1 """A multi-producer, multi-consumer queue."""

     2 

     3 from time import time as _time

     4 from collections import deque

     5 import heapq

     6 

     7 __all__ = ['Empty', 'Full', 'Queue', 'PriorityQueue', 'LifoQueue']

     8 

     9 class Empty(Exception):

    10     "Exception raised by Queue.get(block=0)/get_nowait()."

    11     pass

    12 

    13 class Full(Exception):

    14     "Exception raised by Queue.put(block=0)/put_nowait()."

    15     pass

    16 

    17 class Queue:

    18     """Create a queue object with a given maximum size.

    19 

    20     If maxsize is <= 0, the queue size is infinite.

    21     """

    22     def __init__(self, maxsize=0):

    23         try:

    24             import threading

    25         except ImportError:

    26             import dummy_threading as threading

    27         self.maxsize = maxsize

    28         self._init(maxsize)

    29         # mutex must be held whenever the queue is mutating.  All methods

    30         # that acquire mutex must release it before returning.  mutex

    31         # is shared between the three conditions, so acquiring and

    32         # releasing the conditions also acquires and releases mutex.

    33         self.mutex = threading.Lock()

    34         # Notify not_empty whenever an item is added to the queue; a

    35         # thread waiting to get is notified then.

    36         self.not_empty = threading.Condition(self.mutex)

    37         # Notify not_full whenever an item is removed from the queue;

    38         # a thread waiting to put is notified then.

    39         self.not_full = threading.Condition(self.mutex)

    40         # Notify all_tasks_done whenever the number of unfinished tasks

    41         # drops to zero; thread waiting to join() is notified to resume

    42         self.all_tasks_done = threading.Condition(self.mutex)

    43         self.unfinished_tasks = 0

    44 

    45     def task_done(self):

    46         """Indicate that a formerly enqueued task is complete.

    47 

    48         Used by Queue consumer threads.  For each get() used to fetch a task,

    49         a subsequent call to task_done() tells the queue that the processing

    50         on the task is complete.

    51 

    52         If a join() is currently blocking, it will resume when all items

    53         have been processed (meaning that a task_done() call was received

    54         for every item that had been put() into the queue).

    55 

    56         Raises a ValueError if called more times than there were items

    57         placed in the queue.

    58         """

    59         self.all_tasks_done.acquire()

    60         try:

    61             unfinished = self.unfinished_tasks - 1

    62             if unfinished <= 0:

    63                 if unfinished < 0:

    64                     raise ValueError('task_done() called too many times')

    65                 self.all_tasks_done.notify_all()

    66             self.unfinished_tasks = unfinished

    67         finally:

    68             self.all_tasks_done.release()

    69 

    70     def join(self):

    71         """Blocks until all items in the Queue have been gotten and processed.

    72 

    73         The count of unfinished tasks goes up whenever an item is added to the

    74         queue. The count goes down whenever a consumer thread calls task_done()

    75         to indicate the item was retrieved and all work on it is complete.

    76 

    77         When the count of unfinished tasks drops to zero, join() unblocks.

    78         """

    79         self.all_tasks_done.acquire()

    80         try:

    81             while self.unfinished_tasks:

    82                 self.all_tasks_done.wait()

    83         finally:

    84             self.all_tasks_done.release()

    85 

    86     def qsize(self):

    87         """Return the approximate size of the queue (not reliable!)."""

    88         self.mutex.acquire()

    89         n = self._qsize()

    90         self.mutex.release()

    91         return n

    92 

    93     def empty(self):

    94         """Return True if the queue is empty, False otherwise (not reliable!)."""

    95         self.mutex.acquire()

    96         n = not self._qsize()

    97         self.mutex.release()

    98         return n

    99 

   100     def full(self):

   101         """Return True if the queue is full, False otherwise (not reliable!)."""

   102         self.mutex.acquire()

   103         n = 0 < self.maxsize == self._qsize()

   104         self.mutex.release()

   105         return n

   106 

   107     def put(self, item, block=True, timeout=None):

   108         """Put an item into the queue.

   109 

   110         If optional args 'block' is true and 'timeout' is None (the default),

   111         block if necessary until a free slot is available. If 'timeout' is

   112         a positive number, it blocks at most 'timeout' seconds and raises

   113         the Full exception if no free slot was available within that time.

   114         Otherwise ('block' is false), put an item on the queue if a free slot

   115         is immediately available, else raise the Full exception ('timeout'

   116         is ignored in that case).

   117         """

   118         self.not_full.acquire()

   119         try:

   120             if self.maxsize > 0:

   121                 if not block:

   122                     if self._qsize() == self.maxsize:

   123                         raise Full

   124                 elif timeout is None:

   125                     while self._qsize() == self.maxsize:

   126                         self.not_full.wait()

   127                 elif timeout < 0:

   128                     raise ValueError("'timeout' must be a positive number")

   129                 else:

   130                     endtime = _time() + timeout

   131                     while self._qsize() == self.maxsize:

   132                         remaining = endtime - _time()

   133                         if remaining <= 0.0:

   134                             raise Full

   135                         self.not_full.wait(remaining)

   136             self._put(item)

   137             self.unfinished_tasks += 1

   138             self.not_empty.notify()

   139         finally:

   140             self.not_full.release()

   141 

   142     def put_nowait(self, item):

   143         """Put an item into the queue without blocking.

   144 

   145         Only enqueue the item if a free slot is immediately available.

   146         Otherwise raise the Full exception.

   147         """

   148         return self.put(item, False)

   149 

   150     def get(self, block=True, timeout=None):

   151         """Remove and return an item from the queue.

   152 

   153         If optional args 'block' is true and 'timeout' is None (the default),

   154         block if necessary until an item is available. If 'timeout' is

   155         a positive number, it blocks at most 'timeout' seconds and raises

   156         the Empty exception if no item was available within that time.

   157         Otherwise ('block' is false), return an item if one is immediately

   158         available, else raise the Empty exception ('timeout' is ignored

   159         in that case).

   160         """

   161         self.not_empty.acquire()

   162         try:

   163             if not block:

   164                 if not self._qsize():

   165                     raise Empty

   166             elif timeout is None:

   167                 while not self._qsize():

   168                     self.not_empty.wait()

   169             elif timeout < 0:

   170                 raise ValueError("'timeout' must be a positive number")

   171             else:

   172                 endtime = _time() + timeout

   173                 while not self._qsize():

   174                     remaining = endtime - _time()

   175                     if remaining <= 0.0:

   176                         raise Empty

   177                     self.not_empty.wait(remaining)

   178             item = self._get()

   179             self.not_full.notify()

   180             return item

   181         finally:

   182             self.not_empty.release()

   183 

   184     def get_nowait(self):

   185         """Remove and return an item from the queue without blocking.

   186 

   187         Only get an item if one is immediately available. Otherwise

   188         raise the Empty exception.

   189         """

   190         return self.get(False)

   191 

   192     # Override these methods to implement other queue organizations

   193     # (e.g. stack or priority queue).

   194     # These will only be called with appropriate locks held

   195 

   196     # Initialize the queue representation

   197     def _init(self, maxsize):

   198         self.queue = deque()

   199 

   200     def _qsize(self, len=len):

   201         return len(self.queue)

   202 

   203     # Put a new item in the queue

   204     def _put(self, item):

   205         self.queue.append(item)

   206 

   207     # Get an item from the queue

   208     def _get(self):

   209         return self.queue.popleft()

   210 

   211 

   212 class PriorityQueue(Queue):

   213     '''Variant of Queue that retrieves open entries in priority order (lowest first).

   214 

   215     Entries are typically tuples of the form:  (priority number, data).

   216     '''

   217 

   218     def _init(self, maxsize):

   219         self.queue = []

   220 

   221     def _qsize(self, len=len):

   222         return len(self.queue)

   223 

   224     def _put(self, item, heappush=heapq.heappush):

   225         heappush(self.queue, item)

   226 

   227     def _get(self, heappop=heapq.heappop):

   228         return heappop(self.queue)

   229 

   230 

   231 class LifoQueue(Queue):

   232     '''Variant of Queue that retrieves most recently added entries first.'''

   233 

   234     def _init(self, maxsize):

   235         self.queue = []

   236 

   237     def _qsize(self, len=len):

   238         return len(self.queue)

   239 

   240     def _put(self, item):

   241         self.queue.append(item)

   242 

   243     def _get(self):

   244         return self.queue.pop()