# Push a dummy element causing a single thread to wake-up and stop. The last part of the controller code would need to be modified as follows: # Notify threads it's time to exit Note that the tutorial's original code would check exitFlag periodically every 1 second, whereas this modified queue requires you to push a dummy object into the queue after setting exitFlag to True - otherwise, the flag will never be checked. The queue's internal locking will ensure that two threads do not interfere for the duration of the call to get(), and no queueLock is needed. Print("%s processing %s" % (threadName, data)) Instead of checking empty() first, just rely directly on the blocking behavior of get(): def process_data(threadName, q): Let me show you how to use the threadsafe queue properly. Without this lock, two threads could enter into the if-statement and both issue a call to get(), meaning that one of them could block, waiting for an item that will never be pushed. The tutorial probably uses the lock to ensure that the thread has exclusive access to the queue from the call to empty() until the call to get(). The issue is that another thread could run in-between the call to empty() and the call to get(), stealing the item that empty() otherwise reported to exist. If empty() returns False it doesn't guarantee that a subsequent call to get() will not block. The reason that locking is needed is hinted at by the documentation for Queue.empty(): Indeed, this extra lock means that the threadsafe queue in the tutorial could be replaced with an old-fashioned non-threadsafe queue based on a simple list. In particular, the tutorial is using the threadsafe queue in a way that unfortunately requires an extra lock. I believe the tutorial you're following is a bad example of how to use Python's threadsafe queue. ![]() Thread = myThread(threadID, tName, workQueue) Print ("%s processing %s" % (threadName, data)) But in another tutorial, I've seen an example as following: import queue As the official tutorial goes, "The Queue class in this module implements all the required locking semantics". These functions work efficiently for performing operations in the end position.I've been gong through the tutorials about multithreading and queue in python3. for removing the element from the stack there is a pop() function that works the same according to the pop function in the queue. for inserting the element in the stack there is an append() function in the list that works the same according to the push function and for performing the pop operation i.e. In Python, there are some built-in functions that make the implementation of a stack using a list quite short and simple. Stack works on the principle of LIFO (Last in First out). Given below are the different ways to implement stack and queue in python: 1. There are specified classes of stack and queue in python. ![]() The operation for insertion of elements is known as enqueue operation and the operation for deletion of elements is known as dequeue operation. ![]() element which is inserted first will be removed first. Queue follows the principle of FIFO (First in First out) i.e. The operation for insertion of elements in stack is known as Push operation and the operation for deletion of element in stack is known as Pop operation. element which is inserted at last will be removed first. Stack follows the principle of LIFO (Last in First out) i.e. In data structures, stack and queue are part of linear data structure.
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