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<div class="section" id="module-eventlet.greenthread">
<h1><tt class="xref docutils literal"><span class="pre">greenthread</span></tt> – Green Thread Implementation<a class="headerlink" href="#module-eventlet.greenthread" title="Permalink to this headline">¶</a></h1>
<dl class="function">
<dt id="eventlet.greenthread.sleep">
<tt class="descclassname">eventlet.greenthread.</tt><tt class="descname">sleep</tt><big>(</big><em>seconds=0</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.sleep" title="Permalink to this definition">¶</a></dt>
<dd><p>Yield control to another eligible coroutine until at least <em>seconds</em> have
elapsed.</p>
<p><em>seconds</em> may be specified as an integer, or a float if fractional seconds
are desired. Calling <tt class="xref docutils literal"><span class="pre">sleep()</span></tt> with <em>seconds</em> of 0 is the
canonical way of expressing a cooperative yield. For example, if one is
looping over a large list performing an expensive calculation without
calling any socket methods, it’s a good idea to call <tt class="docutils literal"><span class="pre">sleep(0)</span></tt>
occasionally; otherwise nothing else will run.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn">
<tt class="descclassname">eventlet.greenthread.</tt><tt class="descname">spawn</tt><big>(</big><em>func</em>, <em>*args</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.spawn" title="Permalink to this definition">¶</a></dt>
<dd><p>Create a greenthread to run <tt class="docutils literal"><span class="pre">func(*args,</span> <span class="pre">**kwargs)</span></tt>. Returns a
<a title="eventlet.greenthread.GreenThread" class="reference internal" href="#eventlet.greenthread.GreenThread"><tt class="xref docutils literal"><span class="pre">GreenThread</span></tt></a> object which you can use to get the results of the
call.</p>
<p>Execution control returns immediately to the caller; the created greenthread
is merely scheduled to be run at the next available opportunity.
Use <a title="eventlet.greenthread.spawn_after" class="reference internal" href="#eventlet.greenthread.spawn_after"><tt class="xref docutils literal"><span class="pre">spawn_after()</span></tt></a> to arrange for greenthreads to be spawned
after a finite delay.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn_n">
<tt class="descclassname">eventlet.greenthread.</tt><tt class="descname">spawn_n</tt><big>(</big><em>func</em>, <em>*args</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.spawn_n" title="Permalink to this definition">¶</a></dt>
<dd><p>Same as <a title="eventlet.greenthread.spawn" class="reference internal" href="#eventlet.greenthread.spawn"><tt class="xref docutils literal"><span class="pre">spawn()</span></tt></a>, but returns a <tt class="docutils literal"><span class="pre">greenlet</span></tt> object from
which it is not possible to retrieve either a return value or
whether it raised any exceptions. This is faster than
<a title="eventlet.greenthread.spawn" class="reference internal" href="#eventlet.greenthread.spawn"><tt class="xref docutils literal"><span class="pre">spawn()</span></tt></a>; it is fastest if there are no keyword arguments.</p>
<p>If an exception is raised in the function, spawn_n prints a stack
trace; the print can be disabled by calling
<a title="eventlet.debug.hub_exceptions" class="reference external" href="debug.html#eventlet.debug.hub_exceptions"><tt class="xref docutils literal"><span class="pre">eventlet.debug.hub_exceptions()</span></tt></a> with False.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn_after">
<tt class="descclassname">eventlet.greenthread.</tt><tt class="descname">spawn_after</tt><big>(</big><em>seconds</em>, <em>func</em>, <em>*args</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.spawn_after" title="Permalink to this definition">¶</a></dt>
<dd><p>Spawns <em>func</em> after <em>seconds</em> have elapsed. It runs as scheduled even if
the current greenthread has completed.</p>
<p><em>seconds</em> may be specified as an integer, or a float if fractional seconds
are desired. The <em>func</em> will be called with the given <em>args</em> and
keyword arguments <em>kwargs</em>, and will be executed within its own greenthread.</p>
<p>The return value of <a title="eventlet.greenthread.spawn_after" class="reference internal" href="#eventlet.greenthread.spawn_after"><tt class="xref docutils literal"><span class="pre">spawn_after()</span></tt></a> is a <a title="eventlet.greenthread.GreenThread" class="reference internal" href="#eventlet.greenthread.GreenThread"><tt class="xref docutils literal"><span class="pre">GreenThread</span></tt></a> object,
which can be used to retrieve the results of the call.</p>
<p>To cancel the spawn and prevent <em>func</em> from being called,
call <a title="eventlet.greenthread.GreenThread.cancel" class="reference internal" href="#eventlet.greenthread.GreenThread.cancel"><tt class="xref docutils literal"><span class="pre">GreenThread.cancel()</span></tt></a> on the return value of <a title="eventlet.greenthread.spawn_after" class="reference internal" href="#eventlet.greenthread.spawn_after"><tt class="xref docutils literal"><span class="pre">spawn_after()</span></tt></a>.
This will not abort the function if it’s already started running, which is
generally the desired behavior. If terminating <em>func</em> regardless of whether
it’s started or not is the desired behavior, call <a title="eventlet.greenthread.GreenThread.kill" class="reference internal" href="#eventlet.greenthread.GreenThread.kill"><tt class="xref docutils literal"><span class="pre">GreenThread.kill()</span></tt></a>.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn_after_local">
<tt class="descclassname">eventlet.greenthread.</tt><tt class="descname">spawn_after_local</tt><big>(</big><em>seconds</em>, <em>func</em>, <em>*args</em>, <em>**kwargs</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.spawn_after_local" title="Permalink to this definition">¶</a></dt>
<dd><p>Spawns <em>func</em> after <em>seconds</em> have elapsed. The function will NOT be
called if the current greenthread has exited.</p>
<p><em>seconds</em> may be specified as an integer, or a float if fractional seconds
are desired. The <em>func</em> will be called with the given <em>args</em> and
keyword arguments <em>kwargs</em>, and will be executed within its own greenthread.</p>
<p>The return value of <a title="eventlet.greenthread.spawn_after" class="reference internal" href="#eventlet.greenthread.spawn_after"><tt class="xref docutils literal"><span class="pre">spawn_after()</span></tt></a> is a <a title="eventlet.greenthread.GreenThread" class="reference internal" href="#eventlet.greenthread.GreenThread"><tt class="xref docutils literal"><span class="pre">GreenThread</span></tt></a> object,
which can be used to retrieve the results of the call.</p>
<p>To cancel the spawn and prevent <em>func</em> from being called,
call <a title="eventlet.greenthread.GreenThread.cancel" class="reference internal" href="#eventlet.greenthread.GreenThread.cancel"><tt class="xref docutils literal"><span class="pre">GreenThread.cancel()</span></tt></a> on the return value. This will not abort the
function if it’s already started running. If terminating <em>func</em> regardless
of whether it’s started or not is the desired behavior, call
<a title="eventlet.greenthread.GreenThread.kill" class="reference internal" href="#eventlet.greenthread.GreenThread.kill"><tt class="xref docutils literal"><span class="pre">GreenThread.kill()</span></tt></a>.</p>
</dd></dl>
<dl class="class">
<dt id="eventlet.greenthread.GreenThread">
<em class="property">class </em><tt class="descclassname">eventlet.greenthread.</tt><tt class="descname">GreenThread</tt><big>(</big><em>parent</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.GreenThread" title="Permalink to this definition">¶</a></dt>
<dd><p>The GreenThread class is a type of Greenlet which has the additional
property of being able to retrieve the return value of the main function.
Do not construct GreenThread objects directly; call <a title="eventlet.greenthread.spawn" class="reference internal" href="#eventlet.greenthread.spawn"><tt class="xref docutils literal"><span class="pre">spawn()</span></tt></a> to get one.</p>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.cancel">
<tt class="descname">cancel</tt><big>(</big><em>*throw_args</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.GreenThread.cancel" title="Permalink to this definition">¶</a></dt>
<dd>Kills the greenthread using <a title="eventlet.greenthread.GreenThread.kill" class="reference internal" href="#eventlet.greenthread.GreenThread.kill"><tt class="xref docutils literal"><span class="pre">kill()</span></tt></a>, but only if it hasn’t
already started running. After being canceled,
all calls to <a title="eventlet.greenthread.GreenThread.wait" class="reference internal" href="#eventlet.greenthread.GreenThread.wait"><tt class="xref docutils literal"><span class="pre">wait()</span></tt></a> will raise <em>throw_args</em> (which default
to <tt class="xref docutils literal"><span class="pre">greenlet.GreenletExit</span></tt>).</dd></dl>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.kill">
<tt class="descname">kill</tt><big>(</big><em>*throw_args</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.GreenThread.kill" title="Permalink to this definition">¶</a></dt>
<dd>Kills the greenthread using <a title="eventlet.greenthread.GreenThread.kill" class="reference internal" href="#eventlet.greenthread.GreenThread.kill"><tt class="xref docutils literal"><span class="pre">kill()</span></tt></a>. After being killed
all calls to <a title="eventlet.greenthread.GreenThread.wait" class="reference internal" href="#eventlet.greenthread.GreenThread.wait"><tt class="xref docutils literal"><span class="pre">wait()</span></tt></a> will raise <em>throw_args</em> (which default
to <tt class="xref docutils literal"><span class="pre">greenlet.GreenletExit</span></tt>).</dd></dl>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.link">
<tt class="descname">link</tt><big>(</big><em>func</em>, <em>*curried_args</em>, <em>**curried_kwargs</em><big>)</big><a class="headerlink" href="#eventlet.greenthread.GreenThread.link" title="Permalink to this definition">¶</a></dt>
<dd><p>Set up a function to be called with the results of the GreenThread.</p>
<p>The function must have the following signature:</p>
<div class="highlight-python"><pre>def func(gt, [curried args/kwargs]):</pre>
</div>
<p>When the GreenThread finishes its run, it calls <em>func</em> with itself
and with the <a class="reference external" href="http://en.wikipedia.org/wiki/Currying">curried arguments</a> supplied at link-time. If the function wants
to retrieve the result of the GreenThread, it should call wait()
on its first argument.</p>
<p>Note that <em>func</em> is called within execution context of
the GreenThread, so it is possible to interfere with other linked
functions by doing things like switching explicitly to another
greenthread.</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.wait">
<tt class="descname">wait</tt><big>(</big><big>)</big><a class="headerlink" href="#eventlet.greenthread.GreenThread.wait" title="Permalink to this definition">¶</a></dt>
<dd>Returns the result of the main function of this GreenThread. If the
result is a normal return value, <a title="eventlet.greenthread.GreenThread.wait" class="reference internal" href="#eventlet.greenthread.GreenThread.wait"><tt class="xref docutils literal"><span class="pre">wait()</span></tt></a> returns it. If it raised
an exception, <a title="eventlet.greenthread.GreenThread.wait" class="reference internal" href="#eventlet.greenthread.GreenThread.wait"><tt class="xref docutils literal"><span class="pre">wait()</span></tt></a> will raise the same exception (though the
stack trace will unavoidably contain some frames from within the
greenthread module).</dd></dl>
</dd></dl>
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