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| 55 | <H1><A NAME="SECTION008500000000000000000"></A><A NAME="iterator"></A> |
| 56 | <BR> |
| 57 | 6.5 Iterator Protocol |
| 58 | </H1> |
| 59 | |
| 60 | <P> |
| 61 | |
| 62 | <span class="versionnote">New in version 2.2.</span> |
| 63 | |
| 64 | <P> |
| 65 | There are only a couple of functions specifically for working with |
| 66 | iterators. |
| 67 | |
| 68 | <P> |
| 69 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-346' xml:id='l2h-346' class="cfunction">PyIter_Check</tt></b>(</nobr></td><td>PyObject *<var>o</var>)</td></tr></table></dt> |
| 70 | <dd> |
| 71 | Return true if the object <var>o</var> supports the iterator protocol. |
| 72 | </dd></dl> |
| 73 | |
| 74 | <P> |
| 75 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-347' xml:id='l2h-347' class="cfunction">PyIter_Next</tt></b>(</nobr></td><td>PyObject *<var>o</var>)</td></tr></table></dt> |
| 76 | <dd> |
| 77 | <div class="refcount-info"> |
| 78 | <span class="label">Return value:</span> |
| 79 | <span class="value">New reference.</span> |
| 80 | </div> |
| 81 | Return the next value from the iteration <var>o</var>. If the object is |
| 82 | an iterator, this retrieves the next value from the iteration, and |
| 83 | returns <tt class="constant">NULL</tt> with no exception set if there are no remaining |
| 84 | items. If the object is not an iterator, <tt class="exception">TypeError</tt> is |
| 85 | raised, or if there is an error in retrieving the item, returns |
| 86 | <tt class="constant">NULL</tt> and passes along the exception. |
| 87 | </dd></dl> |
| 88 | |
| 89 | <P> |
| 90 | To write a loop which iterates over an iterator, the C code should |
| 91 | look something like this: |
| 92 | |
| 93 | <P> |
| 94 | <div class="verbatim"><pre> |
| 95 | PyObject *iterator = PyObject_GetIter(obj); |
| 96 | PyObject *item; |
| 97 | |
| 98 | if (iterator == NULL) { |
| 99 | /* propagate error */ |
| 100 | } |
| 101 | |
| 102 | while (item = PyIter_Next(iterator)) { |
| 103 | /* do something with item */ |
| 104 | ... |
| 105 | /* release reference when done */ |
| 106 | Py_DECREF(item); |
| 107 | } |
| 108 | |
| 109 | Py_DECREF(iterator); |
| 110 | |
| 111 | if (PyErr_Occurred()) { |
| 112 | /* propagate error */ |
| 113 | } |
| 114 | else { |
| 115 | /* continue doing useful work */ |
| 116 | } |
| 117 | </pre></div> |
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| 155 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
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