inter thread/process synchronisation the output from an example run of this program ismain starting main creating the dataresource object dataresource initialising the empty data dataresource setting up the condition object main create the consumer threads main create the producer thread main starting consumer threads dataresource starting consumer method in consumer dataresource starting consumer method in consumer main starting producer thread dataresource starting producer method dataresource producer setting data main done dataresource producer notifying all waiting threads dataresource resource is available to consumer dataresource data read in consumer dataresource resource is available to consumer dataresource data read in consumer python semaphores the python semaphore class implements dijkstra' counting semaphore model in generala semaphore is like an integer variableits value is intended to represent number of available resources of some kind there are typically two operations available on semaphorethese operations are acquire(and release((although in some libraries dijkstra' original names of (and (are usedthese operation names are based on the original dutch phrasesthe acquire(operation subtracts one from the value of the semaphoreunless the value is in which case it blocks the calling thread until the semaphore' value increases above again the signal(operation adds one to the valueindicating new instance of the resource has been added to the pool both the threading semaphore and the multiprocessing semaphore classes also supports the context management protocol an optional parameter used with the semaphore constructor gives the initial value for the internal counterit defaults to if the value given is less than valueerror is raised the following example illustrates different threads all running the same worker(function the worker(function attempts to acquire semaphoreif it does then it continues into the with statement blockif it doesn'tit waits until it can acquire it as the semaphore is initialised to there can only be two threads that can acquire the semaphore at time