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<title>6.5 Iterator Protocol </title>
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<H1><A NAME="SECTION008500000000000000000"></A><A NAME="iterator"></A>
<BR>
6.5 Iterator Protocol
</H1>
<P>
<span class="versionnote">New in version 2.2.</span>
<P>
There are only a couple of functions specifically for working with
iterators.
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-345' xml:id='l2h-345' class="cfunction">PyIter_Check</tt></b>(</nobr></td><td>PyObject *<var>o</var>)</td></tr></table></dt>
<dd>
Return true if the object <var>o</var> supports the iterator protocol.
</dd></dl>
<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-346' xml:id='l2h-346' class="cfunction">PyIter_Next</tt></b>(</nobr></td><td>PyObject *<var>o</var>)</td></tr></table></dt>
<dd>
<div class="refcount-info">
<span class="label">Return value:</span>
<span class="value">New reference.</span>
</div>
Return the next value from the iteration <var>o</var>. If the object is
an iterator, this retrieves the next value from the iteration, and
returns <tt class="constant">NULL</tt> with no exception set if there are no remaining
items. If the object is not an iterator, <tt class="exception">TypeError</tt> is
raised, or if there is an error in retrieving the item, returns
<tt class="constant">NULL</tt> and passes along the exception.
</dd></dl>
<P>
To write a loop which iterates over an iterator, the C code should
look something like this:
<P>
<div class="verbatim"><pre>
PyObject *iterator = PyObject_GetIter(obj);
PyObject *item;
if (iterator == NULL) {
/* propagate error */
}
while (item = PyIter_Next(iterator)) {
/* do something with item */
...
/* release reference when done */
Py_DECREF(item);
}
Py_DECREF(iterator);
if (PyErr_Occurred()) {
/* propagate error */
}
else {
/* continue doing useful work */
}
</pre></div>
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<span class="release-info">Release 2.4.3, documentation updated on 29 March 2006.</span>
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