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(python2.1-lib.info)Event Objects

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Event Objects
-------------

This is one of the simplest mechanisms for communication between
threads: one thread signals an event and one or more other threads are
waiting for it.

An event object 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()'
     The internal flag is initially false.

`isSet()'
     Return true if and only if the internal flag is true.

`set()'
     Set the internal flag to true.  All threads waiting for it to
     become true are awakened.  Threads that call `wait()' once the
     flag is true will not block at all.

`clear()'
     Reset the internal flag to false.  Subsequently, threads calling
     `wait()' will block until `set()' is called to set the internal
     flag to true again.

`wait([timeout])'
     Block until the internal flag is true.  If the internal flag is
     true on entry, return immediately.  Otherwise, block until another
     thread calls `set()' to set the flag to true, or until the
     optional timeout occurs.

     When the timeout argument is present and not `None', it should be a
     floating point number specifying a timeout for the operation in
     seconds (or fractions thereof).