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54 | ||
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> | |
118 | ||
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155 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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