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<a href="twisted.html">Package twisted</a> ::
<a href="twisted.internet.html">Package internet</a> ::
Module defer
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<!-- =========== START OF MODULE DESCRIPTION =========== -->
<h2 class="module">Module twisted.internet.defer</h2>
<p>Support for results that aren't immediately available.</p>
<p>API Stability: stable</p>
Maintainer: <a href="mailto:glyph@twistedmatrix.com">Glyph
Lefkowitz</a>
<hr/>
<!-- =========== START OF CLASSES =========== -->
<table class="summary" border="1" cellpadding="3" cellspacing="0" width="100%" bgcolor="white">
<tr bgcolor="#70b0f0" class="summary">
<th colspan="2">Classes</th></tr>
<tr><td width="15%">
<b><a href="twisted.internet.defer._nothing.html"><code>_nothing</code></a></b></td>
<td> </td></tr>
<tr><td width="15%">
<b><a href="twisted.internet.defer.Deferred.html"><code>Deferred</code></a></b></td>
<td>This is a callback which will be put off until later.</td></tr>
<tr><td width="15%">
<b><a href="twisted.internet.defer.DeferredList.html"><code>DeferredList</code></a></b></td>
<td>I combine a group of deferreds into one callback.</td></tr>
</table><br />
<!-- =========== START OF EXCEPTIONS =========== -->
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<th colspan="2">Exceptions</th></tr>
<tr><td width="15%">
<b><a href="twisted.internet.defer.AlreadyArmedError.html"><code>AlreadyArmedError</code></a></b></td>
<td> </td></tr>
<tr><td width="15%">
<b><a href="twisted.internet.defer.AlreadyCalledError.html"><code>AlreadyCalledError</code></a></b></td>
<td> </td></tr>
<tr><td width="15%">
<b><a href="twisted.internet.defer.TimeoutError.html"><code>TimeoutError</code></a></b></td>
<td> </td></tr>
</table><br />
<!-- =========== START OF FUNCTION SUMMARY =========== -->
<table class="summary" border="1" cellpadding="3" cellspacing="0" width="100%" bgcolor="white">
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<th colspan="2">Function Summary</th></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> </font></td>
<td><code><a name="_parseDListResult"></a><span class="summary-sig"><span class="summary-sig-name">_parseDListResult</span>(<span class=summary-sig-arg>l</span>,
<span class=summary-sig-arg>fireOnOneErrback</span>)</span></code>
</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> </font></td>
<td><code><span class="summary-sig"><a href="twisted.internet.defer.html#execute" class="summary-sig-name"><code>execute</code></a>(<span class=summary-sig-arg>callable</span>,
<span class="summary-sig-vararg">*args</span>,
<span class="summary-sig-kwarg">**kw</span>)</span></code>
<br />
Create a deferred from a callable and arguments.</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> <a href="twisted.internet.defer.Deferred.html"
class="link"><code>Deferred</code></a>
</font></td>
<td><code><span class="summary-sig"><a href="twisted.internet.defer.html#fail" class="summary-sig-name"><code>fail</code></a>(<span class=summary-sig-arg>result</span>)</span></code>
<br />
Return a Deferred that has already had '.errback(result)' called.</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> </font></td>
<td><code><span class="summary-sig"><a href="twisted.internet.defer.html#gatherResults" class="summary-sig-name"><code>gatherResults</code></a>(<span class=summary-sig-arg>deferredList</span>,
<span class=summary-sig-arg>fireOnOneErrback</span>)</span></code>
<br />
Returns list with result of given Deferreds.</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> </font></td>
<td><code><a name="logError"></a><span class="summary-sig"><span class="summary-sig-name">logError</span>(<span class=summary-sig-arg>err</span>)</span></code>
</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> <code>Deferred</code>
</font></td>
<td><code><span class="summary-sig"><a href="twisted.internet.defer.html#maybeDeferred" class="summary-sig-name"><code>maybeDeferred</code></a>(<span class=summary-sig-arg>f</span>,
<span class="summary-sig-vararg">*args</span>,
<span class="summary-sig-kwarg">**kw</span>)</span></code>
<br />
Invoke a function that may or may not return a deferred.</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> </font></td>
<td><code><a name="passthru"></a><span class="summary-sig"><span class="summary-sig-name">passthru</span>(<span class=summary-sig-arg>arg</span>)</span></code>
</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> <a href="twisted.internet.defer.Deferred.html"
class="link"><code>Deferred</code></a>
</font></td>
<td><code><span class="summary-sig"><a href="twisted.internet.defer.html#succeed" class="summary-sig-name"><code>succeed</code></a>(<span class=summary-sig-arg>result</span>)</span></code>
<br />
Return a Deferred that has already had '.callback(result)' called.</td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"> </font></td>
<td><code><a name="timeout"></a><span class="summary-sig"><span class="summary-sig-name">timeout</span>(<span class=summary-sig-arg>deferred</span>)</span></code>
</td></tr>
</table><br />
<!-- =========== START OF VARIABLE SUMMARY =========== -->
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<tr bgcolor="#70b0f0" class="summary">
<th colspan="2">Variable Summary</th></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"><code>int</code></font></td>
<td><b><a href="twisted.internet.defer.html#FAILURE"><code>FAILURE</code></a></b> = <span title="0">0 </span></td></tr>
<tr><td align="right" valign="top" width="15%"><font size="-1"><code>int</code></font></td>
<td><b><a href="twisted.internet.defer.html#SUCCESS"><code>SUCCESS</code></a></b> = <span title="1">1 </span></td></tr>
</table><br />
<!-- =========== START OF FUNCTION DETAILS =========== -->
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<tr bgcolor="#70b0f0" class="details">
<th colspan="2">Function Details</th></tr>
</table>
<a name="execute"></a>
<table width="100%" class="func-details" bgcolor="#e0e0e0"><tr><td>
<h3><span class="sig"><span class="sig-name">execute</span>(<span class=sig-arg>callable</span>,
<span class="sig-vararg">*args</span>,
<span class="sig-kwarg">**kw</span>)</span>
</h3>
<p>Create a deferred from a callable and arguments.</p>
Call the given function with the given arguments. Return a deferred
which has been fired with its callback as the result of that invocation
or its errback with a Failure for the exception thrown.
<dl><dt></dt><dd>
</dd></dl>
</td></tr></table>
<a name="fail"></a>
<table width="100%" class="func-details" bgcolor="#e0e0e0"><tr><td>
<h3><span class="sig"><span class="sig-name">fail</span>(<span class=sig-arg>result</span>=<span class=sig-default><class twisted.internet.defer._nothing at 0x82a9674></span>)</span>
</h3>
<p>Return a Deferred that has already had '.errback(result)'
called.</p>
See <a href="twisted.internet.defer.html#succeed"
class="link"><code>succeed</code></a>'s docstring for rationale.
<dl><dt></dt><dd>
<dl><dt><b>Parameters:</b></dt>
<dd><code><b>result</b></code> -
The same argument that <a
href="twisted.internet.defer.Deferred.html#errback"
class="link"><code>Deferred.errback</code></a> takes.
</dd>
</dl>
<dl><dt><b>Returns:</b></dt>
<dd>
<a href="twisted.internet.defer.Deferred.html"
class="link"><code>Deferred</code></a>
</dd>
</dl>
</dd></dl>
</td></tr></table>
<a name="gatherResults"></a>
<table width="100%" class="func-details" bgcolor="#e0e0e0"><tr><td>
<h3><span class="sig"><span class="sig-name">gatherResults</span>(<span class=sig-arg>deferredList</span>,
<span class=sig-arg>fireOnOneErrback</span>=<span class=sig-default>0</span>)</span>
</h3>
<p>Returns list with result of given Deferreds.</p>
This builds on <code>DeferredList</code> but is useful since you
don't need to parse the result for success/failure.
<dl><dt></dt><dd>
<dl><dt><b>Parameters:</b></dt>
<dd><code><b>deferredList</b></code>
<br /><i>
(type=<code>list</code> of <a
href="twisted.internet.defer.Deferred.html"
class="link"><code>Deferred</code></a>s)</i>
</dd>
</dl>
</dd></dl>
</td></tr></table>
<a name="maybeDeferred"></a>
<table width="100%" class="func-details" bgcolor="#e0e0e0"><tr><td>
<h3><span class="sig"><span class="sig-name">maybeDeferred</span>(<span class=sig-arg>f</span>,
<span class="sig-vararg">*args</span>,
<span class="sig-kwarg">**kw</span>)</span>
</h3>
<p>Invoke a function that may or may not return a deferred.</p>
Call the given function with the given arguments. If the returned
object is a <code>Deferred</code>, return it. If the returned object is
a <code>Failure</code>, wrap it with <code>fail</code> and return it.
Otherwise, wrap it in <code>succeed</code> and return it. If an
exception is raised, convert it to a <code>Failure</code>, wrap it in
<code>fail</code>, and then return it.
<dl><dt></dt><dd>
<dl><dt><b>Parameters:</b></dt>
<dd><code><b>f</b></code> -
The callable to invoke
<br /><i>
(type=Any callable)</i>
<dd><code><b>args</b></code> -
The arguments to pass to <code>f</code>
<dd><code><b>kw</b></code> -
The keyword arguments to pass to <code>f</code>
</dd>
</dl>
<dl><dt><b>Returns:</b></dt>
<dd>
<p>The result of the function call, wrapped in a
<code>Deferred</code> if necessary.</p>
API Stability: Unstable
<br /><i>
(type=<code>Deferred</code>)</i>
</dd>
</dl>
</dd></dl>
</td></tr></table>
<a name="succeed"></a>
<table width="100%" class="func-details" bgcolor="#e0e0e0"><tr><td>
<h3><span class="sig"><span class="sig-name">succeed</span>(<span class=sig-arg>result</span>)</span>
</h3>
<p>Return a Deferred that has already had '.callback(result)'
called.</p>
<p>This is useful when you're writing synchronous code to an
asynchronous interface: i.e., some code is calling you expecting a
Deferred result, but you don't actually need to do anything
asynchronous. Just return defer.succeed(theResult).</p>
See <a href="twisted.internet.defer.html#fail"
class="link"><code>fail</code></a> for a version of this function that
uses a failing Deferred rather than a successful one.
<dl><dt></dt><dd>
<dl><dt><b>Parameters:</b></dt>
<dd><code><b>result</b></code> -
The result to give to the Deferred's 'callback' method.
</dd>
</dl>
<dl><dt><b>Returns:</b></dt>
<dd>
<a href="twisted.internet.defer.Deferred.html"
class="link"><code>Deferred</code></a>
</dd>
</dl>
</dd></dl>
</td></tr></table>
<br />
<!-- =========== START OF VARIABLE DETAILS =========== -->
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<tr bgcolor="#70b0f0" class="details">
<th colspan="2">Variable Details</th></tr>
</table>
<table width="100%" class="var-details" bgcolor="#e0e0e0"><tr><td>
<a name="FAILURE"></a>
<h3>FAILURE</h3>
<dl>
<dt></dt>
<dd>
<dl>
<dt><b>Type:</b></dt>
<dd>
<code>int</code>
</dd>
<span title="0"> <dt><b>Value:</b></dt>
<dd><table><tr><td>
<pre class="variable">
0 </pre>
</td></tr></table></dd>
</span> </dl>
</dd>
</dl></td></tr></table>
<table width="100%" class="var-details" bgcolor="#e0e0e0"><tr><td>
<a name="SUCCESS"></a>
<h3>SUCCESS</h3>
<dl>
<dt></dt>
<dd>
<dl>
<dt><b>Type:</b></dt>
<dd>
<code>int</code>
</dd>
<span title="1"> <dt><b>Value:</b></dt>
<dd><table><tr><td>
<pre class="variable">
1 </pre>
</td></tr></table></dd>
</span> </dl>
</dd>
</dl></td></tr></table>
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