This means that no exceptionsĬan occur, and in particular a SIGINT will not trigger a KeyboardInterrupt. Prior to 3.0 on POSIX systems, and for all versions on Windows, ifīlock is true and timeout is None, this operation goes intoĪn uninterruptible wait on an underlying lock. Otherwise ( block is false), return an item if one is immediately available,Įlse raise the Empty exception ( timeout is ignored in that case). Raises the Empty exception if no item was available within that time. If timeout is a positive number, it blocks at most timeout seconds and Timeout is None (the default), block if necessary until an item is available. Remove and return an item from the queue. put_nowait ( item ) ¶Įquivalent to put(item, block=False). Immediately available, else raise the Full exception ( timeout is Otherwise ( block is false), put an item on the queue if a free slot is The Full exception if no free slot was available within that time. Timeout is a positive number, it blocks at most timeout seconds and raises None (the default), block if necessary until a free slot is available. If optional args block is true and timeout is put ( item, block = True, timeout = None ) ¶ Guarantee that a subsequent call to put() will not block. Similarly, if full() returns False it doesn’t Returns True it doesn’t guarantee that a subsequent call to get() Return True if the queue is full, False otherwise. Guarantee that a subsequent call to get() will not block. Similarly, if empty() returns False it doesn’t Returns True it doesn’t guarantee that a subsequent call to put() Return True if the queue is empty, False otherwise. Guarantee that a subsequent get() will not block, nor will qsize() < maxsize Return the approximate size of the queue. Provide the public methods described below. Queue objects ( Queue, LifoQueue, or PriorityQueue) Full ¶Įxception raised when non-blocking put() (or Empty ¶Įxception raised when non-blocking get() (or That ignores the data item and only compares the priority number: If the data elements are not comparable, the data can be wrapped in a class Is a tuple in the form: (priority_number, data). The lowest valued entries are retrieved first (the lowest valued entry is the Maxsize is less than or equal to zero, the queue size is infinite. maxsize is an integer that sets the upperbound PriorityQueue ( maxsize = 0 ) ¶Ĭonstructor for a priority queue. Insertion willīlock once this size has been reached, until queue items are consumed. Limit on the number of items that can be placed in the queue. The queue module defines the following classes and exceptions: class queue. In exchange for the smaller functionality. Specific implementation provides additional guarantees In addition, the module implements a “simple” Internally, those three types of queues use locks to temporarily blockĬompeting threads however, they are not designed to handle reentrancy The entries are kept sorted (using the heapq module) and the The first retrieved (operating like a stack). LIFO queue, the most recently added entry is Queue, the first tasks added are the first retrieved. The module implements three types of queue, which differ only in the order in Module implements all the required locking semantics. It is especially useful in threaded programming when information must beĮxchanged safely between multiple threads. Numerical results show that the approximation is accurate even when the coefficient of variation of the service time and the number of channels of the system are as large as 20 and 200, respectively.The queue module implements multi-producer, multi-consumer queues. We found that certain properties of n p allow an estimation of the mean queue length of a large M/G/c queueing system through the approximate analysis of the mean queue length of a much smaller M/G/c queueing system. If the number of customers in the system is larger than n p, assumption 2 is used otherwise assumption 1 is used. The application of these two assumptions is coupled through the introduction of a parameter n p. The approximation method is developed based on the following assumptions: the residual service time of one busy server is independent of those of the other busy servers, and the system in which all the servers are busy is treated in the same way as a single-server system with c times the service rate of one of the servers. A relatively robust method for the approximate analysis of the mean queue length of an M/G/c queueing system is proposed.
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