<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <!-- Copyright David Abrahams 2006. Distributed under the Boost --> <!-- Software License, Version 1.0. (See accompanying --> <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> <html> <head> <meta name="generator" content= "HTML Tidy for Cygwin (vers 1st September 2004), see www.w3.org"> <meta http-equiv="Content-Type" content="text/html; charset=iso-latin-1-dos"> <link rel="stylesheet" type="text/css" href="../boost.css"> <title>Boost.Python - <boost/python/class.hpp>, <boost/python/class_fwd.hpp></title> </head> <body link="#0000FF" vlink="#800080"> <table border="0" cellpadding="7" cellspacing="0" width="100%" summary= "header"> <tr> <td valign="top" width="300"> <h3><a href="../../../../index.htm"><img height="86" width="277" alt= "C++ Boost" src="../../../../boost.png" border="0"></a></h3> </td> <td valign="top"> <h1 align="center"><a href="../index.html">Boost.Python</a></h1> <h2 align="center">Headers <boost/python/class.hpp>, <boost/python/class_fwd.hpp></h2> </td> </tr> </table> <hr> <h2>Contents</h2> <dl class="page-index"> <dt><a href="#introduction">Introduction</a></dt> <dt><a href="#classes">Classes</a></dt> <dd> <dl class="page-index"> <dt><a href="#class_-spec">Class template <code>class_</code></a></dt> <dd> <dl class="page-index"> <dt><a href="#class_-spec-synopsis">Class <code>class_</code> synopsis</a></dt> <dt><a href="#class_-spec-ctors">Class <code>class_</code> constructors</a></dt> <dt><a href="#class_-spec-modifiers">Class <code>class_</code> modifier functions</a></dt> </dl> </dd> <dt><a href="#bases-spec">Class template <code>bases</code></a></dt> <dd> <dl class="page-index"> <dt><a href="#bases-spec-synopsis">Class template <code>bases</code> synopsis</a></dt> </dl> </dd> </dl> </dd> <dt><a href="#examples">Example(s)</a></dt> </dl> <hr> <h2><a name="introduction" id="introduction"></a>Introduction</h2> <p><code><boost/python/class.hpp></code> defines the interface through which users expose their C++ classes to Python. It declares the <code>class_</code> class template, which is parameterized on the class type being exposed. It also exposes the <code>init</code>, <code>optional</code> and <code>bases</code> utility class templates, which are used in conjunction with <code>class_</code>.</p> <p><code><boost/python/class_fwd.hpp></code> contains a forward declaration of the <code>class_</code> class template.</p> <h2><a name="classes" id="classes"></a>Classes</h2> <h3><a name="class_-spec" id="class_-spec"></a>Class template <code>class_<T, <font color="#007F00">Bases, HeldType, NonCopyable</font>></code></h3> <p>Creates a Python class associated with the C++ type passed as its first parameter. Although it has four template parameters, only the first one is required. The three optional arguments can actually be supplied <font color="#007F00"><b>in any order</b></font>; Boost.Python determines the role of the argument from its type.<br> <br></p> <table border="1" summary="class_ template parameters"> <tr> <th>Template Parameter</th> <th>Requirements</th> <th>Semantics</th> <th>Default</th> </tr> <tr> <td><code>T</code></td> <td>A class type.</td> <td>The class being wrapped</td> </tr> <tr> <td><code><font color="#007F00">Bases</font></code></td> <td>A specialization of <a href= "#bases-spec"><code>bases<</code>...<code>></code></a> which specifies previously-exposed C++ base classes of <code>T</code><a href= "#footnote_1">[1]</a>.</td> <td>Registers <code>from_python</code> conversions from wrapped <code>T</code> instances to each of its exposed direct and indirect bases. For each polymorphic base <code>B</code>, registers conversions from indirectly-held wrapped <code>B</code> instances to <code>T</code>.</td> <td><code><a href="#bases-spec">bases<></a></code></td> </tr> <tr> <td><code><font color="#007F00">HeldType</font></code></td> <td>Must be <code>T</code>, a class derived from <code>T</code>, or a <a href="Dereferenceable.html">Dereferenceable</a> type for which <code><a href= "pointee.html#pointee-spec">pointee</a><HeldType>::type</code> is <code>T</code> or a class derived from <code>T</code>.</td> <td>Specifies the type that is actually embedded in a Python object wrapping a <code>T</code> instance when <code>T</code>'s constructor is called or when a <code>T</code> or <code>T*</code> is converted to Python without the use of <a href= "http://www.boost.org/libs/python/doc/v2/callbacks.html#argument_handling"> <code>ptr</code></a>, <a href= "http://www.boost.org/libs/python/doc/v2/callbacks.html#argument_handling"> <code>ref</code></a>, or <a href="CallPolicies.html">Call Policies</a> such as <code><a href= "return_internal_reference.html">return_internal_reference</a></code>. More details <a href="#HeldType">below</a>.</td> <td><code>T</code></td> </tr> <tr> <td><code><font color="#007F00">NonCopyable</font></code></td> <td>If supplied, must be <a href= "../../../utility/utility.htm#Class_noncopyable">boost::noncopyable</a>.</td> <td>Suppresses automatic registration of <code>to_python</code> conversions which copy <code>T</code> instances. Required when <code>T</code> has no publicly-accessible copy constructor.</td> <td>An unspecified type other than <code>boost::noncopyable</code>.</td> </tr> </table> <h4><a name="HeldType" id="HeldType">HeldType Semantics</a></h4> <ol> <li>If <code>HeldType</code> is derived from T, its exposed constructor(s) must accept an initial <code>PyObject*</code> argument which refers back to the Python object that contains the <code>HeldType</code> instance, as shown in <a href= "call_method.html#examples">this example</a>. This argument is not included in the <em><a href= "init.html#init-expressions">init-expression</a></em> passed to <a href= "#class_-spec-modifiers"><code>def(init_expr)</code></a>, below, nor is it passed explicitly by users when Python instances of <code>T</code> are created. This idiom allows C++ virtual functions which will be overridden in Python to access the Python object so the Python method can be invoked. Boost.Python automatically registers additional converters which allow wrapped instances of <code>T</code> to be passed to wrapped C++ functions expecting <code>HeldType</code> arguments.</li> <li>Because Boost.Python will always allow wrapped instances of <code>T</code> to be passed in place of <code>HeldType</code> arguments, specifying a smart pointer for <code>HeldType</code> allows users to pass Python <code>T</code> instances where a smart pointer-to-<code>T</code> is expected. Smart pointers such as <code>std::auto_ptr<></code> or <code><a href= "../../../smart_ptr/shared_ptr.htm">boost::shared_ptr<></a></code> which contain a nested type <code>element_type</code> designating the referent type are automatically supported; additional smart pointer types can be supported by specializing <a href= "pointee.html#pointee-spec">pointee<HeldType></a>.</li> <li>As in case 1 above, when <code>HeldType</code> is a smart pointer to a class derived from <code>T</code>, the initial <code>PyObject*</code> argument must be supplied by all of <code>HeldType</code>'s exposed constructors.</li> <li>Except in cases 1 and 3, users may optionally specify that T itself gets initialized with a similar initial <code>PyObject*</code> argument by specializing <a href= "has_back_reference.html#has_back_reference-spec">has_back_reference<T></a>.</li> </ol> <h4><a name="class_-spec-synopsis" id="class_-spec-synopsis"></a>Class template <code>class_</code> synopsis</h4> <pre> namespace boost { namespace python { template <class T <font color="#007F00"> , class Bases = bases<> , class HeldType = T , class NonCopyable = <i>unspecified</i> > </font> class class_ : public <a href="object.html#object-spec">object</a> { // Constructors with default __init__ class_(char const* name); class_(char const* name, char const* docstring); // Constructors, specifying non-default __init__ template <class Init> class_(char const* name, Init); template <class Init> class_(char const* name, char const* docstring, Init); // Exposing additional __init__ functions template <class Init> class_& def(Init); // defining methods template <class F> class_& def(char const* name, F f); template <class Fn, class A1> class_& def(char const* name, Fn fn, A1 const&); template <class Fn, class A1, class A2> class_& def(char const* name, Fn fn, A1 const&, A2 const&); template <class Fn, class A1, class A2, class A3> class_& def(char const* name, Fn fn, A1 const&, A2 const&, A3 const&); // declaring method as static class_& staticmethod(char const* name); // exposing operators template <<i>unspecified</i>> class_& def(<a href= "operators.html#operator_-spec">detail::operator_</a><unspecified>); // Raw attribute modification template <class U> class_& setattr(char const* name, U const&); // exposing data members template <class D> class_& def_readonly(char const* name, D T::*pm); template <class D> class_& def_readwrite(char const* name, D T::*pm); // exposing static data members template <class D> class_& def_readonly(char const* name, D const& d); template <class D> class_& def_readwrite(char const* name, D& d); // property creation template <class Get> void add_property(char const* name, Get const& fget, char const* doc=0); template <class Get, class Set> void add_property( char const* name, Get const& fget, Set const& fset, char const* doc=0); template <class Get> void add_static_property(char const* name, Get const& fget); template <class Get, class Set> void add_static_property(char const* name, Get const& fget, Set const& fset); // pickle support template <typename PickleSuite> self& def_pickle(PickleSuite const&); self& enable_pickling(); }; }} </pre> <h4><a name="class_-spec-ctors" id="class_-spec-ctors"></a>Class template <code>class_</code> constructors</h4> <pre> class_(char const* name); class_(char const* name, char const* docstring); template <class Init> class_(char const* name, Init init_spec); template <class Init> class_(char const* name, char const* docstring, Init init_spec); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>name</code> is an <a href= "definitions.html#ntbs">ntbs</a> which conforms to Python's <a href= "http://www.python.org/doc/current/ref/identifiers.html">identifier naming rules</a>. If <code>docstring</code> is supplied, it must be an <a href="definitions.html#ntbs">ntbs</a>. If <code>init_spec</code> is supplied, it must be either the special enumeration constant <code>no_init</code> or an <a href= "init.html#init-expressions">init-expression</a> compatible with <code>T</code>.</dt> <dt><b>Effects:</b> Constructs a <code>class_</code> object holding a Boost.Python extension class named <code>name</code>. The <code>name</code>d attribute of the <a href= "scope.html#introduction">current scope</a> is bound to the new extension class.</dt> <dd> <ul> <li>If supplied, the value of <code>docstring</code> is bound to the <code>__doc__</code> attribute of the extension class.</li> <li>If <code>init_spec</code> is <code>no_init</code>, a special <code>__init__</code> function is generated which always raises a Python exception. Otherwise, <code>this->def(init_spec)</code> is called.</li> <li>If <code>init_spec</code> is not supplied, <code>this->def(init<>())</code> is called.</li> </ul> </dd> <dt><b>Rationale:</b>Allowing the user to specify constructor arguments in the <code>class_<></code> constructor helps her to avoid the common run-time errors which result from invoking wrapped member functions without having exposed an <code>__init__</code> function which creates the requisite <code>T</code> instance. Types which are not default-constructible will cause a compile-time error unless <code>Init</code> is supplied. The user must always supply <code>name</code> as there is currently no portable method to derive the text of the class name from its type.</dt> </dl> <h4><a name="class_-spec-modifiers" id="class_-spec-modifiers"></a>Class template <code>class_</code> modifier functions</h4> <pre> template <class Init> class_& def(Init init_expr); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>init_expr</code> is the result of an <a href= "init.html#init-expressions">init-expression</a> compatible with <code>T</code>.</dt> <dt><b>Effects:</b> For each <a href="init.html#init-expressions">valid prefix</a> <em>P</em> of <code>Init</code>, adds an <code>__init__(</code>...<code>)</code> function overload to the extension class accepting <em>P</em> as arguments. Each overload generated constructs an object of <code>HeldType</code> according to the semantics described <a href="#HeldType">above</a>, using a copy of <code>init_expr</code>'s <a href="CallPolicies.html">call policies</a>. If the longest <a href="init.html#init-expressions">valid prefix</a> of <code>Init</code> contains <em>N</em> types and <code>init_expr</code> holds <em>M</em> keywords, an initial sequence of the keywords are used for all but the first <em>N</em> - <em>M</em> arguments of each overload.</dt> <dt><b>Returns:</b> <code>*this</code></dt> <dt><b>Rationale:</b> Allows users to easily expose a class' constructor to Python.</dt> </dl><br> <pre> template <class F> class_& def(char const* name, Fn fn); template <class Fn, class A1> class_& def(char const* name, Fn fn, A1 const& a1); template <class Fn, class A1, class A2> class_& def(char const* name, Fn fn, A1 const& a1, A2 const& a2); template <class Fn, class A1, class A2, class A3> class_& def(char const* name, Fn fn, A1 const& a1, A2 const& a2, A3 const& a3); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>name</code> is an <a href= "definitions.html#ntbs">ntbs</a> which conforms to Python's <a href= "http://www.python.org/doc/current/ref/identifiers.html">identifier naming rules</a>.</dt> <dd> <ul> <li>If <code>a1</code> is the result of an <a href= "overloads.html#overload-dispatch-expression"><em>overload-dispatch-expression</em></a>, only the second form is allowed and fn must be a pointer to function or pointer to member function whose <a href="definitions.html#arity"> arity</a> is the same as A1's <a href= "overloads.html#overload-dispatch-expression"><em>maximum arity</em></a>. <dl> <dt><b>Effects:</b> For each prefix <em>P</em> of <code>Fn</code>'s sequence of argument types, beginning with the one whose length is <code>A1</code>'s <a href= "overloads.html#overload-dispatch-expression"><em>minimum arity</em></a>, adds a <code><em>name</em>(</code>...<code>)</code> method overload to the extension class. Each overload generated invokes <code>a1</code>'s call-expression with <em>P</em>, using a copy of <code>a1</code>'s <a href="CallPolicies.html">call policies</a>. If the longest valid prefix of <code>A1</code> contains <em>N</em> types and <code>a1</code> holds <em>M</em> keywords, an initial sequence of the keywords are used for all but the first <em>N</em> - <em>M</em> arguments of each overload.<br></dt> </dl> </li> <li>Otherwise, a single method overload is built around fn, which must not be null: <ul> <li>If fn is a function pointer, its first argument must be of the form <code>U</code>, <code>U <em>cv</em>&</code>, <code>U <em>cv</em>*</code>, or <code>U <em>cv</em>* const&</code>, where <code>T*</code> is convertible to <code>U*</code>, and <code>a1</code>-<code>a3</code>, if supplied, may be selected in any order from the table below.</li> <li>Otherwise, if fn is a member function pointer, its target must be <code>T</code> or one of its public base classes, and <code>a1</code>-<code>a3</code>, if supplied, may be selected in any order from the table below.</li> <li>Otherwise, <code>Fn</code> must be [derived from] <code><a href="object.html#object-spec">object</a></code>, and <code>a1-a2</code>, if supplied, may be selcted in any order from the first two rows of the table below. To be useful, <code>fn</code> should be <a href= "http://www.python.org/doc/current/lib/built-in-funcs.html#l2h-6"> callable</a>.</li> </ul> <table border="1" summary="def() optional arguments"> <tr> <th>Memnonic Name</th> <th>Requirements/Type properties</th> <th>Effects</th> </tr> <tr> <td>docstring</td> <td>Any <a href="definitions.html#ntbs">ntbs</a>.</td> <td>Value will be bound to the <code>__doc__</code> attribute of the resulting method overload. If an earlier overload supplied a docstring, two newline characters and the new docstring are appended to it.</td> </tr> <tr> <td>policies</td> <td>A model of <a href= "CallPolicies.html">CallPolicies</a></td> <td>A copy will be used as the call policies of the resulting method overload.</td> </tr> <tr> <td>keywords</td> <td>The result of a <a href= "args.html#keyword-expression"><em>keyword-expression</em></a> specifying no more arguments than the <a href= "definitions.html#arity">arity</a> of <code>fn</code>.</td> <td>A copy will be used as the call policies of the resulting method overload.</td> </tr> </table> </li> </ul> </dd> <dt><b>Returns:</b> <code>*this</code></dt> </dl> <pre> class_& staticmethod(char const* name); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>name</code> is an <a href= "definitions.html#ntbs">ntbs</a> which conforms to Python's <a href= "http://www.python.org/doc/current/ref/identifiers.html">identifier naming rules</a>, and corresponds to a method whose overloads have all been defined.</dt> <dt><b>Effects:</b> Replaces the existing named attribute <i>x</i> with the result of invoking <code>staticmethod(</code><i>x</i><code>)</code> in Python. Specifies that the corresponding method is static and therefore no object instance will be passed to it. This is equivalent to the Python statement:</dt> <dd> <pre> setattr(self, name, staticmethod(getattr(self, name))) </pre> </dd> <dt><b>Note:</b> Attempting to invoke <code>def(name,...)</code> after invoking <code>staticmethod(name)</code> will <a href= "definitions.html#raise">raise</a> a RuntimeError.</dt> <dt><b>Returns:</b> <code>*this</code></dt> </dl><br> <pre> template <<i>unspecified</i>> class_& def(<a href= "operators.html#operator_-spec">detail::operator_</a><unspecified>); </pre> <dl class="function-semantics"> <dt><b>Effects:</b> Adds a Python <a href= "http://www.python.org/doc/ref/specialnames.html">special method</a> as described <a href="operators.html">here</a>.</dt> <dt><b>Returns:</b> <code>*this</code></dt> </dl> <pre> template <class U> class_& setattr(char const* name, U const& u); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>name</code> is an <a href= "definitions.html#ntbs">ntbs</a> which conforms to Python's <a href= "http://www.python.org/doc/current/ref/identifiers.html">identifier naming rules</a>.</dt> <dt><b>Effects:</b> Converts u to Python and adds it to the attribute dictionary of the extension class:</dt> <dd> <blockquote> <code><a href= "http://www.python.org/doc/current/api/object.html#l2h-166">PyObject_SetAttrString</a>(this->ptr(), name, <a href= "object.html#object-spec-ctors">object</a>(u).ptr());</code> </blockquote> </dd> <dt><b>Returns:</b> <code>*this</code></dt> </dl><br> <pre> template <class Get> void add_property(char const* name, Get const& fget, char const* doc=0); template <class Get, class Set> void add_property( char const* name, Get const& fget, Set const& fset, char const* doc=0); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>name</code> is an <a href= "definitions.html#ntbs">ntbs</a> which conform to Python's <a href= "http://www.python.org/doc/current/ref/identifiers.html">identifier naming rules</a>.</dt> <dt><b>Effects:</b> Creates a new Python <a href= "http://www.python.org/2.2.2/descrintro.html#property"><code>property</code></a> class instance, passing <code><a href= "object.html#object-spec-ctors">object</a>(fget)</code> (and <code><a href="object.html#object-spec-ctors">object</a>(fset)</code> in the second form) with an (optional) docstring <code>doc</code> to its constructor, then adds that property to the Python class object under construction with the given attribute <code>name</code>.</dt> <dt><b>Returns:</b> <code>*this</code></dt> <dt><b>Rationale:</b> Allows users to easily expose functions that can be invoked from Python with attribute access syntax.</dt> </dl><br> <pre> template <class Get> void add_static_property(char const* name, Get const& fget); template <class Get, class Set> void add_static_property(char const* name, Get const& fget, Set const& fset); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>name</code> is an <a href= "definitions.html#ntbs">ntbs</a> which conforms to Python's <a href= "http://www.python.org/doc/current/ref/identifiers.html">identifier naming rules</a>.</dt> <dt><b>Effects:</b> Creates a Boost.Python.StaticProperty object, passing <code><a href="object.html#object-spec-ctors">object</a>(fget)</code> (and <code><a href= "object.html#object-spec-ctors">object</a>(fset)</code> in the second form) to its constructor, then adds that property to the Python class under construction with the given attribute <code>name</code>. StaticProperty is a special subclass of Python's <a href= "http://www.python.org/2.2.2/descrintro.html#property"><code>property</code></a> class which can be called without an initial <code>self</code> argument.</dt> <dt><b>Returns:</b> <code>*this</code></dt> <dt><b>Rationale:</b> Allows users to easily expose functions that can be invoked from Python with static attribute access syntax.</dt> </dl><br> <pre> template <class D> class_& def_readonly(char const* name, D T::*pm, char const* doc=0); template <class D> class_& def_readonly(char const* name, D const& d); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> <code>name</code> is an <a href= "definitions.html#ntbs">ntbs</a> which conforms to Python's <a href= "http://www.python.org/doc/current/ref/identifiers.html">identifier naming rules</a>. <code>doc</code> is also an ntbs.</dt> <dt><b>Effects:</b></dt> <dd> <pre> this->add_property(name, <a href= "data_members.html#make_getter-spec">make_getter</a>(pm), doc); </pre>and <pre> this->add_static_property(name, <a href= "data_members.html#make_getter-spec">make_getter</a>(d)); </pre>respectively.<br> <br> </dd> <dt><b>Returns:</b> <code>*this</code></dt> <dt><b>Rationale:</b> Allows users to easily expose a class' data member or free variable such that it can be inspected from Python with a natural syntax.</dt> </dl> <pre> template <class D> class_& def_readwrite(char const* name, D T::*pm, char const* doc=0); template <class D> class_& def_readwrite(char const* name, D& d); </pre> <dl class="function-semantics"> <dt><b>Effects:</b></dt> <dd> <pre> this->add_property(name, <a href= "data_members.html#make_getter-spec">make_getter</a>(pm), <a href= "data_members.html#make_setter-spec">make_setter</a>(pm), doc); </pre>and <pre> this->add_static_property(name, <a href= "data_members.html#make_getter-spec">make_getter</a>(d), <a href= "data_members.html#make_setter-spec">make_setter</a>(d)); </pre>respectively.<br> <br> </dd> <dt><b>Returns:</b> <code>*this</code></dt> <dt><b>Rationale:</b> Allows users to easily expose a class' data or free variable member such that it can be inspected and set from Python with a natural syntax.</dt> </dl> <pre> template <typename PickleSuite> class_& def_pickle(PickleSuite const&); </pre> <dl class="function-semantics"> <dt><b>Requires:</b> PickleSuite must be publically derived from <a href= "pickle.html"><code>pickle_suite</code></a>.</dt> <dt><b>Effects:</b> Defines a legal combination of the special attributes and methods: <code>__getinitargs__</code>, <code>__getstate__</code>, <code>__setstate__</code>, <code>__getstate_manages_dict__</code>, <code>__safe_for_unpickling__</code>, <code>__reduce__</code></dt> <dt><b>Returns:</b> <code>*this</code></dt> <dt><b>Rationale:</b> Provides an <a href="pickle.html">easy to use high-level interface</a> for establishing complete pickle support for the wrapped class. The user is protected by compile-time consistency checks.</dt> </dl><br> <pre> class_& enable_pickling(); </pre> <dl class="function-semantics"> <dt><b>Effects:</b> Defines the <code>__reduce__</code> method and the <code>__safe_for_unpickling__</code> attribute.</dt> <dt><b>Returns:</b> <code>*this</code></dt> <dt><b>Rationale:</b> Light-weight alternative to <code>def_pickle()</code>. Enables implementation of <a href= "pickle.html">pickle support</a> from Python.</dt> </dl><br> <h3><a name="bases-spec" id="bases-spec"></a>Class template <code>bases<T1, T2,</code>...<code>TN></code></h3> <p>An <a href="../../../mpl/doc/refmanual/forward-sequence.html">MPL sequence</a> which can be used in <code>class_<</code>...<code>></code> instantiations indicate a list of base classes.</p> <h4><a name="bases-spec-synopsis" id="bases-spec-synopsis"></a>Class template <code>bases</code> synopsis</h4> <pre> namespace boost { namespace python { template <T1 = <i>unspecified</i>,...T<i>n</i> = <i>unspecified</i>> struct bases {}; }} </pre> <h2><a name="examples" id="examples"></a>Example(s)</h2> <p>Given a C++ class declaration:</p> <pre> class Foo : public Bar, public Baz { public: Foo(int x, char const* y); Foo(double); std::string const& name() { return m_name; } void name(char const*); double value; // public data private: ... }; </pre>A corresponding Boost.Python extension class can be created with: <pre> using namespace boost::python; class_<Foo,bases<Bar,Baz> >("Foo", "This is Foo's docstring." "It describes our Foo extension class", init<int,char const*>(args("x","y"), "__init__ docstring") ) .def(init<double>()) .def("get_name", &Foo::get_name, return_internal_reference<>()) .def("set_name", &Foo::set_name) .def_readwrite("value", &Foo::value) ; </pre> <hr> <a name="footnote_1" id="footnote_1">[1]</a> By "previously-exposed" we mean that the for each <code>B</code> in <code>bases</code>, an instance of <code>class_<B<font color="#007F00">, ...</font>></code> must have already been constructed. <pre> class_<Base>("Base"); class_<Derived, bases<Base> >("Derived"); </pre>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> 1 November, 2005 <!--webbot bot="Timestamp" endspan i-checksum="39359" --> <p><i>© Copyright <a href="http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a> 2002.</i></p> </body> </html>