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<!-- Generated by the Spirit (http://spirit.sf.net) QuickDoc -->
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<title>Class Data Members</title>
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<font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Class Data Members</b></font>
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<p>
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Data members may also be exposed to Python so that they can be
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accessed as attributes of the corresponding Python class. Each data
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member that we wish to be exposed may be regarded as <b>read-only</b> or
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<b>read-write</b>. Consider this class <tt>Var</tt>:</p>
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<code><pre>
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<span class=keyword>struct </span><span class=identifier>Var
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</span><span class=special>{
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</span><span class=identifier>Var</span><span class=special>(</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>name</span><span class=special>) : </span><span class=identifier>name</span><span class=special>(</span><span class=identifier>name</span><span class=special>), </span><span class=identifier>value</span><span class=special>() {}
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</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=keyword>const </span><span class=identifier>name</span><span class=special>;
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</span><span class=keyword>float </span><span class=identifier>value</span><span class=special>;
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};
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</span></pre></code>
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<p>
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Our C++ <tt>Var</tt> class and its data members can be exposed to Python:</p>
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<code><pre>
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<span class=identifier>class_</span><span class=special><</span><span class=identifier>Var</span><span class=special>>(</span><span class=string>"Var"</span><span class=special>, </span><span class=identifier>init</span><span class=special><</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>>())
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.</span><span class=identifier>def_readonly</span><span class=special>(</span><span class=string>"name"</span><span class=special>, &</span><span class=identifier>Var</span><span class=special>::</span><span class=identifier>name</span><span class=special>)
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.</span><span class=identifier>def_readwrite</span><span class=special>(</span><span class=string>"value"</span><span class=special>, &</span><span class=identifier>Var</span><span class=special>::</span><span class=identifier>value</span><span class=special>);
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</span></pre></code>
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<p>
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Then, in Python, assuming we have placed our Var class inside the namespace
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hello as we did before:</p>
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<code><pre>
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<span class=special>>>> </span><span class=identifier>x </span><span class=special>= </span><span class=identifier>hello</span><span class=special>.</span><span class=identifier>Var</span><span class=special>(</span><span class=literal>'pi'</span><span class=special>)
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>>> </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>value </span><span class=special>= </span><span class=number>3.14
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</span><span class=special>>>> </span><span class=identifier>print </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>name</span><span class=special>, </span><span class=literal>'is around'</span><span class=special>, </span><span class=identifier>x</span><span class=special>.</span><span class=identifier>value
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</span><span class=identifier>pi </span><span class=identifier>is </span><span class=identifier>around </span><span class=number>3.14
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</span></pre></code>
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<p>
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Note that <tt>name</tt> is exposed as <b>read-only</b> while <tt>value</tt> is exposed
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as <b>read-write</b>.</p>
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<code><pre>
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>>> x.name = 'e' # can't change name
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Traceback (most recent call last):
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File "<stdin>", line 1, in ?
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AttributeError: can't set attribute
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</pre></code><table border="0">
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<br>
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<hr size="1"><p class="copyright">Copyright © 2002-2003 David Abrahams<br>Copyright © 2002-2003 Joel de Guzman<br><br>
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<font size="2">Permission to copy, use, modify, sell and distribute this document
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is granted provided this copyright notice appears in all copies. This document
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is provided "as is" without express or implied warranty, and with
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no claim as to its suitability for any purpose. </font> </p>
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