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55 | <H2><A NAME="SECTION009580000000000000000"></A><A NAME="weakref-objects"></A> | |
56 | <BR> | |
57 | 7.5.8 Weak Reference Objects | |
58 | </H2> | |
59 | ||
60 | <P> | |
61 | Python supports <em>weak references</em> as first-class objects. There | |
62 | are two specific object types which directly implement weak | |
63 | references. The first is a simple reference object, and the second | |
64 | acts as a proxy for the original object as much as it can. | |
65 | ||
66 | <P> | |
67 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-718' xml:id='l2h-718' class="cfunction">PyWeakref_Check</tt></b>(</nobr></td><td>ob)</td></tr></table></dt> | |
68 | <dd> | |
69 | Return true if <var>ob</var> is either a reference or proxy object. | |
70 | ||
71 | <span class="versionnote">New in version 2.2.</span> | |
72 | ||
73 | </dd></dl> | |
74 | ||
75 | <P> | |
76 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-719' xml:id='l2h-719' class="cfunction">PyWeakref_CheckRef</tt></b>(</nobr></td><td>ob)</td></tr></table></dt> | |
77 | <dd> | |
78 | Return true if <var>ob</var> is a reference object. | |
79 | ||
80 | <span class="versionnote">New in version 2.2.</span> | |
81 | ||
82 | </dd></dl> | |
83 | ||
84 | <P> | |
85 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>int <b><tt id='l2h-720' xml:id='l2h-720' class="cfunction">PyWeakref_CheckProxy</tt></b>(</nobr></td><td>ob)</td></tr></table></dt> | |
86 | <dd> | |
87 | Return true if <var>ob</var> is a proxy object. | |
88 | ||
89 | <span class="versionnote">New in version 2.2.</span> | |
90 | ||
91 | </dd></dl> | |
92 | ||
93 | <P> | |
94 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-721' xml:id='l2h-721' class="cfunction">PyWeakref_NewRef</tt></b>(</nobr></td><td>PyObject *<var>ob</var>, | |
95 | PyObject *<var>callback</var>)</td></tr></table></dt> | |
96 | <dd> | |
97 | <div class="refcount-info"> | |
98 | <span class="label">Return value:</span> | |
99 | <span class="value">New reference.</span> | |
100 | </div> | |
101 | Return a weak reference object for the object <var>ob</var>. This will | |
102 | always return a new reference, but is not guaranteed to create a new | |
103 | object; an existing reference object may be returned. The second | |
104 | parameter, <var>callback</var>, can be a callable object that receives | |
105 | notification when <var>ob</var> is garbage collected; it should accept a | |
106 | single parameter, which will be the weak reference object itself. | |
107 | <var>callback</var> may also be <code>None</code> or <tt class="constant">NULL</tt>. If <var>ob</var> | |
108 | is not a weakly-referencable object, or if <var>callback</var> is not | |
109 | callable, <code>None</code>, or <tt class="constant">NULL</tt>, this will return <tt class="constant">NULL</tt> and | |
110 | raise <tt class="exception">TypeError</tt>. | |
111 | ||
112 | <span class="versionnote">New in version 2.2.</span> | |
113 | ||
114 | </dd></dl> | |
115 | ||
116 | <P> | |
117 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-722' xml:id='l2h-722' class="cfunction">PyWeakref_NewProxy</tt></b>(</nobr></td><td>PyObject *<var>ob</var>, | |
118 | PyObject *<var>callback</var>)</td></tr></table></dt> | |
119 | <dd> | |
120 | <div class="refcount-info"> | |
121 | <span class="label">Return value:</span> | |
122 | <span class="value">New reference.</span> | |
123 | </div> | |
124 | Return a weak reference proxy object for the object <var>ob</var>. This | |
125 | will always return a new reference, but is not guaranteed to create | |
126 | a new object; an existing proxy object may be returned. The second | |
127 | parameter, <var>callback</var>, can be a callable object that receives | |
128 | notification when <var>ob</var> is garbage collected; it should accept a | |
129 | single parameter, which will be the weak reference object itself. | |
130 | <var>callback</var> may also be <code>None</code> or <tt class="constant">NULL</tt>. If <var>ob</var> is not | |
131 | a weakly-referencable object, or if <var>callback</var> is not callable, | |
132 | <code>None</code>, or <tt class="constant">NULL</tt>, this will return <tt class="constant">NULL</tt> and raise | |
133 | <tt class="exception">TypeError</tt>. | |
134 | ||
135 | <span class="versionnote">New in version 2.2.</span> | |
136 | ||
137 | </dd></dl> | |
138 | ||
139 | <P> | |
140 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-723' xml:id='l2h-723' class="cfunction">PyWeakref_GetObject</tt></b>(</nobr></td><td>PyObject *<var>ref</var>)</td></tr></table></dt> | |
141 | <dd> | |
142 | <div class="refcount-info"> | |
143 | <span class="label">Return value:</span> | |
144 | <span class="value">Borrowed reference.</span> | |
145 | </div> | |
146 | Return the referenced object from a weak reference, <var>ref</var>. If | |
147 | the referent is no longer live, returns <code>None</code>. | |
148 | ||
149 | <span class="versionnote">New in version 2.2.</span> | |
150 | ||
151 | </dd></dl> | |
152 | ||
153 | <P> | |
154 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"><td><nobr>PyObject* <b><tt id='l2h-724' xml:id='l2h-724' class="cfunction">PyWeakref_GET_OBJECT</tt></b>(</nobr></td><td>PyObject *<var>ref</var>)</td></tr></table></dt> | |
155 | <dd> | |
156 | <div class="refcount-info"> | |
157 | <span class="label">Return value:</span> | |
158 | <span class="value">Borrowed reference.</span> | |
159 | </div> | |
160 | Similar to <tt class="cfunction">PyWeakref_GetObject()</tt>, but implemented as a | |
161 | macro that does no error checking. | |
162 | ||
163 | <span class="versionnote">New in version 2.2.</span> | |
164 | ||
165 | </dd></dl> | |
166 | ||
167 | <P> | |
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