbounded FIFO queue.
258 This pure Python implementation is not reentrant.
259 '''
260 # Note: while this pure Python version provides fairness
261 # (by using a threading.Semaphore which is itself fair, being based
262 # on threading.Condition), fairness is not part of the API contract.
263 # This allows the C version to use a different implementation.
265 def __init__(self):
266 self._queue = deque()
267 self._count = threading.Semaphore(0)
269 def put(self, item, block=True, timeout=None):
270 '''Put the item on the queue.
272 The optional 'block' and 'timeout' arguments are ignored, as this method
273 never blocks. They are provided for compatibility with the Queue class.
274 '''
275 self._queue.append(item)
276 self._count.release()
278 def get(self, block=True, timeout=None):
279 '''Remove and return an item from the queue.
281 If optional args 'block' is true and 'timeout' is None (the default),
282 block if necessary until an item is available. If 'timeout' is
283 a non-negative number, it blocks at most 'timeout' seconds and raises
284 the Empty exception if no item was available within that time.
285 Otherwise ('block' is false), return an item if one is immediately
286 available, else raise the Empty exception ('timeout' is ignored
287 in that case).
288 '''
289 if timeout is not None and timeout < 0:
290 raise ValueError("'timeout' must be a non-negative number")
291 if not self._count.acquire(block, timeout):
292 raise Empty
293 return self._queue.popleft()
295 def put_nowait(self, item):
296 '''Put an item into the queue without blocking.
298 This is exactly equivalent to `put(item)` and is only provided
299 for compatibility with the Queue class.
300 '''
301 return self.put(item, block=False)
303 def get_nowait(self):
304 '''Remove and return an item from the queue without blocking.
306 Only get an item if one is immediately available. Otherwise
307 raise the Empty exception.
308 '''
309 return self.get(block=False)
311 def empty(self):
312 '''Return True if the queue is empty, False otherwise (not reliable!).'''
313 return len(self._queue) == 0
315 def qsize(self):
316 '''Return the approximate size of the queue (not reliable!).'''
317 return len(self._queue)
320if SimpleQueue is None:
321 SimpleQueue = _PySimpleQueue