threads and concurrency the kind of signaling shown in this example is often instead carried out using condition variableswhich will be described shortly events events are used to communicate between threads one thread signals an "event,and one or more other threads wait for it an event instance manages an internal flag that can be set to true with the set(method and reset to false with the clear(method the wait(method blocks until the flag is true event(creates new event instance with the internal flag set to false an event instanceesupports the following methodse is_set(returns true only if the internal flag is true this method is called isset(in older code set(sets the internal flag to true all threads waiting for it to become true are awakened clear(resets the internal flag to false wait([timeout]blocks until the internal flag is true if the internal flag is true on entrythis method returns immediately otherwiseit blocks until another thread calls set(to set the flag to true or until the optional timeout occurs timeout is floating-point number specifying timeout period in seconds although event objects can be used to signal other threadsthey should not be used to implement the kind of notification that is typical in producer/consumer problems for exampleyou should avoid code like thisevt event(def producer()while trueproduce item evt signal(def consumer()while truewait for an item evt wait(consume the item clear the event and wait again evt clear(this code does not work reliably because the producer might produce new item in between the evt wait(and evt clear(operations howeverby clearing the eventthis new item won' be seen by the consumer until the producer creates new item in the best casethe program will experience minor hiccup where the processing lib fl ff