Allow up to n tasks to proceed simultaneously

A Semaphore is like a Condition, except that it does not broadcast its events. Each event is supplied to callbacks only until one "accepts" the event (by returning a true value).

Semaphore instances also have put() and take() methods that respectively increase or decrease their value by 1.

Note that Semaphore does not automatically decrease its count due to a callback or task resumption. You must explicitly take() the semaphore in your task or callback to reduce its count.

put ( self )

take ( self )