[C++-sig] Beginner - How to extract a Python Class that inherits from C++ Class
Hi,
I was being researching the Boost.Python library, this archive and
stackoverflow but I couldn't find the correct answer.
I tried the following:
-First: I created the C++ Class.
--
user@host ~/ProjectFolder: cat lib/DemiComponent.hpp
#pragma once
#include
namespace DemiWu
{
class Component
{
public:
Component(){};
virtual ~Component(){};
virtual void on_create(){};
};
class ComponentWrap : public Component, public
boost::python::wrapper
{
public:
void empty(){}
virtual void on_create()
{
this->get_override("on_create")();
}
};
void import_component()
{
using namespace DemiWu;
using namespace boost::python;
class_("Component")
.def("on_create", &Component::on_create, &ComponentWrap::empty);
};
};
--
-Second: I exported to Python
--
user@host ~/ProjectFolder: cat lib/DemiWu.hpp
#pragma once
#include
#include
BOOST_PYTHON_MODULE(DemiWu)
{
DemiWu::import_component();
}
--
cat lib/DemiWu.cpp
#include
---
-Third: I used Meson to compile, but I think that is not important. The module
works on python3 interpreter.
--
-Fourth: I wrote a Python Class that inherit form the C++ Class
DemiWu::Component.
--
user@host ~/ProjectFolder: cat build/test.py
import DemiWu
class test(DemiWu.Component):
def __init__(self):
self.x = 10;
self.y = 20;
def on_create(self):
print("(",self.x, ",",self.y,")", sep="")
self.x = self.x + 1
self.y = self.y + 1
--
Fifth: I write a program that extracts the test Python Class.
--
user@host ~/ProjectFolder: cat src/DemiWu.cpp
#include
#include
#include
#include
using namespace boost::python;
using namespace DemiWu;
int main()
{
PyImport_AppendInittab("DemiWu", PyInit_DemiWu);
Py_Initialize();
object main = import("__main__");
object global = main.attr("__dict__");
PySys_SetPath(L".");
global["test"] = import("test");
object obj = eval("test.test()", global);
extract ex(obj);
if(ex.check()){
Component* b=ex();
b->on_create();
std::cout << "SUCCESS\n";
return 0;
} else {
std::cout << "FAIL\n";
return 1;
}
}
--
Sixth: Compile the program successfully.
--
Seventh: Execute and... the output is always "FAIL".
--
How can I fix it? What did I miss?
Thank you for your attention,
Carlos
PS: Sorry for the format of the mail, but I can't express on English well.___
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Re: [C++-sig] Cplusplus-sig Digest, Vol 125, Issue 3
Hello again,
I rewrite part of the code, but I didn't find my error.
My new code is:
cat ../src/DemiWu.cpp
#include
#include
#include
#include
#include
using namespace boost::python;
using namespace DemiWu;
#if PY_MAJOR_VERSION >= 3
# define INIT_MODULE PyInit_DemiWu
extern "C" PyObject* INIT_MODULE();
#else
# define INIT_MODULE initDemiwu
extern "C" void INIT_MODULE();
#endif
int main()
{
PyImport_AppendInittab((char*)"DemiWu", INIT_MODULE);
Py_Initialize();
object main = import("__main__");
object global = main.attr("__dict__");
PySys_SetPath(L".");
global["test"] = import("test"); // How can I check the import?
object funcObj = global["test"].attr("test");
std::cout << std::boolalpha;
std::cout << funcObj.is_none() << "\n"; // funcObj.is_none() == false
object resultObj = funcObj();
std::cout << resultObj.is_none() << "\n"; // resultObj.is_none() == false
// I suppose that in "real" code I need to check every time I use attr
method.
extract exclass(funcObj.attr("__class__").attr("__name__"));
if(exclass.check())
std::cout << "test.test.__class__.__name__: " << exclass() << "\n";
// exclass() == "class"
extract
exclass2(resultObj.attr("__class__").attr("__name__"));
if(exclass2.check())
std::cout << "test.test().__class__.__name__: " << exclass2() <<
"\n"; // exclass2() == "test"
extract exbase(funcObj.attr("__base__").attr("__name__"));
if(exbase.check())
std::cout << "test.test.__base__.__name__: " << exbase() << "\n";
// exbase() == "Component"
// It seems that resultObj is correct, I think that I am using extract<>
function wrong.
extract ex(resultObj);
if(ex.check()){
Component * const b=ex();
b->on_create();
std::cout << "SUCCESS\n";
return 0;
} else {
std::cout << "FAIL\n"; // And again the program jumps here.
return 1;
}
}
And the execution:
./DemiWu
false
false
test.test.__class__.__name__: class
test.test().__class__.__name__: test
test.test.__base__.__name__: Component
FAIL
Thank you for your response
Carlos___
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Re: [C++-sig] Cplusplus-sig Digest, Vol 125, Issue 5
Hi,
I tried that solutions but they didn't work, furthermore, I thought that
polymorphisim only works on pointers. I also tried changing to
reference(Component&) and adding a HeldType in the import module:
class_*/,
boost::noncopyable>("Component", init<>())
but all of this is futile.
Thank you
Carlos___
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Re: [C++-sig] Beginner - How to extract a Python Class that inherits from C++ Class
Hi,
I find the solution, first of all I need to add the initializer on the C++
class import:
class_,
boost::noncopyable>("Component", init<>())
// I additionally added a Holder, but is not necessary.
Then I add the base class initializer on the python class:
class Derived(DemiWu.Component):
def __init__(self):
DemiWu.Component.__init__(self)
I only find a problem, if a python class call the print function it doesn't
work.
Thanks,
Carlos___
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[C++-sig] Beginner How to debug a python class extracted in C++
Hi, I recently started a Boost Python project, https://mail.python.org/pipermail/cplusplus-sig/2020-May/017585.html but I need to debug my python classes extracted in C++ in the main program. The only referece that I find to this topic is in https://www.boost.org/doc/libs/1_73_0/libs/python/doc/html/faq/how_do_i_debug_my_python_extensi.html How can I solve this? I am only using the gdb debugger. Thank you for your attention, Carlos___ Cplusplus-sig mailing list Cplusplus-sig@python.org https://mail.python.org/mailman/listinfo/cplusplus-sig
