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Boost.Python supports docstrings with automatic appending of Pythonic
and C++ signatures. This feature is implemented by class function_doc_signature_generator. The
class uses all of the overloads, supplied arg names and default values,
as well as the user-defined docstrings, to generate documentation for
a given function.
The class has only one public function which returns a list of strings documenting the overloads of a function.
namespace boost { namespace python { namespace objects { class function_doc_signature_generator { public: static list function_doc_signatures(function const *f); }; }}}
#include <boost/python/module.hpp> #include <boost/python/def.hpp> #include <boost/python/args.hpp> #include <boost/python/tuple.hpp> #include <boost/python/class.hpp> #include <boost/python/overloads.hpp> #include <boost/python/raw_function.hpp> using namespace boost::python; tuple f(int x = 1, double y = 4.25, char const* z = "wow") { return make_tuple(x, y, z); } BOOST_PYTHON_FUNCTION_OVERLOADS(f_overloads, f, 0, 3) struct X { tuple f(int x = 1, double y = 4.25, char const* z = "wow") { return make_tuple(x, y, z); } }; BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS(X_f_overloads, X::f, 0, 3) tuple raw_func(tuple args, dict kw) { return make_tuple(args, kw); } BOOST_PYTHON_MODULE(args_ext) { def("f", f, (arg("x")=1, arg("y")=4.25, arg("z")="wow") , "This is f's docstring" ); def("raw", raw_function(raw_func)); def("f1", f, f_overloads("f1's docstring", args("x", "y", "z"))); class_<X>("X", "This is X's docstring", init<>(args("self"))) .def("f", &X::f , "This is X.f's docstring" , args("self","x", "y", "z")) ; }
Python code:
>>> import args_ext >>> help(args_ext) Help on module args_ext: NAME args_ext FILE args_ext.pyd CLASSES Boost.Python.instance(__builtin__.object) X class X(Boost.Python.instance) | This is X's docstring | | Method resolution order: | X | Boost.Python.instance | __builtin__.object | | Methods defined here: | | __init__(...) | __init__( (object)self) -> None : | C++ signature: | void __init__(struct _object *) | | f(...) | f( (X)self, (int)x, (float)y, (str)z) -> tuple : This is X.f's docstring | C++ signature: | class boost::python::tuple f(struct X {lvalue},int,double,char const *) | | ................. | FUNCTIONS f(...) f([ (int)x=1 [, (float)y=4.25 [, (str)z='wow']]]) -> tuple : This is f's docstring C++ signature: class boost::python::tuple f([ int=1 [,double=4.25 [,char const *='wow']]]) f1(...) f1([ (int)x [, (float)y [, (str)z]]]) -> tuple : f1's docstring C++ signature: class boost::python::tuple f1([ int [,double [,char const *]]]) raw(...) object raw(tuple args, dict kwds) : C++ signature: object raw(tuple args, dict kwds)
To support Pythonic signatures the converters should supply a get_pytype function returning a pointer
to the associated PyTypeObject.
See for example ResultConverter or to_python_converter. The classes
in this header file are meant to be used when implmenting get_pytype. There are also _direct versions of the templates of
class T
which should be used with undecorated type parameter, expected to be
in the conversion registry when the module loads.
This template generates a static get_pytype
member returning the template parameter.
namespace boost { namespace python { namespace converter{ template < PyTypeObject const *pytype > class wrap_pytype { public: static PyTypeObject const *get_pytype(){return pytype; } }; }}}
This template should be used with template parameters which are (possibly
decorated) types exported to python using class_. The generated a static
get_pytype member returns
the corresponding python type.
namespace boost { namespace python { namespace converter{ template < class T > class registered_pytype { public: static PyTypeObject const *get_pytype(); }; }}}
This template generates a static get_pytype
member which inspects the registered from_python
converters for the type T
and returns a matching python type.
namespace boost { namespace python { namespace converter{ template < class T > class expected_from_python_type { public: static PyTypeObject const *get_pytype(); }; }}}
This template generates a static get_pytype
member returning the python type to which T
can be converted.
namespace boost { namespace python { namespace converter{ template < class T > class to_python_target_type { public: static PyTypeObject const *get_pytype(); }; }}}
This example presumes that someone has implemented the standard noddy
example module from the Python documentation, and placed the corresponding
declarations in "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.
C++ module definition:
#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 #if defined BOOST_PYTHON_SUPPORTS_PY_SIGNATURES //unnecessary overhead if py signatures are not supported : wrap_pytype<&noddy_NoddyType> //inherits get_pytype from wrap_pytype #endif { static PyObject* convert(tag const& x) { return PyObject_New(noddy_NoddyObject, &noddy_NoddyType); } }; BOOST_PYTHON_MODULE(to_python_converter) { def("make_tag", make_tag); to_python_converter<tag, tag_to_noddy #if defined BOOST_PYTHON_SUPPORTS_PY_SIGNATURES //invalid if py signatures are not supported , true #endif >(); //"true" because tag_to_noddy has member get_pytype }
The following example registers to and from python converters using the templates expected_from_python_type and to_pyhton_target_type.
#include <boost/python/module.hpp> #include <boost/python/def.hpp> #include <boost/python/extract.hpp> #include <boost/python/to_python_converter.hpp> #include <boost/python/class.hpp> using namespace boost::python; struct A { }; struct B { A a; B(const A& a_):a(a_){} }; // Converter from A to python int struct BToPython #if defined BOOST_PYTHON_SUPPORTS_PY_SIGNATURES //unnecessary overhead if py signatures are not supported : converter::to_python_target_type<A> //inherits get_pytype #endif { static PyObject* convert(const B& b) { return incref(object(b.a).ptr()); } }; // Conversion from python int to A struct BFromPython { BFromPython() { boost::python::converter::registry::push_back ( &convertible , &construct , type_id< B >() #if defined BOOST_PYTHON_SUPPORTS_PY_SIGNATURES //invalid if py signatures are not supported , &converter::expected_from_python_type<A>::get_pytype//convertible to A can be converted to B #endif ); } static void* convertible(PyObject* obj_ptr) { extract<const A&> ex(obj_ptr); if (!ex.check()) return 0; return obj_ptr; } static void construct( PyObject* obj_ptr, converter::rvalue_from_python_stage1_data* data) { void* storage = ( (converter::rvalue_from_python_storage< B >*)data)-> storage.bytes; extract<const A&> ex(obj_ptr); new (storage) B(ex()); data->convertible = storage; } }; B func(const B& b) { return b ; } BOOST_PYTHON_MODULE(pytype_function_ext) { to_python_converter< B , BToPython #if defined BOOST_PYTHON_SUPPORTS_PY_SIGNATURES //invalid if py signatures are not supported ,true #endif >(); //has get_pytype BFromPython(); class_<A>("A") ; def("func", &func); } >>> from pytype_function_ext import * >>> print func.__doc__ func( (A)arg1) -> A : C++ signature: struct B func(struct B)