Mailman 3 April 2009 - 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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CMake and getting starting with boost.python
by Braddock Gaskill Aug. 5, 2011

Aug. 5, 2011

Yesterday I became a boost.python user, after years of heavy SWIG usage. I would have started using boost.python years ago except for the bjam learning curve. I spent hours TRYING on multiple occasions, but got lost every time trying to get the page one example to build with bjam. Here is how to build the "greet" example with a four line CMake file: cat >>CMakeLists.txt <<EOF LINK_LIBRARIES(boost_python) INCLUDE_DIRECTORIES("/usr/include/python2.5") LINK_DIRECTORIES("/usr/lib/python2.5") # Not needed? ADD_LIBRARY(hello SHARED hello.cpp) EOF You WILL have to `mv libhello.so hello.so` after building. Works for me under Ubuntu Linux 6.10 after apt-get install cmake python2.5-dev boost-python-dev cmake make mv libhello.so hello.so ipython In [1]: import hello In [2]: hello.greet() Out[2]: 'hello, world' Boost.Python has been a joy to learn and use since I got past bjam. I had a moderately large API wrapped in just my first couple hours of learning (less time than I spent messing with bjam). Any additional advice for using CMake to build boost.python? Braddock Gaskill

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How to import a boost::python dll in windows?
by ichijoji Aug. 5, 2011

Aug. 5, 2011

I'm trying to port some research code that uses boost::python to expose a library to python to windows, but I'm having trouble importing the dll into python. I'm compiling using msvc 2005 and using python 2.5, but when I try to import the module I get this: Traceback (most recent call last): File "main.py", line 1, in <module> import object File "c:\code\sge\code\scripts\object.py", line 1, in <module> import sge ImportError: No module named sge My module is named sge and I'm compiling to sge.dll. Is there some obvious reason why python wouldn't be able to find my dll? When I compile on linux into an so this code works fine. -- View this message in context: http://www.nabble.com/How-to-import-a-boost%3A%3Apython-dll-in-windows--tf3… Sent from the Python - c++-sig mailing list archive at Nabble.com.

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Getting object for PyObject (reference counting)
by Murray Cumming Feb. 11, 2010

Feb. 11, 2010

I can't find any definitive documentation that tells me how I should get a boost::python::object to wrap an existing PyObject*. I guess that there's a way to do it that uses an existing reference, and a way that takes an extra reference. -- murrayc(a)murrayc.com www.murrayc.com www.openismus.com

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pygccxml and multidimensional arrays
by Davidson, Josh June 19, 2009

June 19, 2009

Machine: x86_64 running RH EL 5.0 Pygccxml version 1.0.0 Gcc-xml version 0.9.0 If I create a struct similar to: typedef struct { uint16_t a[4][2][3]; } blah; And use pygccxml to parse it, the type attribute for the field "a" is set to: uint16_t[3][2][4]. Does anyone know why the dimensions are reversed?

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numpy.int32 -> double?
by Bruce Sherwood April 28, 2009

April 28, 2009

I'm not sure this is the right forum for my question; it's quite possible that this is a numpy question. VPython (vpython.org) is the name of Python plus the 3D Visual module, which is mostly written in C++ and connected to Python using the Boost libraries. Visual imports numpy. When I build Visual for Python 2.6 and numpy 1.3.0, I get a failure on something that works on Python 2.5 with numpy 1.2.1. There is a vector(double,double,double) class in Visual which now fails if handed numpy.int32 arguments (works fine with numpy.float64 arguments). I was using Boost 1.35 with Python 2.5 and am using Boost 1.38 with Python 2.6. Any ideas or suggestions? Thanks. Bruce Sherwood

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pybindgen add_function_as_constructor
by Robin Gilks April 28, 2009

April 28, 2009

Following on from my expanding embedded code thread, I'm making progress in that if I hack the class instantiation in the wrapper that pybindgen produces I can get it all to work. With that in mind, I'm trying to use add_function_as_constructor but it won't let me use a 'void *' or 'PyObject *' pointer as a parameter. I have to use 'uint32_t *' and then edit the code!! My generator code looks like this... testclass = mod.add_class('testclass') testclass.add_function_as_constructor('PyCObject_AsVoidPtr', None, [Parameter.new(''PyObject *', 'instance', transfer_ownership = False)]) which results in the traceback of... Traceback (most recent call last): File "testclassgen.py", line 31, in <module> my_module_gen(sys.stdout) File "testclassgen.py", line 28, in my_module_gen mod.generate(FileCodeSink(out_file) ) File "/usr/local/lib/python2.5/site-packages/pybindgen/module.py", line 839, in generate self.do_generate(sink_manager, module_file_base_name) File "/usr/local/lib/python2.5/site-packages/pybindgen/module.py", line 721, in do_generate class_.generate(sink, self) File "/usr/local/lib/python2.5/site-packages/pybindgen/cppclass.py", line 1481, in generate have_constructor = self._generate_constructor(code_sink) File "/usr/local/lib/python2.5/site-packages/pybindgen/cppclass.py", line 1620, in _generate_constructor overload.generate(code_sink) File "/usr/local/lib/python2.5/site-packages/pybindgen/overloading.py", line 183, in generate (code_sink,), {}, self.all_wrappers[0]) File "/usr/local/lib/python2.5/site-packages/pybindgen/utils.py", line 124, in call_with_error_handling return callback(*args, **kwargs) File "/usr/local/lib/python2.5/site-packages/pybindgen/cppmethod.py", line 520, in generate % self._class.name) AssertionError: something went wrong with the type handlers; constructors need parameter names, yet no names were given for the class testclass constructor If I change the 'PyObject *' to a 'void *' I get...Traceback (most recent call last): File "testclassgen.py", line 31, in <module> my_module_gen(sys.stdout) File "testclassgen.py", line 16, in my_module_gen testclass.add_function_as_constructor('PyCObject_AsVoidPtr', None, [Parameter.new('void *', 'instance', transfer_ownership = False)]) File "/usr/local/lib/python2.5/site-packages/pybindgen/typehandlers/base.py", line 1221, in new param_type_matcher.lookup(ctype) File "/usr/local/lib/python2.5/site-packages/pybindgen/typehandlers/base.py", line 1350, in lookup raise TypeLookupError(tried_names) pybindgen.typehandlers.base.TypeLookupError: ['void *'] but looking at pybindgen-0.10.0/pybindgen/typehandlers/base.py it looks like at least void * should be OK!! I either still missing something (very likely) or there is a problem here! -- Robin ======================================================================= This email, including any attachments, is only for the intended addressee. It is subject to copyright, is confidential and may be the subject of legal or other privilege, none of which is waived or lost by reason of this transmission. If the receiver is not the intended addressee, please accept our apologies, notify us by return, delete all copies and perform no other act on the email. Unfortunately, we cannot warrant that the email has not been altered or corrupted during transmission. =======================================================================

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Expanding embedded code
by Robin Gilks April 24, 2009

April 24, 2009

A difficult question to put a title to so I'll paint a brief scenario... The application is written in c++ It receives a data message and instantiates a message decoder class. Based on the contends that are extracted into the class variables, a response is built by instantiating an encoder class and setting its class variables with setter methods. At this point I want to pass control over to a Python script so that it can modify the encoder class variables (via the accessors) if required before the response is actually sent. These accessors would form an extension to the interpreter. Note that doing more work in the Python script is not an option - too much data in too short a time!! I've got as far as embedding the interpreter and calling the correct method in a script but I've hit a problem in extending the interpreter to access the decoder and encoder classes in my main app. Note that I want to access the specific instances of the classes to manipulate the class variables that were set before entering the Python domain. Now the questions... * My understanding is that extending Python *always* uses a dynamically loaded library (i.e. a run time linkage) as part of the import mechanism - is there something in the C/API that will override this? If I load an extra library, even one built from the same source as my classes in the main app, I won't be accessing the same instance of them. * Since the class has already be instantiated in the main app, how do I pass the instance pointer to Python so that it can pass it back when it makes the extension call to my class methods (assuming I can get past the previous point!!). I would assume that it involves a PyCObject but none of the code examples I have found give much clue as to how the extension is invoked from the Python side with the instance pointer apart from when using a new_class constructor call. I'm sure I'm close, I just can't get past the two points above... Cheers -- Robin ======================================================================= This email, including any attachments, is only for the intended addressee. It is subject to copyright, is confidential and may be the subject of legal or other privilege, none of which is waived or lost by reason of this transmission. If the receiver is not the intended addressee, please accept our apologies, notify us by return, delete all copies and perform no other act on the email. Unfortunately, we cannot warrant that the email has not been altered or corrupted during transmission. =======================================================================

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python objects not is the same in separated modules
by Renato Araujo April 22, 2009

April 22, 2009

Hi guys, I found a problems with my binds when I work with separated modules. In my function where return a c++ pointer to a object, this not return the same python object used in setter function. The main point here is because this works fine when all classes are exported in the same module but when I split the module this stop work. Module pybase ========================= class Base { private: Base *_child; public: void setChild(Base *parent); Base* child(); virtual ~Base(); }; class BaseWrapper : public Base, public wrapper<Base> { public: typedef class_<BaseWrapper, noncopyable> class_type; }; BOOST_PYTHON_MODULE(pybase) { BaseWrapper::class_type foo("Base"); foo.def("setChild", &Base::setChild); foo.def("child", &Base::child, return_internal_reference<>()); } Module pyother =================================== class Other : public Base { public: virtual ~Other(); }; class OtherWrapper : public Other, public wrapper<Other> { public: typedef class_<OtherWrapper, bases<Base>, noncopyable > class_type; }; BOOST_PYTHON_MODULE(pyother) { OtherWrapper::class_type other("Other"); } Python test ========================================== #create a class exported in module pyother t = Other() #create a class exported in module pybase o = Base() #set base child o.setChild(t) #get object used in previous function c = o.child() #compare both object this need be true print t print c print t == c this happen when I use "Other" object in "setChild" and "child" function. when I use "Base" object works fine. I put a small example annexed in this e-mail. -- BR Renato Araujo Oliveira Filho

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Extending python and using debug interpreter on Linux
by Brian O'Kennedy April 22, 2009

April 22, 2009

Hi, I've built a local copy of Python with PY_DEBUG enabled and tried import a simple module which only defs a single c++ function returning a std::string. My test involves importing the module, and then quitting the interpreter; I'm not trying to call anything in the module. This works as expected in Release mode on linux (as well as working correctly on Windows for Release and Debug(with PY_DEBUG). However, on Linux using the debug interpreter I get a "Fatal Python error: UNREF invalid object" with the callstack as follows: #0 0xb7f3e430 in __kernel_vsyscall () #1 0xb7bf48a0 in raise () from /lib/tls/i686/cmov/libc.so.6 #2 0xb7bf6268 in abort () from /lib/tls/i686/cmov/libc.so.6 #3 0xb7ea2837 in Py_FatalError (msg=0xb7ed7ed4 "UNREF invalid object") at Python/pythonrun.c:1561 #4 0xb7dfe3d2 in _Py_ForgetReference (op=0xb7b87754) at Objects/object.c:1918 #5 0xb7dfe431 in _Py_Dealloc (op=0xb7b87754) at Objects/object.c:1937 #6 0xb7df2b12 in insertdict (mp=0xb7b89714, key=0xb7b7a208, hash=1901421549, value=0xb7efa8a8) at Objects/dictobject.c:420 #7 0xb7df33e0 in PyDict_SetItem (op=0xb7b89714, key=0xb7b7a208, value=0xb7efa8a8) at Objects/dictobject.c:645 #8 0xb7e8f4b7 in PyImport_Cleanup () at Python/import.c:475 #9 0xb7e9f44c in Py_Finalize () at Python/pythonrun.c:399 #10 0xb7ea2a1e in Py_Exit (sts=0) at Python/pythonrun.c:1618 #11 0xb7ea0e0a in handle_system_exit () at Python/pythonrun.c:1054 #12 0xb7ea0e3b in PyErr_PrintEx (set_sys_last_vars=1) at Python/pythonrun.c:1064 #13 0xb7ea0af1 in PyErr_Print () at Python/pythonrun.c:978 #14 0xb7ea00ca in PyRun_InteractiveOneFlags (fp=0xb7d23420, filename=0xb7eeaf07 "<stdin>", flags=0xbf83f4ac) at Python/pythonrun.c:795 #15 0xb7e9fcda in PyRun_InteractiveLoopFlags (fp=0xb7d23420, filename=0xb7eeaf07 "<stdin>", flags=0xbf83f4ac) at Python/pythonrun.c:723 #16 0xb7e9fb06 in PyRun_AnyFileExFlags (fp=0xb7d23420, filename=0xb7eeaf07 "<stdin>", closeit=0, flags=0xbf83f4ac) at Python/pythonrun.c:692 #17 0xb7eb0ade in Py_Main (argc=1, argv=0xbf83f5b4) at Modules/main.c:532 #18 0x080485e2 in main (argc=Cannot access memory at address 0x3392 Anyone have any ideas what is going wrong? I'm aware that there are issues with Boost Python and Py_Finalize, but is that what is causing this problem? Using Boost 1.38.0 and Python 2.5.4, both built from source on both Linux Ubuntu gcc42 and Windows Vista using VS2005. Thanks, Brian ________________________________________________________________________ This e-mail, and any attachment, is confidential. If you have received it in error, do not use or disclose the information in any way, notify me immediately, and please delete it from your system. ________________________________________________________________________

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