...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
to_python_converter
to_python_converter
synopsisto_python_converter
constructorto_python_converter
registers a conversion from objects of a
given C++ type into a Python object.
to_python_converter
to_python_converter
adds a wrapper around a static member
function of its second template parameter, handling low-level details
such as insertion into the converter registry.
Parameter | Requirements | Description |
---|---|---|
T |
The C++ type of the source object in the conversion | |
Conversion |
PyObject* p = Conversion::convert(x) ,if p == 0 , PyErr_Occurred() != 0 . |
A class type whose static member function convert
does the real work of the conversion. |
bool has_get_pytype = false |
PyTypeObject const * p = Conversion::get_pytype() . |
Optional member - if Conversion has get_pytype member supply
true for this parameters.
If present get_pytype is used to document the return type
of functions using this conversion. The get_pytype may be implemented
using the classes and functions
from pytype_function.hpp
NOTE : For backward compatibility this parameter may be passed after
checking if BOOST_PYTHON_SUPPORTS_PY_SIGNATURES is defined (see
here).
|
to_python_converter
synopsisnamespace boost { namespace python { template <class T, class Conversion, bool convertion_has_get_pytype_member=false> struct to_python_converter { to_python_converter(); }; }}
to_python_converter
constructorto_python_converter();
Conversion::convert()
to do its work."noddy.h"
. Because
noddy_NoddyObject
is the ultimate trivial extension type,
the example is a bit contrived: it wraps a function for which all
information is contained in the type of its return value.
#include <boost/python/reference.hpp> #include <boost/python/module.hpp> #include "noddy.h" struct tag {}; tag make_tag() { return tag(); } using namespace boost::python; struct tag_to_noddy { static PyObject* convert(tag const& x) { return PyObject_New(noddy_NoddyObject, &noddy_NoddyType); } static PyTypeObject const* get_pytype() { return &noddy_NoddyType; } }; BOOST_PYTHON_MODULE(to_python_converter) { def("make_tag", make_tag); to_python_converter<tag, tag_to_noddy, true>(); //"true" because tag_to_noddy has member get_pytype }
>>> import to_python_converter >>> def always_none(): ... return None ... >>> def choose_function(x): ... if (x % 2 != 0): ... return to_python_converter.make_tag ... else: ... return always_none ... >>> a = [ choose_function(x) for x in range(5) ] >>> b = [ f() for f in a ] >>> type(b[0]) <type 'NoneType'> >>> type(b[1]) <type 'Noddy'> >>> type(b[2]) <type 'NoneType'> >>> type(b[3]) <type 'Noddy'>
Revised 11 June, 2007
© Copyright Dave Abrahams 2002.