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Ralf W. Grosse-Kunstleve
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See Python C++-SIG thread: "object.attr(object& attrname) proposal"
Started 2008-05-25 by hohehohe2@gmail.com. Excerpts: If char const* is passed to objecjt.attr(), it uses PyObject_GetAttrStrng() or PyObject_SetAttrStrng(). If object is passed to objecjt.attr(), it takes the object as a Python string object and uses PyObject_GetAttr() or PyObject_SetAttr(). If attr() behaves like this, it can be useful when there are lots of objects which you know have the same attribute name. You can save time by first making a boost::python::object and passing it to every object's attr() inside a loop. I just made a bit of modification to boost:python locally and did a quick test, like test 1: for(int i = 0; i < n; ++i) { omain.attr(attrname) = 444; //attrname is a char const* } test 2: for(int i = 0; i < n; ++i) { object o = omain.attr(attrname); //attrname is a char const* } test 3: for(int i = 0; i < n; ++i) { omain.attr(oaaaa) = 444; //oaaaa is boost::python::object that represents a string } test 4: for(int i = 0; i < n; ++i) { object o = omain.attr(oaaaa); //oaaaa is boost::python::object that represents a string } and it reasonably reflected the difference between PyObject_*Attr() and PyObject_*AttrString. test 1 :2783ms test 2 :2357ms test 3 :1882ms test 4 :1267ms test5: PyObject_SetAttrString(po_main, "aaaa", po_num444); test6: Py_DECREF(PyObject_GetAttrString(po_main, "aaaa")); test7: PyObject_SetAttr(po_main, po_aaaa, po_num444); test8: Py_DECREF(PyObject_GetAttr(po_main, po_aaaa)); (po_ prefixed variables are PyObject*), all inside each for loop, and the results were test 5 :2410ms test 6 :2277ms test 7 :1629ms test 8 :1094ms It's boost 1.35.0, Python 2.5 on linux(gcc4.1.2). I also did the same test on windows(vs8) and the tendency was not so different. [SVN r45918]
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‎doc/v2/object.html‎

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@@ -74,6 +74,32 @@ <h2>Contents</h2>
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</dl>
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</dd>
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<dt><a href="#const_objattribute_policies-spec">Class
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<code>const_objattribute_policies</code></a></dt>
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<dd>
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<dl class="page-index">
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<dt><a href="#const_objattribute_policies-spec-synopsis">Class
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<code>const_objattribute_policies</code> synopsis</a></dt>
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<dt><a href="#const_objattribute_policies-spec-statics">Class
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<code>const_objattribute_policies</code> static functions</a></dt>
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</dl>
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</dd>
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<dt><a href="#objattribute_policies-spec">Class
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<code>objattribute_policies</code></a></dt>
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<dd>
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<dl class="page-index">
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<dt><a href="#objattribute_policies-spec-synopsis">Class
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<code>objattribute_policies</code> synopsis</a></dt>
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<dt><a href="#objattribute_policies-spec-statics">Class
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<code>objattribute_policies</code> static functions</a></dt>
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</dl>
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</dd>
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<dt><a href="#const_item_policies-spec">Class
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<code>const_item_policies</code></a></dt>
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<!-- end -->
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<!-- begin -->
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<h3><a name="const_objattribute_policies-spec"></a>Class
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<code>const_objattribute_policies</code></h3>
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<p>The policies which are used for proxies representing an attribute
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access to a <code>const&nbsp;object</code> when the attribute name is
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given as a <code>const&nbsp;object</code>.</p>
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<h4><a name="const_objattribute_policies-spec-synopsis"></a>Class
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<code>const_objattribute_policies</code> synopsis</h4>
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<pre>
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namespace boost { namespace python { namespace api
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{
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struct const_objattribute_policies
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{
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typedef object const& key_type;
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static object get(object const&amp; target, object const& key);
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};
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}}}
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</pre>
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<h4><a name="const_objattribute_policies-spec-statics"></a>Class
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<code>const_objattribute_policies</code> static functions</h4>
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<pre>
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static object get(object const&amp; target, object const& key);
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> <code>key</code> is an <code>object</code>
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holding a string.</dt>
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<dt><b>Effects:</b> accesses the attribute of <code>target</code> named
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by <code>key</code>.</dt>
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<dt><b>Returns:</b> An <code>object</code> managing the result of the
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attribute access.</dt>
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<dt><b>Throws:</b> <code><a href=
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"errors.html#error_already_set-spec">error_already_set</a></code> if a
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Python exception is raised.</dt>
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</dl>
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<h3><a name="objattribute_policies-spec"></a>Class
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<code>objattribute_policies</code></h3>
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<p>The policies which are used for proxies representing an attribute
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access to a mutable <code>object</code> when the attribute name is
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given as a <code>const&nbsp;object</code>.</p>
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<h4><a name="objattribute_policies-spec-synopsis"></a>Class
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<code>objattribute_policies</code> synopsis</h4>
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<pre>
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namespace boost { namespace python { namespace api
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{
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struct objattribute_policies : const_objattribute_policies
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{
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static object const&amp; set(object const&amp; target, object const& key, object const&amp; value);
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static void del(object const&amp;target, object const& key);
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};
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}}}
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</pre>
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<h4><a name="objattribute_policies-spec-statics"></a>Class
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<code>objattribute_policies</code> static functions</h4>
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<pre>
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static object const&amp; set(object const&amp; target, object const& key, object const&amp; value);
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> <code>key</code> is an <code>object</code>
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holding a string.</dt>
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<dt><b>Effects:</b> sets the attribute of <code>target</code> named by
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<code>key</code> to <code>value</code>.</dt>
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<dt><b>Throws:</b> <code><a href=
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"errors.html#error_already_set-spec">error_already_set</a></code> if a
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Python exception is raised.</dt>
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</dl>
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<pre>
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static void del(object const&amp;target, object const& key);
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> <code>key</code> is an <code>object</code>
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holding a string.</dt>
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<dt><b>Effects:</b> deletes the attribute of <code>target</code> named
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by <code>key</code>.</dt>
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<dt><b>Throws:</b> <code><a href=
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"errors.html#error_already_set-spec">error_already_set</a></code> if a
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Python exception is raised.</dt>
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</dl>
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<!-- end -->
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<!-- begin -->
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<h3><a name="const_item_policies-spec"></a>Class
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<code>const_item_policies</code></h3>
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//
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proxy&lt;const_object_attribute&gt; attr(char const*) const;
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proxy&lt;object_attribute&gt; attr(char const*);
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proxy&lt;const_object_objattribute&gt; attr(object const&) const;
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proxy&lt;object_objattribute&gt; attr(object const&);
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// item access
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//
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<code>name</code> as its key.</dt>
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</dl>
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<pre>
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proxy&lt;const_object_objattribute&gt; attr(const object& name) const;
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proxy&lt;object_objattribute&gt; attr(const object& name);
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</pre>
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<dl class="function-semantics">
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<dt><b>Requires:</b> name is a <code>object</code> holding a string.</dt>
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<dt><b>Effects:</b> accesses the named attribute of
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<code>*this</code>.</dt>
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<dt><b>Returns:</b> a proxy object which binds
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<code>object(*static_cast&lt;U*&gt;(this))</code> as its target, and
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<code>name</code> as its key.</dt>
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</dl>
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<pre>
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template &lt;class T&gt;
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proxy&lt;const_object_item&gt; operator[](T const&amp; key) const;
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template &lt;class T&gt;
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</pre>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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13 January, 2006
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27 May, 2008
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<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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</p>
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<p><i>&copy; Copyright <a href=
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"http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2006.</i></p>
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"http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2008.</i></p>
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</body>
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</html>

‎include/boost/python/object_attributes.hpp‎

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{
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typedef char const* key_type;
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static object get(object const& target, char const* key);
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static object get(object const& target, object const& key);
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};
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struct const_objattribute_policies
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{
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typedef object const key_type;
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static object get(object const& target, object const& key);
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};
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struct objattribute_policies : const_objattribute_policies
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{
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static object const& set(object const& target, object const& key, object const& value);
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static void del(object const&target, object const& key);
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};
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//
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// implementation
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template <class U>
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inline object_objattribute object_operators<U>::attr(object const& name)
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{
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object_cref2 x = *static_cast<U*>(this);
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return object_objattribute(x, name);
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}
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template <class U>
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inline const_object_objattribute object_operators<U>::attr(object const& name) const
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{
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object_cref2 x = *static_cast<U const*>(this);
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return const_object_objattribute(x, name);
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}
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inline object const_objattribute_policies::get(object const& target, object const& key)
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{
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return python::getattr(target, key);
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}
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inline object const& objattribute_policies::set(
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python::setattr(target, key, value);
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object const& target
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python::delattr(target, key);
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}
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#endif // OBJECT_ATTRIBUTES_DWA2002615_HPP

‎include/boost/python/object_core.hpp‎

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struct const_objattribute_policies;
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typedef proxy<objattribute_policies> object_objattribute;
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const_object_objattribute attr(object const&) const;
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object_objattribute attr(object const&);
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// item access
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//

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