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 A typical pattern forĮntries is a tuple in the form: (priority_number, data). One that would be returned by min(entries)). 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. Once Enqued its has to be dequeued for making it available to others.The queue module implements multi-producer, multi-consumer queues. Its for exclsuive locking of resource.This comes in secnarios where multiple browse/update operation is required for the same file TSQ,TDQ etc. But I try the same statement enqueue resource(XXAA) statement and the response is normal, any one can explain this for me ? I have read some manuals already but I still do not know in what situation we need to use the enqueue/dequeue statement.Īnother question, when I testing a program, it always come to "queue busy" when the enqueue resource(XXAA) statement is executed. What situation we need to use the enqueue/dequeue statement What situation we need to use the enqueue/dequeue statement -IBM Mainframes
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