Mailman 3 June 2012 - Cplusplus-sig

boost::python embedding error - runtime - Mac OS X - 1.38
by Igor Karpov Oct. 1, 2014

Oct. 1, 2014

Hi, I am trying to run the following program: #include <iostream> #include <Python.h> #include <boost/python.hpp> using namespace boost::python; using namespace std; int main(int argc, char** argv) { { // Using Python/C Py_Initialize(); PyObject* main_module = PyImport_ImportModule("__main__"); PyObject* globals = PyEval_GetGlobals(); PyObject* locals = PyEval_GetLocals(); PyRun_SimpleString("print 'Hello World, from Python/C!'\n"); Py_Finalize(); } { // Using boost::python Py_Initialize(); object main_module = import("__main__"); object main_namespace = main_module.attr("__dict__"); try { object ignored = exec("print 'Hello World, from boost::python!'\n", main_namespace); Py_Finalize(); } catch (error_already_set const& e) { PyErr_Print(); return 1; } } return 0; } on Linux (both x86 and x86_64), with Ubuntu's default version of Boost (1.34.1) installed, I am able to do so as expected: $ ./embed Hello World, from Python/C! Hello World, from boost::python! on Mac OS X, I get a runtime error: $ ./embed Hello World, from Python/C! Bus Error Running with gdb, this is the stack trace: Hello World, from Python/C! Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_PROTECTION_FAILURE at address: 0x00000000 0x00000000 in ?? () (gdb) where #0 0x00000000 in ?? () #1 0x00bb618f in PyEval_GetGlobals () #2 0x00bce0dd in PyImport_Import () #3 0x00bce2b0 in PyImport_ImportModule () #4 0x008127d4 in boost::python::import (name=@0xbffff4a8) at libs/python/src/import.cpp:20 #5 0x00004446 in main (argc=1, argv=0xbffff510) at embed.cc:22 For this Mac, boost version is latest (1.38) and python version is: Python 2.5.4 (r254:67917, Dec 23 2008, 14:57:27) [GCC 4.0.1 (Apple Computer, Inc. build 5363)] on darwin Is this a bug? I attached the source and the cmake file I am using to build, for convenience. Thanks, --Igor.

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sendkeys method
by sam Sept. 30, 2013

Sept. 30, 2013

Hello, Is there away(method) in C/C++ programming that make the software think that someone pressed the OK button, similar to sendkeys in VBS (WshShell.SendKeys ("{Enter}")) Thank you, Sam

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C++ clas with (*args, **kwargs) constructor
by Trigve Siver June 21, 2012

June 21, 2012

Hi, I'm trying to find some solution to my problem but without succes. I need to be able to export C++ class constructor that takes arbitraty arguments (as in python __init__(self, *args, **kwargs). Is it possible to have this kind of constructor? I've tried something like this: BOOST_PYTHON_MODULE(main) { class_<Form, boost::noncopyable, boost::shared_ptr<Form>>("Form") ; } then in main: ... try { object main = import("__main__"); object global(main.attr("__dict__")); boost::python::dict local; exec( "import main\n" "class Form1(main.Form):\n" " def __init__(self, A, *args, **kwargs):\n" " super().__init__(*args, **kwargs)\n\n" , global, local); // Get class object c_form1 = local["Form1"]; // Create instance object form1_instance = object(handle<>(PyObject_CallObject(c_form1.ptr(), make_tuple(1, 2).ptr()))); } catch(error_already_set &) { PyErr_Print(); } But it prints: Traceback (most recent call last): File "<string>", line 4, in __init__ Boost.Python.ArgumentError: Python argument types in Form.__init__(Form1, int) did not match C++ signature: __init__(struct _object *) Which is logical I think because it finds only default constructor. I've tried also raw_constructor from http://wiki.python.org/moin/boost.python/HowTo#A.22Raw.22_constructor but without success. Anyone know if it is somehow possible? Thanks Trigve

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Specified procedure could not be found
by Nagaraju June 21, 2012

June 21, 2012

Hi All, I have written a C++ DLL. That DLL depends on some other libraries. I have kept all those dependent libraries in the release folder. Now in a seperate project in Visual Studio 2008, I used BOOST Python and called a function from one of the classes in C++ DLL. It is compiling fine (compiling it as .pyd), but when I try to import this in python with "import PythonSample", it is throwing following error. Import Error: DLL Load Failed: The specified procedure could not be found. Can you tell me, how to find what went wrong? I tried googling it, but could not find suitable solution. I am using Python 2.7 version. Thanks for your time. Regards, Raju.

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Re: [C++-sig] Cplusplus-sig Digest, Vol 45, Issue 15
by vikas chauhan June 20, 2012

June 20, 2012

On 17 June 2012 15:45, <cplusplus-sig-request(a)python.org> wrote: > Send Cplusplus-sig mailing list submissions to > cplusplus-sig(a)python.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://mail.python.org/mailman/listinfo/cplusplus-sig > or, via email, send a message with subject or body 'help' to > cplusplus-sig-request(a)python.org > > You can reach the person managing the list at > cplusplus-sig-owner(a)python.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Cplusplus-sig digest..." > > > Today's Topics: > > 1. wrapping generic getter/setter functions in boost.python > (vikas chauhan) > 2. Re: wrapping generic getter/setter functions in boost.python > (Jonas Wielicki) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sat, 16 Jun 2012 21:42:56 +0545 > From: vikas chauhan <presentisgood(a)gmail.com> > To: cplusplus-sig(a)python.org > Subject: [C++-sig] wrapping generic getter/setter functions in > boost.python > Message-ID: > <CAG2Q8SbD4CgEH9gx9mNj6XYArEtp5vqL_wUtfo6AiQnZCPR-Eg(a)mail.gmail.com > > > Content-Type: text/plain; charset="iso-8859-1" > > Hi all, > I am pretty new to boost.python and I have been getting some problems > wrapping generic getter/setter functions. > Say for eg. we have class like this. > > class X{ > int a[10]; > public: > int geta(int index) throw(some_exception) { > if(index >= 10 || index <0) > throw some_exception; > return a[index]; > } > void seta(int index, int val) throw(some_exception) { > if(index >= 10 || index < 0) > throw some_exception; > a[index] = value; > } > }; > > I want to add attributes like a0, a1, a2,.. a9 in my python class, wherein > a0 corresponds to a[0] , a1 to a[1] and likewise. > In the boost.python docs ( exposing Class properties ), getter/settter > functions are documented for single value only. > Is it possible to do what I want ( i.e add separate attributes using the > single geta()/seta() functions ) or I need to write some kind of wrapper > functions (each for accessing each a[i]) ? > > i.e, what I want to do is something like this. > > BOOST_PYTHON_MODULE(mymod) > { > using namespace boost::python; > > class_<X>("X") > .add_property("a0", &X::geta, &X::seta) > .add_property("a1", &X::geta, &X::seta) > .. > .. > ; > } > > and passing the arguments to geta ( i.e 0, 1,.. etc ) in someway. > > So, basically what I want is , to avoid unnecessary code bloat. > > regards, > vikas >

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wrapping generic getter/setter functions in boost.python
by vikas chauhan June 16, 2012

June 16, 2012

Hi all, I am pretty new to boost.python and I have been getting some problems wrapping generic getter/setter functions. Say for eg. we have class like this. class X{ int a[10]; public: int geta(int index) throw(some_exception) { if(index >= 10 || index <0) throw some_exception; return a[index]; } void seta(int index, int val) throw(some_exception) { if(index >= 10 || index < 0) throw some_exception; a[index] = value; } }; I want to add attributes like a0, a1, a2,.. a9 in my python class, wherein a0 corresponds to a[0] , a1 to a[1] and likewise. In the boost.python docs ( exposing Class properties ), getter/settter functions are documented for single value only. Is it possible to do what I want ( i.e add separate attributes using the single geta()/seta() functions ) or I need to write some kind of wrapper functions (each for accessing each a[i]) ? i.e, what I want to do is something like this. BOOST_PYTHON_MODULE(mymod) { using namespace boost::python; class_<X>("X") .add_property("a0", &X::geta, &X::seta) .add_property("a1", &X::geta, &X::seta) .. .. ; } and passing the arguments to geta ( i.e 0, 1,.. etc ) in someway. So, basically what I want is , to avoid unnecessary code bloat. regards, vikas

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bad exception conversion
by Wichert Akkerman June 14, 2012

June 14, 2012

I have some glue code that calls a C++ function which can raise an unsuitable_error exception. I have an exception translator which will convert that to a more pythonic version (UnsuitableError), but when I use that I get an "SystemError: 'finally' pops bad exception" error on the python side. As far as I can see my code looks correct, but I suspect I am overlooking something trivial somewhere. using namespace boost::python; class UnsuitableError : public std::exception { public: UnsuitableError() : reasons() { } ~UnsuitableError() throw() {} boost::python::list reasons; }; namespace { PyObject *UnsuitableErrorType = NULL; void translator(const unsuitable_error &e) { std::list<const char*>::const_iterator i; PyObject* unicode; UnsuitableError error=UnsuitableError(); for (i=e.reasons.begin(); i!=e.reasons.end(); i++) { unicode = PyUnicode_FromString(*i); error.reasons.append(boost::python::object(boost::python::handle<>(unicode))); } boost::python::object exc(error); PyErr_SetObject(UnsuitableErrorType, exc.ptr()); } } void export() { object module(handle<>(borrowed(PyImport_AddModule("mypkg.article")))); scope().attr("article")=module; scope module_scope = module; class_<UnsuitableError> UnsuitableErrorClass("UnsuitableError"); UnsuitableErrorClass.def_readonly("reasons", &UnsuitableError::reasons); UnsuitableErrorType=UnsuitableErrorClass.ptr(); register_exception_translator<unsuitable_error>(&translator); }

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Accessing Class Member Function from Python
by Nagaraju June 11, 2012

June 11, 2012

Hi, I have written a sample DLL in C++. It has a class and functions for add, sub, mul and div. I wrote a wrapper class in the same file as BOOST_PYTHON_MODULE(hello). Now when I compiled this DLL, I get Test.DLL. Now from Python, I wrote a script to load this Test.DLL. How can I access add, sub and other functions in my Python script? Request anybody to help me on this. Regards, Raju.

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Boost::Python: overriding and smart pointers
by Sybren A. Stüvel June 11, 2012

June 11, 2012

Dear list, I'm trying to get my head around shared pointers combined with overloaded methods. I want to create instances of my class both in Python and C++, but for some reason I can't get both to work with the same code. I've constructed a minimal example to show you what I'm trying to do. The full C++ code with syntax highlighting can be found at http://pastebin.com/ZqG79QUL Sorry for the long mail, but I saw no other way to show my issues in a clear and unambiguous way. -------------------------------------- class ExampleObject { public: std::string name; ExampleObject(const std::string & name) : name(name) {} virtual ~ExampleObject() {} virtual int some_number() { return 12; } }; typedef boost::shared_ptr<ExampleObject> ExampleObjectPtr; ExampleObjectPtr create_example_object(const std::string & name) { return boost::make_shared<ExampleObject>(name); } void print_name(ExampleObjectPtr object) { std::cout << "Example object named '" << object->name << "', nr = " << object->some_number() << std::endl; } -------------------------------------- These are the class and functions that I want to wrap. The ExampleObject::some_number method should be overridable in Python. To this end, I've created the following wrapper class: -------------------------------------- struct ExampleObject_wrapper : ExampleObject, wrapper<ExampleObject> { ExampleObject_wrapper(const std::string & name) : ExampleObject(name), wrapper<ExampleObject>() {} virtual int some_number(void) override { if( override func_override = this->get_override("some_number")) return func_override(); return default_some_number(); } int default_some_number(void) { return this->ExampleObject::some_number(); } }; typedef boost::shared_ptr<ExampleObject_wrapper> ExampleObject_wrapper_ptr; -------------------------------------- The Python module is declared as follows: -------------------------------------- BOOST_PYTHON_MODULE(wraptest) { def("create_example_object", &create_example_object); def("print_name", &print_name); class_<ExampleObject_wrapper, boost::noncopyable, ExampleObjectPtr> ("ExampleObject", init<const std::string &>()) .def("some_number", &ExampleObject_wrapper::some_number, &ExampleObject_wrapper::default_some_number) ; } -------------------------------------- This is the Python code that I'm testing with: -------------------------------------- from wraptest import * class ExampleSubclass(ExampleObject): def some_number(self): return ExampleObject.some_number(self) * 2 # Test from Python from_py_obj = ExampleSubclass('from python') print_name(from_py_obj) # Test from C++ from_cpp = create_example_object('from C++') print_name(from_cpp) -------------------------------------- When I compile the module (VS2010, Python 3.2.2, Boost 1.48) and run the Python script, I would expect the object created in C++ to show the number 12, and the object created in Python to show the number 24. However, the output is this: Example object named 'from python', nr = 12 Example object named 'from C++', nr = 12 Running a debugger also shows that the ExampleObject_wrapper methods aren't called at all. When I edit the class_<...> line by replacing ExampleObjectPtr with ExampleObject_wrapper_ptr, the from-Python object works just fine, but the from-C++ object gives me an exception: Example object named 'from python', nr = 24 Traceback (most recent call last): File "C:\workspace\rage\scripts\test_wrapping.py", line 13, in <module> from_cpp = create_example_object('from C++') TypeError: No to_python (by-value) converter found for C++ type: class boost::shared_ptr<class ExampleObject> What should I do to be able to instantiate objects in C++ and Python alike? Kind regards, -- Sybren A. Stüvel http://stuvel.eu/

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Re: [C++-sig] Properly copying wrapped classes
by Jay Riley June 9, 2012

June 9, 2012

I replaced my template copy with object bc_copy(object copyable, dict memo){ object copyMod = import("copy"); object deepcopy = copyMod.attr("deepcopy"); BaseClassWrap *newCopyable(new BaseClassWrap(extract<const BaseClassWrap &>(copyable))); BaseClass tmp = boost::python::extract<BaseClass const &>(copyable); object result(tmp); int copyableId = (int)(copyable.ptr()); memo[copyableId] = result; extract<dict>(result.attr("__dict__"))().update( deepcopy(extract<dict>(copyable.attr("__dict__"))(), memo)); return result;} and wrapped class_<BaseClass, boost::shared_ptr<BaseClassWrap> >("BaseClass", init<>()) .def(init<const BaseClass&>()) .def(init<const BaseClassWrap&>()) .def("GetID", &BaseClassWrap::GetIDDefault) .def("Clone", &BaseClassWrap::CloneDefault) .def("Test", &BaseClassWrap::TestDefault) .def("__copy__", &generic__copy__< BaseClass >) .def("__deepcopy__", &bc_copy) ; But I'm still getting the non overriden behaviour. Calling Test on the clone prints out the C++ side code, while the non clone prints out the python side code. > Date: Thu, 7 Jun 2012 17:13:55 -0400 > From: jbosch(a)astro.princeton.edu > To: super24bitsound(a)hotmail.com > Subject: Re: [C++-sig] Properly copying wrapped classes > > On 06/05/2012 12:41 AM, Jay Riley wrote: > > That got rid of the compile time errors. However, On the python side I > > get the following error when I try to clone: > > > > > > File ... line 9 in Clone > > return copy.deepcopy(self) > > File C:\Python27\Lib\copy.py" line 174 in deepcopy > > y = copier(memo) > > TypeError: No to_python (by-value) converter for C++ type: class > > BaseClassWrap > > > > Hmm. I would have expected that to work. As long as BaseClass can be > instantiated itself (i.e. it isn't pure abstract), you could try this in > the copy/deepcopy implementation: > > BaseClass tmp = boost::python::extract<BaseClass const &>(copyable); > object result(tmp); > > (I don't remember which of these types your Copyable template parameter > was, but I'd recommend just trying to write this in a non-template > function until you get it working). > > That will involve one extra copy, but it should invoke the BaseClass > by-value converter instead of the BaseClassWrap by-value converter, and > I *think* that should do the right thing. > > > Jim > > > > > > In the interest of trying it out, I added the BaseClassWrap to the > > python module > > > > class_<BaseClassWrap, bases<BaseClass> >("BaseClassWrap", init<PyObject*>()) > > .def(init<PyObject*, const BaseClass&>()) > > .def(init<PyObject*, const BaseClassWrap&>()) > > .def("__copy__", &generic__copy__< BaseClassWrap >) > > .def("__deepcopy__", &generic__deepcopy__< BaseClassWrap >) > > ; > > > > But this put me back at square one, where self isn't indicative of the > > cloned instance. > > > > Just in the interest of seeing the effect, I changed my python exposing to: > > > > class_<BaseClass, boost::shared_ptr<BaseClassWrap> >("BaseClass", init<>()) > > .def(init<const BaseClass&>()) > > .def(init<const BaseClassWrap&>()) > > .def("GetID", &BaseClassWrap::GetIDDefault) > > .def("Clone", &BaseClassWrap::CloneDefault) > > .def("Test", &BaseClassWrap::TestDefault) > > .def("__copy__", &generic__copy__< BaseClass >) > > .def("__deepcopy__", &generic__deepcopy__< BaseClass >) > > ; > > > > But as expected, the overloading doesn't work on clones made with this > > exposing. Anything else I should try? > > > > Again, thanks for the help so far, appreciate it. > > > > > > > > > > > Date: Mon, 4 Jun 2012 11:52:42 -0400 > > > From: jbosch(a)astro.princeton.edu > > > To: super24bitsound(a)hotmail.com > > > Subject: Re: [C++-sig] Properly copying wrapped classes > > > > > > On 06/04/2012 12:58 AM, Jay Riley wrote: > > > > > > > > Hi Jim, > > > > Thanks for the help so far. From what you said, I should be able to > > change my deepcopy to this correct? > > > > > > > > template<class Copyable> object generic__deepcopy__(object > > copyable, dict memo) { object copyMod = import("copy"); object deepcopy > > = copyMod.attr("deepcopy"); > > > > Copyable *newCopyable(new Copyable(extract<const Copyable > > &>(copyable))); //object > > result(boost::python::detail::new_reference(managingPyObject(newCopyable))); > > > > object result(extract<const Copyable&>(copyable)()); > > > > // HACK: copyableId shall be the same as the result of id(copyable) > > //in Python - // please tell me that there is a better way! (and which > > ;-p) int copyableId = (int)(copyable.ptr()); memo[copyableId] = result; > > > > extract<dict>(result.attr("__dict__"))().update( > > deepcopy(extract<dict>(copyable.attr("__dict__"))(), memo)); > > > > return result; } > > > > When I attempt to compile it gives me the following error: > > > > Error 48 error C2664: 'boost::python::api::object::object(const > > boost::python::api::object&)' : cannot convert parameter 1 from > > 'boost::python::api::object (__cdecl *)(boost::python::extract<T> > > (__cdecl *)(void))' to 'const boost::python::api::object&' > > c:\khmp\src\engine\scripting\python\scripthelpers.h 67 > > > > Did you mean something else? This level of boost python is above my > > head, so I'm a bit lost > > > > > > > > > > It looks like the version I gave you is a bad corner case where the > > > compiler is incapable of parsing a constructor properly when templates > > > and overloaded function-call operators are involved; I always forget > > > exactly when that comes into play (not a compiler bug, just a weird part > > > of the standard, I think). In any case, I think separating it into two > > > lines should fix the problem: > > > > > > const Copyable & tmp = extract<const Copyable &>(copyable); > > > object result(tmp); > > > > > > Let me know if that doesn't work either; at that point I should try to > > > compile it myself and see what's going on. > > > > > > Jim > > > > > > > > > > > > > > > > > > >> Date: Sun, 3 Jun 2012 11:25:38 -0400 > > > >> From: jbosch(a)astro.princeton.edu > > > >> To: cplusplus-sig(a)python.org > > > >> CC: super24bitsound(a)hotmail.com > > > >> Subject: Re: [C++-sig] Properly copying wrapped classes > > > >> > > > >> On 05/31/2012 08:49 PM, Jay Riley wrote: > > > >>> I'm having a problem with some python objects derived in python. > > I have > > > >>> a Clone method that's supposed to make a full copy of these python > > > >>> inherited objects, but it isn't working. The problem is my wrapper > > > >>> class' PyObject* self isn't getting copied, so when I use > > > >>> call_method<>(self, "method name"), self will never point to the > > copied > > > >>> instance. Here's a brief example showing the issue > > > >>> > > > >> > > > >> <snip> > > > >> > > > >>> > > > >>> Sorry about the length, just want to make sure I got everything > > relevant > > > >>> in. When I run this code, it prints: > > > >>> > > > >>> Python Clone > > > >>> Python Side Test. ID: 1 > > > >>> Python Side Test. ID: 1 > > > >>> Original ID 1 > > > >>> Clone ID 1 > > > >>> > > > >>> this is wrong because Clone ID should be 2 (inspecting the object > > > >>> confirms it is 2). Like I said I'm pretty sure the problem is > > that the > > > >>> wrapper class' copy constructor only makes a copy of the > > PyObject* self, > > > >>> not a full copy. This is how every reference doc I saw was doing > > class > > > >>> wrapping, but isn't this wrong? Should we be making a full copy > > of the > > > >>> PyObject*? How would I go about doing that, or otherwise modifying my > > > >>> classes to get the behaviour I expect. > > > >>> > > > >> > > > >> There are a couple of things here that probably need to be addressed: > > > >> > > > >> - Be wary of relying on copy-constructor side effects to demonstrate > > > >> whether something is working; the compiler is allowed to elide copy > > > >> constructors under many conditions, which might result in misleading > > > >> results. That said, I don't think that's what's causing your problem > > > >> here (or at least not all of it). > > > >> > > > >> - Your implementations of __copy__ and __deepcopy__ won't work with > > > >> polymorphic wrapper classes, because they construct a BaseClass > > instance > > > >> and tell Boost.Python to wrap it by managing the new reference. That > > > >> necessarily makes a Python object that holds a BaseClass object, > > not one > > > >> that holds a BaseClassWrap object. If you want to get a BaseClassWrap > > > >> Python object, you want to pass it by value to Boost.Python; that > > should > > > >> invoke the BaseClassWrap copy constructor and pass it a new > > PyObject* to > > > >> manage (so it doesn't have to copy the PyObject* itself). > > > >> > > > >> I think that just means you can remove the "managingPyObject" > > function, > > > >> and instead use: > > > >> > > > >> object result(extract<const Copyable&>(copyable)()); > > > >> > > > >> > > > >> HTH > > > >> > > > >> Jim > > > > > > > >

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