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'Version_1_21_0'. [SVN r9525]
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nobody
@@ -1,7 +1,7 @@
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN"
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"http://www.w3.org/TR/REC-html40/strict.dtd">
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<title>
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A Simple Example Using py_cpp
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A Simple Example
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</title>
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<div>
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<h1>
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@@ -9,7 +9,7 @@
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"c++boost.gif (8819 bytes)">
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</h1>
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<h1>
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A Simple Example Using py_cpp
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A Simple Example
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</h1>
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<p>
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Suppose we have the following C++ API which we want to expose in
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@@ -18,104 +18,57 @@
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<pre>
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#include <string>
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namespace hello {
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class world
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{
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public:
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world(int);
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~world();
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std::string get() const { return "hi, world"; }
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...
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};
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std::size_t length(const world& x) { return std::strlen(x.get()); }
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namespace { // Avoid cluttering the global namespace.
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// A couple of simple C++ functions that we want to expose to Python.
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std::string greet() { return "hello, world"; }
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int square(int number) { return number * number; }
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}
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</pre>
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</blockquote>
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<p>
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Here is the C++ code for a python module called <code>hello</code>
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which exposes the API using py_cpp:
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Here is the C++ code for a python module called <tt>getting_started1</tt>
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which exposes the API.
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<blockquote>
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<pre>
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#include <boost/python/class_builder.hpp>
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// Python requires an exported function called init<module-name> in every
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// extension module. This is where we build the module contents.
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extern "C"
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#ifdef _WIN32
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__declspec(dllexport)
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#endif
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void inithello()
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#include <boost/python/class_builder.hpp>
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namespace python = boost::python;
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BOOST_PYTHON_MODULE_INIT(getting_started1)
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{
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try
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{
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// create an object representing this extension module
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boost::python::module_builder hello("hello");
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// Create the Python type object for our extension class
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boost::python::class_builder<hello::world> world_class(hello, "world");
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// Add the __init__ function
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world_class.def(boost::python::constructor<int>());
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// Add a regular member function
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world_class.def(&hello::world::get, "get");
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// Add a regular function to the module
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hello.def(hello::length, "length");
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}
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catch(...)
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{
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boost::python::handle_exception(); // Deal with the exception for Python
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}
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try
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{
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// Create an object representing this extension module.
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python::module_builder this_module("getting_started1");
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// Add regular functions to the module.
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this_module.def(greet, "greet");
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this_module.def(square, "square");
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}
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catch(...)
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{
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python::handle_exception(); // Deal with the exception for Python
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}
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}
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// Win32 DLL boilerplate
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#if defined(_WIN32)
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#include <windows.h>
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extern "C" BOOL WINAPI DllMain(HINSTANCE, DWORD, LPVOID)
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{
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return 1;
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}
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#endif // _WIN32
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</pre>
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</blockquote>
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<p>
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That's it! If we build this shared library and put it on our <code>
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PYTHONPATH</code> we can now access our C++ class and function from
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PYTHONPATH</code> we can now access our C++ functions from
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Python.
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<blockquote>
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<pre>
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>>> import hello
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>>> hi_world = hello.world(3)
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>>> hi_world.get()
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'hi, world'
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>>> hello.length(hi_world)
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9
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>>> import getting_started1
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>>> print getting_started1.greet()
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hello, world
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>>> number = 11
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>>> print number, '*', number, '=', getting_started1.square(number)
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11 * 11 = 121
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</pre>
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</blockquote>
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<p>
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We can even make a subclass of <code>hello.world</code>:
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<blockquote>
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<pre>
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>>> class my_subclass(hello.world):
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... def get(self):
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... return 'hello, world'
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...
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>>> y = my_subclass(4)
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>>> y.get()
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'hello, world'
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</pre>
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</blockquote>
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<p>
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Pretty cool! You can't do that with an ordinary Python extension type!
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<blockquote>
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<pre>
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>>> hello.length(y)
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9
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</pre>
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</blockquote>
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<p>
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Of course, you may now have a slightly empty feeling in the pit of
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your little pythonic stomach. Perhaps you feel your subclass deserves
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to have a <code>length()</code> of <code>12</code>? If so, <a href=
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"overriding.html">read on</a>...
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<p>
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Previous: <a href="comparisons.html">Comparisons with other systems</a> Next: <a href="overriding.html">Overridable virtual functions</a> Up:
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Next: <a href="exporting_classes.html">Exporting Classes</a>
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Previous: <a href="comparisons.html">Comparisons with other systems</a> Up:
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<a href="index.html">Top</a>
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<p>
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© Copyright David Abrahams 2000. Permission to copy, use, modify,
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@@ -124,6 +77,6 @@ extern "C" BOOL WINAPI DllMain(HINSTANCE, DWORD, LPVOID)
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express or implied warranty, and with no claim as to its suitability
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for any purpose.
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<p>
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Updated: Nov 26, 2000
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Updated: Mar 6, 2000
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</div>
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