Mailman 3 October 2002 - Cplusplus-sig

Python + Boost Python V2 + downcasting
by Nicolas Lelong Nov. 7, 2002

Nov. 7, 2002

Hello, I'm experiencing some embedding+extending with BPLv2 - and I could not find any answer to this simple question : I have, say, a c++ class 'Base' and a c++ class 'Derived': class Base { public: virtual int do_stuff() { return 0; } }; class Derived { public: virtual int do_more() { return 100; } }; class ObjectServer { public: Base* getObject(unsigned id) { return m_objects[id]; } Base* m_objects[12]; } declared in my module like this: class_<Base>("Base") .def("do_stuff", &Base::do_stuff); class_<Derived, bases<Base> >("Derived") .def("do_more", &Derived::do_more); class_<ObjectServer>("ObjectServer") .def("getObject", &ObjectServer::getObject, return_internal_reference<>()); everything works fine - except that I can't get python to see the _real_ class of the objects returned by getObject. I tried the following: ... obj = objectServer.getObject(0) print isinstance(obj, Base) print isinstance(obj, Derived) print issubclass(Derived, Base) print obj.__class__ and I get, when 'obj' is really a 'Derived*' ... 1 0 1 module.Base how can I get to know that an object is an instance of Derived ?! is there a builtin way in Python ? a BPL v2 way ? I even thought about implementing my own 'isinstance' function but I'm not familiar enough with boost python & python !!... Any help or advice will be _greatly_ appreciated :) Thanks in advance, Nicolas. PS. Please CC your response to n_lelong(a)hotmail.com as I'm not a regular contributor to this list!

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Boost V1 build on Solaris
by Paul F. Kunz Nov. 6, 2002

Nov. 6, 2002

I'm trying to build V1 boost::python on Solaris from boost_1_28. tersk06> $GCC_ROOT_DIRECTORY/bin/gcc -v Reading specs from /afs/slac/package/gcc/gcc-3/3.1.1/sun4x_58/bin/../lib/gcc-lib/sparc-sun-solaris2.8/3.1.1/specs Configured with: ../../src/gcc-3.1.1/configure --disable-libffi --without-libffi --prefix=/afs/slac.stanford.edu/package/gcc/gcc-3/3.1.1/sun4x_58 --srcdir=../../src/gcc-3.1.1 --enable-shared --enable-version-specific-runtime-libs Thread model: posix gcc version 3.1.1 tersk06> pwd /a/surrey07/g.ek.novadata/data/pfkeb/boost_1_28_0 tersk06> bjam "-sTOOLS=gcc" --------------------------------------------------------------------- skipping Boost.Python library build You can configure the location of your python installation, by setting: PYTHON_ROOT - currently "/afs/slac/package/python/sun4x_59/2.0" PYTHON_VERSION - The 2-part python Major.Minor version number (e.g. "2.2", NOT "2.2.1") - currently "2.0" The following are automatically configured from PYTHON_ROOT if not otherwise set: PYTHON_INCLUDES - path to Python #include directories; currently "/afs/slac/package/python/sun4x_59/2.0/include/python2.0" PYTHON_LIB_PATH - path to Python library; currently "/afs/slac/package/python/sun4x_59/2.0/lib/python2.0/config" PYTHON_STDLIB_PATH - path to Python standard library modules; currently "/afs/slac/package/python/sun4x_59/2.0/lib/python2.0" --------------------------------------------------------------------- ...found 414 targets... So the rest of boost built but not python. I've not had problems under Linux. Any hints?

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RE: [C++-sig] boost.python coredump in debug mode..?
by Bjorn Pettersen Nov. 2, 2002

Nov. 2, 2002

> From: David Abrahams [mailto:dave@boost-consulting.com] > > "Bjorn Pettersen" <BPettersen(a)NAREX.com> writes: > > > > From: David Abrahams [mailto:dave@boost-consulting.com] > > > > > > "Bjorn Pettersen" <BPettersen(a)NAREX.com> writes: > > > > > > > I'm working through the tutorial introduction, and I'm getting a > > > > strange coredump in a debug build. I'm at the struct > World example > > > > with a constructor: > > [snip] > > > > > > Perhaps you didn't carefully read the section on build > > > variants at http://www.boost.org/libs/python/building.html? > > > > I got a 404 with that link, but I did read the Build > Variants section > > at http://www.boost.org/libs/python/doc/building.html and I must be > > dense because I still can't get it to work. I included > > <boost/python/detail/wrap_python.hpp> at the top of my > file, defined > > _DEBUG, and linked with either boost_python.lib or > > boost_python_debug.lib and I'm always getting the coredump. > I'm sure > > I'm missing something obvious.... > > What was the test case again? >>> import hello >>> x = hello.World('hi') >>> hello.World('hi') # this call... <hello.World object at 0x0089E748> >>> x.greet() # ... causes this to coredump with the code at http://www.boost.org/libs/python/doc/tutorial/doc/constructors.html -- bjorn

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Re: modules and separate compilation
by Ralf W. Grosse-Kunstleve Oct. 31, 2002

Oct. 31, 2002

--- Francois Ostiguy <ostiguy(a)fnal.gov> wrote: > I have a very large collection of classes which should all be part of the > same module. Is there any way of separately compiling the module interface > code (i.e boost.python code) for different groups of classes belonging to > the *same* module ... or do I absolutely need to use a single file with > all the class interface declations within the scope of a single instance > of I believe your question is answered in this message: http://mail.python.org/pipermail/c++-sig/2002-October/002345.html Ralf P.S.: Please post to c++-sig(a)python.org, not to c++-sig-owner. __________________________________________________ Do you Yahoo!? HotJobs - Search new jobs daily now http://hotjobs.yahoo.com/

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More MacOSX & Python - 2.3
by Rene Rivera Oct. 31, 2002

Oct. 31, 2002

Well thanks again to Ralf for doing some of the MacOSX work... and figuring out how to install the latest Python as a framework. Good news is... * Extensions and libboost_python build and link. That is the ones that compile. * Of the ones that produce an extension they are loaded by the Python interpreter. * Of the ones that load, some of them seem to run to completion, and what looks like without errors. Bad news... * Only a small number of them compile. The single compile problem is this error: In file included from /net/taipan/scratch1/grafik/boost/boost/python/class.hpp:11, from args.cpp:10: /net/taipan/scratch1/grafik/boost/boost/python/bases.hpp:19: parse error before numeric constant /net/taipan/scratch1/grafik/boost/boost/python/bases.hpp:24: confused by earlier errors, bailing out * Of the ones that compile and load, the majority seem to just hang there doing nothing for some time. After some short period of time (~1 minute) I killed the Python interpreter. Don't know why this is, but it could be something as silly as it deciding to open a dialog box I can't see and is waiting for never to arrive feedback. There is one change I had to make to Boost.Python code to even get this far: Index: rvalue_from_python_data.hpp =================================================================== RCS file: /cvsroot/boost/boost/boost/python/converter/rvalue_from_python_data.hpp,v retrieving revision 1.10 diff -b -u -2 -r1.10 rvalue_from_python_data.hpp --- rvalue_from_python_data.hpp 12 Oct 2002 15:37:33 -0000 1.10 +++ rvalue_from_python_data.hpp 31 Oct 2002 04:57:49 -0000 @@ -98,5 +98,5 @@ && !defined(BOOST_PYTHON_SYNOPSIS) /* Synopsis' OpenCXX has trouble parsing this */ // This must always be a POD struct with m_data its first member. - BOOST_STATIC_ASSERT(BOOST_PYTHON_OFFSETOF(rvalue_from_python_storage<T>,stage1) == 0); + //BOOST_STATIC_ASSERT(BOOST_PYTHON_OFFSETOF(rvalue_from_python_storage<T>,stage1) == 0); # endif If that BOOST_STATIC_ASSERT is not commented out the compiler chokes with an can't-do-that/unimplemented error. I'm attachinng the test output just in case it usefull in some form. The setup for compilation is like so: PYTHON_ROOT=/Library/Frameworks/Python.framework/Versions/2.3 PYTHON_VERSION=2.3 -- grafik - Don't Assume Anything -- rrivera(a)acm.org - grafik(a)redshift-software.com -- 102708583@icq - Grafik666@AIM - Grafik(a)jabber.org

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RE: [C++-sig] How do I wrap a C++ object to a PyObject*
by Bjorn Pettersen Oct. 31, 2002

Oct. 31, 2002

> From: Ralf W. Grosse-Kunstleve [mailto:rwgk@yahoo.com] > > --- David Abrahams <dave(a)boost-consulting.com> wrote: > > "Bjorn Pettersen" <BPettersen(a)NAREX.com> writes: > > > I've looked through the documentation but haven't found anything > > > obvious... > > > > Let's see. You have a wrapped C++ class somewhere? > > If so, you can write in __main__: > > > > import some_boost_python_module > > x = some_boost_python_module.some_class(some_arg) > > > > But this is trivially explained in the docs, so you must mean > > something else... > > I believe he wants to do this from C++. I don't know what > __main__ is, but I am guessing that his problem is solved by > using a construct like this: > > scope().attr("key") = value; > > which I believe is just a shorthand for > > scope().attr("key") = object(value); > > This sets an attribute in the importing module. > value can be any object that is convertible from C++ to > Python, including but not limited to instances of a > user-defined classes X with a corresponding class_<X> statement. Cool. Thanks! -- bjorn

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How do I wrap a C++ object to a PyObject*
by Bjorn Pettersen Oct. 31, 2002

Oct. 31, 2002

I'm trying to embed Python in my C++ application, and it looks pretty easy to convert a PyObject* returned from PyRun_String using the 'extract' functionality. How do I go the other way? I.e. I want to set a variable in __main__ to an instance of my C++ class (or pass them as arguments to PyObject_CallFunctionObjArgs). With SIP there was a function called sipMapCppToSelf used like this: void set(const std::string& name, const LegalStatusCode& value) { PyObject* key = PyString_FromString(name.c_str()); PyObject* val = sipMapCppToSelf(&value, sipClass_LegalStatusCode); PyDict_SetItem(mainmodule, key, val); Py_DECREF(key); Py_DECREF(val); } I've looked through the documentation but haven't found anything obvious... -- bjorn

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RE: [C++-sig] boost.python coredump in debug mode..?
by Bjorn Pettersen Oct. 30, 2002

Oct. 30, 2002

> From: David Abrahams [mailto:dave@boost-consulting.com] > > "Bjorn Pettersen" <BPettersen(a)NAREX.com> writes: > > > I'm working through the tutorial introduction, and I'm getting a > > strange coredump in a debug build. I'm at the struct World example > > with a constructor: [snip] > > Perhaps you didn't carefully read the section on build > variants at http://www.boost.org/libs/python/building.html? I got a 404 with that link, but I did read the Build Variants section at http://www.boost.org/libs/python/doc/building.html and I must be dense because I still can't get it to work. I included <boost/python/detail/wrap_python.hpp> at the top of my file, defined _DEBUG, and linked with either boost_python.lib or boost_python_debug.lib and I'm always getting the coredump. I'm sure I'm missing something obvious.... -- bjorn

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Creating python objects from C++
by tom Oct. 30, 2002

Oct. 30, 2002

Hi I'm embedding a Python interpreter in a C++ application and am trying to use Boost.Python to connect the two. I've got it hooked up and can access my application from Python, and subclass C++ objects inside the interpreter and it works perfectly! The tricky part is that I need to drive this process from the C++ side, instead of the Python side. I need the ability to extend C++ objects with Python methods, but to create and maintain those objects from C++. I haven't seen anything in the mailing list or the docs about how to do this. I've been trying to pass back the PyTypeObject* for a given class back to C++ and create the objects using the _PyObject_New function described in the Python documentation, but I haven't been able to pass it back to C++. I get "TypeError: No registered converter was able to extract a C++ reference to type struct _typeobject from this Python object of type Boost.Python.class." Is there a better way to do this? Or if not, what's the best way to write a converter to pull out the PyTypeObject information? Thanks Tom McCormack

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boost.python coredump in debug mode..?
by Bjorn Pettersen Oct. 30, 2002

Oct. 30, 2002

I'm working through the tutorial introduction, and I'm getting a strange coredump in a debug build. I'm at the struct World example with a constructor: >>> import hello >>> x = hello.World('hi') >>> x.greet() 'hi' >>> hello.World('hi') # if I remove this I don't get a coredump <hello.World object at 0x0089E748> >>> x.greet() [coredump] The exact message is "Debug Assertion Failed! File: dbgheap.c Line 1044 Expression _CrtIsValidHeapPointer(pUserData)". I'm using msvc6 on winxp and the release version works fine. Am I doing something wrong? -- bjorn Bjorn Pettersen NAREX Inc. 303.526.4000 ext. 312 303.526.5130 fax www.narex.com

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