sam-t2/devtools/v8plus/html/python/lib/event-objects.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="lib.html" title='Python Library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="thread-objects.html" />
<link rel="prev" href="semaphore-objects.html" />
<link rel="parent" href="module-threading.html" />
<link rel="next" href="thread-objects.html" />
<meta name='aesop' content='information' />
<title>7.5.5 Event Objects </title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="7.5.4.1 Semaphore Example"
  href="semaphore-examples.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="7.5 threading  "
  href="module-threading.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="7.5.6 Thread Objects"
  href="thread-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="semaphore-examples.html">7.5.4.1 Semaphore Example</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-threading.html">7.5 threading  </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="thread-objects.html">7.5.6 Thread Objects</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->

<H2><A NAME="SECTION009550000000000000000"></A><A NAME="event-objects"></A>
<BR>
7.5.5 Event Objects
</H2>

<P>
This is one of the simplest mechanisms for communication between
threads: one thread signals an event and other threads wait 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><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><span class="typelabel">class</span>&nbsp;<tt id='l2h-2733' xml:id='l2h-2733' class="class">Event</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
The internal flag is initially false.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2734' xml:id='l2h-2734' class="method">isSet</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Return true if and only if the internal flag is true.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2735' xml:id='l2h-2735' class="method">set</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<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><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2736' xml:id='l2h-2736' class="method">clear</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<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><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2737' xml:id='l2h-2737' class="method">wait</tt></b>(</nobr></td>
  <td><var></var><big>[</big><var>timeout</var><big>]</big><var></var>)</td></tr></table></dt>
<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).
</dl>

<P>

<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="7.5.4.1 Semaphore Example"
  href="semaphore-examples.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="7.5 threading  "
  href="module-threading.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="7.5.6 Thread Objects"
  href="thread-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="semaphore-examples.html">7.5.4.1 Semaphore Example</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-threading.html">7.5 threading  </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="thread-objects.html">7.5.6 Thread Objects</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>