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<div class="section" id="module-eventlet.greenthread">
<span id="greenthread-green-thread-implementation"></span><h1><code class="xref py py-mod docutils literal"><span class="pre">greenthread</span></code> &#8211; 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">
<code class="descclassname">eventlet.greenthread.</code><code class="descname">sleep</code><span class="sig-paren">(</span><em>seconds=0</em><span class="sig-paren">)</span><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 <code class="xref py py-func docutils literal"><span class="pre">sleep()</span></code> 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&#8217;s a good idea to call <code class="docutils literal"><span class="pre">sleep(0)</span></code>
occasionally; otherwise nothing else will run.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn">
<code class="descclassname">eventlet.greenthread.</code><code class="descname">spawn</code><span class="sig-paren">(</span><em>func</em>, <em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenthread.spawn" title="Permalink to this definition"></a></dt>
<dd><p>Create a greenthread to run <code class="docutils literal"><span class="pre">func(*args,</span> <span class="pre">**kwargs)</span></code>. Returns a
<a class="reference internal" href="#eventlet.greenthread.GreenThread" title="eventlet.greenthread.GreenThread"><code class="xref py py-class docutils literal"><span class="pre">GreenThread</span></code></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 class="reference internal" href="#eventlet.greenthread.spawn_after" title="eventlet.greenthread.spawn_after"><code class="xref py py-func docutils literal"><span class="pre">spawn_after()</span></code></a> to arrange for greenthreads to be spawned
after a finite delay.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn_n">
<code class="descclassname">eventlet.greenthread.</code><code class="descname">spawn_n</code><span class="sig-paren">(</span><em>func</em>, <em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenthread.spawn_n" title="Permalink to this definition"></a></dt>
<dd><p>Same as <a class="reference internal" href="#eventlet.greenthread.spawn" title="eventlet.greenthread.spawn"><code class="xref py py-func docutils literal"><span class="pre">spawn()</span></code></a>, but returns a <code class="docutils literal"><span class="pre">greenlet</span></code> object from
which it is not possible to retrieve either a return value or
whether it raised any exceptions. This is faster than
<a class="reference internal" href="#eventlet.greenthread.spawn" title="eventlet.greenthread.spawn"><code class="xref py py-func docutils literal"><span class="pre">spawn()</span></code></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 class="reference internal" href="debug.html#eventlet.debug.hub_exceptions" title="eventlet.debug.hub_exceptions"><code class="xref py py-func docutils literal"><span class="pre">eventlet.debug.hub_exceptions()</span></code></a> with False.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.kill">
<code class="descclassname">eventlet.greenthread.</code><code class="descname">kill</code><span class="sig-paren">(</span><em>g</em>, <em>*throw_args</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenthread.kill" title="Permalink to this definition"></a></dt>
<dd><p>Terminates the target greenthread by raising an exception into it.
Whatever that greenthread might be doing; be it waiting for I/O or another
primitive, it sees an exception right away.</p>
<p>By default, this exception is GreenletExit, but a specific exception
may be specified. <em>throw_args</em> should be the same as the arguments to
raise; either an exception instance or an exc_info tuple.</p>
<p>Calling <a class="reference internal" href="#eventlet.greenthread.kill" title="eventlet.greenthread.kill"><code class="xref py py-func docutils literal"><span class="pre">kill()</span></code></a> causes the calling greenthread to cooperatively yield.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn_after">
<code class="descclassname">eventlet.greenthread.</code><code class="descname">spawn_after</code><span class="sig-paren">(</span><em>seconds</em>, <em>func</em>, <em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><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 class="reference internal" href="#eventlet.greenthread.spawn_after" title="eventlet.greenthread.spawn_after"><code class="xref py py-func docutils literal"><span class="pre">spawn_after()</span></code></a> is a <a class="reference internal" href="#eventlet.greenthread.GreenThread" title="eventlet.greenthread.GreenThread"><code class="xref py py-class docutils literal"><span class="pre">GreenThread</span></code></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 class="reference internal" href="#eventlet.greenthread.GreenThread.cancel" title="eventlet.greenthread.GreenThread.cancel"><code class="xref py py-meth docutils literal"><span class="pre">GreenThread.cancel()</span></code></a> on the return value of <a class="reference internal" href="#eventlet.greenthread.spawn_after" title="eventlet.greenthread.spawn_after"><code class="xref py py-func docutils literal"><span class="pre">spawn_after()</span></code></a>.
This will not abort the function if it&#8217;s already started running, which is
generally the desired behavior. If terminating <em>func</em> regardless of whether
it&#8217;s started or not is the desired behavior, call <a class="reference internal" href="#eventlet.greenthread.GreenThread.kill" title="eventlet.greenthread.GreenThread.kill"><code class="xref py py-meth docutils literal"><span class="pre">GreenThread.kill()</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt id="eventlet.greenthread.spawn_after_local">
<code class="descclassname">eventlet.greenthread.</code><code class="descname">spawn_after_local</code><span class="sig-paren">(</span><em>seconds</em>, <em>func</em>, <em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><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 class="reference internal" href="#eventlet.greenthread.spawn_after" title="eventlet.greenthread.spawn_after"><code class="xref py py-func docutils literal"><span class="pre">spawn_after()</span></code></a> is a <a class="reference internal" href="#eventlet.greenthread.GreenThread" title="eventlet.greenthread.GreenThread"><code class="xref py py-class docutils literal"><span class="pre">GreenThread</span></code></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 class="reference internal" href="#eventlet.greenthread.GreenThread.cancel" title="eventlet.greenthread.GreenThread.cancel"><code class="xref py py-meth docutils literal"><span class="pre">GreenThread.cancel()</span></code></a> on the return value. This will not abort the
function if it&#8217;s already started running. If terminating <em>func</em> regardless
of whether it&#8217;s started or not is the desired behavior, call
<a class="reference internal" href="#eventlet.greenthread.GreenThread.kill" title="eventlet.greenthread.GreenThread.kill"><code class="xref py py-meth docutils literal"><span class="pre">GreenThread.kill()</span></code></a>.</p>
</dd></dl>
<dl class="class">
<dt id="eventlet.greenthread.GreenThread">
<em class="property">class </em><code class="descclassname">eventlet.greenthread.</code><code class="descname">GreenThread</code><span class="sig-paren">(</span><em>parent</em><span class="sig-paren">)</span><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 class="reference internal" href="#eventlet.greenthread.spawn" title="eventlet.greenthread.spawn"><code class="xref py py-func docutils literal"><span class="pre">spawn()</span></code></a> to get one.</p>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.cancel">
<code class="descname">cancel</code><span class="sig-paren">(</span><em>*throw_args</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenthread.GreenThread.cancel" title="Permalink to this definition"></a></dt>
<dd><p>Kills the greenthread using <a class="reference internal" href="#eventlet.greenthread.kill" title="eventlet.greenthread.kill"><code class="xref py py-func docutils literal"><span class="pre">kill()</span></code></a>, but only if it hasn&#8217;t
already started running. After being canceled,
all calls to <a class="reference internal" href="#eventlet.greenthread.GreenThread.wait" title="eventlet.greenthread.GreenThread.wait"><code class="xref py py-meth docutils literal"><span class="pre">wait()</span></code></a> will raise <em>throw_args</em> (which default
to <code class="xref py py-class docutils literal"><span class="pre">greenlet.GreenletExit</span></code>).</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.kill">
<code class="descname">kill</code><span class="sig-paren">(</span><em>*throw_args</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenthread.GreenThread.kill" title="Permalink to this definition"></a></dt>
<dd><p>Kills the greenthread using <a class="reference internal" href="#eventlet.greenthread.kill" title="eventlet.greenthread.kill"><code class="xref py py-func docutils literal"><span class="pre">kill()</span></code></a>. After being killed
all calls to <a class="reference internal" href="#eventlet.greenthread.GreenThread.wait" title="eventlet.greenthread.GreenThread.wait"><code class="xref py py-meth docutils literal"><span class="pre">wait()</span></code></a> will raise <em>throw_args</em> (which default
to <code class="xref py py-class docutils literal"><span class="pre">greenlet.GreenletExit</span></code>).</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.link">
<code class="descname">link</code><span class="sig-paren">(</span><em>func</em>, <em>*curried_args</em>, <em>**curried_kwargs</em><span class="sig-paren">)</span><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"><div class="highlight"><pre>def func(gt, [curried args/kwargs]):
</pre></div>
</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.unlink">
<code class="descname">unlink</code><span class="sig-paren">(</span><em>func</em>, <em>*curried_args</em>, <em>**curried_kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenthread.GreenThread.unlink" title="Permalink to this definition"></a></dt>
<dd><p>remove linked function set by <a class="reference internal" href="#eventlet.greenthread.GreenThread.link" title="eventlet.greenthread.GreenThread.link"><code class="xref py py-meth docutils literal"><span class="pre">link()</span></code></a></p>
<p>Remove successfully return True, otherwise False</p>
</dd></dl>
<dl class="method">
<dt id="eventlet.greenthread.GreenThread.wait">
<code class="descname">wait</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#eventlet.greenthread.GreenThread.wait" title="Permalink to this definition"></a></dt>
<dd><p>Returns the result of the main function of this GreenThread. If the
result is a normal return value, <a class="reference internal" href="#eventlet.greenthread.GreenThread.wait" title="eventlet.greenthread.GreenThread.wait"><code class="xref py py-meth docutils literal"><span class="pre">wait()</span></code></a> returns it. If it raised
an exception, <a class="reference internal" href="#eventlet.greenthread.GreenThread.wait" title="eventlet.greenthread.GreenThread.wait"><code class="xref py py-meth docutils literal"><span class="pre">wait()</span></code></a> will raise the same exception (though the
stack trace will unavoidably contain some frames from within the
greenthread module).</p>
</dd></dl>
</dd></dl>
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