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<H2>
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7.5.5 Event Objects
</H2>
<P>
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.
<P>
An event object manages an internal flag that can be set to true with
the <tt class="method">set()</tt> method and reset to false with the <tt class="method">clear()</tt> method. The
<tt class="method">wait()</tt> method blocks until the flag is true.
<P>
<dl><dt><b><a name='l2h-1656'><tt class='class'>Event</tt></a></b> ()
<dd>
The internal flag is initially false.
</dl>
<P>
<dl><dt><b><a name='l2h-1657'><tt class='method'>isSet</tt></a></b> ()
<dd>
Return true if and only if the internal flag is true.
</dl>
<P>
<dl><dt><b><a name='l2h-1658'><tt class='method'>set</tt></a></b> ()
<dd>
Set the internal flag to true.
All threads waiting for it to become true are awakened.
Threads that call <tt class="method">wait()</tt> once the flag is true will not block
at all.
</dl>
<P>
<dl><dt><b><a name='l2h-1659'><tt class='method'>clear</tt></a></b> ()
<dd>
Reset the internal flag to false.
Subsequently, threads calling <tt class="method">wait()</tt> will block until <tt class="method">set()</tt> is
called to set the internal flag to true again.
</dl>
<P>
<dl><dt><b><a name='l2h-1660'><tt class='method'>wait</tt></a></b> (<big>[</big><var>timeout</var><big>]</big>)
<dd>
Block until the internal flag is true.
If the internal flag is true on entry, return immediately. Otherwise,
block until another thread calls <tt class="method">set()</tt> to set the flag to
true, or until the optional timeout occurs.
<P>
When the timeout argument is present and not <code>None</code>, it should be a
floating point number specifying a timeout for the operation in
seconds (or fractions thereof).
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