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Boost.PythonHeader <call_method.hpp> |
<boost/python/call_method.hpp> defines the call_method family of overloaded
function templates, used to invoke callable attributes of Python objects
from C++.
template <class R, class A1, class A2, ... class An> R call_method(PyObject* self, char const* method, A1 const&, A2 const&, ... An const&)
R is a pointer type, reference type,
or a complete type with an accessible copy constructorself.method(a1, a2, ...an) in
Python, where a1...an are the
arguments to call_method(), converted to Python objects.
For a complete semantic description, see this
page.R.call_method is critical to
implementing C++ virtual functions which are overridable in Python, as
shown by the example below.call_method in
wrapping a class with a virtual function that can be overridden in
Python:
#include <boost/python/module.hpp>
#include <boost/python/class.hpp>
#include <boost/utility.hpp>
#include <cstring>
// class to be wrapped
class Base
{
public:
virtual char const* class_name() const { return "Base"; }
virtual ~Base();
};
bool is_base(Base* b)
{
return !std::strcmp(b->class_name(), "Base");
}
// Wrapper code begins here
using namespace boost::python;
// Callback class
class Base_callback : public Base
{
public:
Base_callback(PyObject* self) : m_self(self) {}
char const* class_name() const { return call_method<char const*>(m_self, "class_name"); }
char const* Base_name() const { return Base::class_name(); }
private:
PyObject* const m_self;
};
using namespace boost::python;
BOOST_PYTHON_MODULE(my_module)
{
def("is_base", is_base);
class_<Base,Base_callback, noncopyable>("Base")
.def("class_name", &Base_callback::Base_name)
;
}
>>> from my_module import * >>> class Derived(Base): ... def __init__(self): ... Base.__init__(self) ... def class_name(self): ... return self.__class__.__name__ ... >>> is_base(Base()) # calls the class_name() method from C++ 1 >>> is_base(Derived()) 0
Revised 13 November, 2002
© Copyright Dave Abrahams 2002.