Mailman 3 July 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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Fw: g++ compiler limitations other than -ftemplate-depth-n and -DBOOST_PYTHON_MAX_ARITY ?
by Christopher A Mejia Sept. 20, 2009

Sept. 20, 2009

Stefan / cplusplus-sig, Based on Stefan's encouragement, I developed a minimal complete test case exhibiting this problem, contained in the attached files. The compilation command I used was: g++ -DBOOST_PYTHON_MAX_ARITY=40 -I/data/cmejia/install/boost_1_39_0 -I/data/include/python2.6 -c -o foo.o foo.cpp As I explained earlier in the first message of this thread, this fails to compile, but if I remove one double argument towards the end (i.e. edit out one line of foo.hpp and two lines of foo.cpp) it does compile successfully. I would appreciate any further insight into this problem, and hopefully we can use this test case to make Boost.Python an even better tool. Thanks in advance, --Chris P.S. Unfortunately, I was unable to include preprocessed source from "g++ ... -E foo.cpp" because the result was too large for the mailing list system. Christopher A Mejia wrote: > Stefan, > > Thanks for your response. The API that I am trying to wrap is the > Data Client Server portion of the U.S. Naval Research Labs' SIMDIS > Analysis & Display Tool (simdis.nrl.navy.mil). This is free software, > but does require registration and there is a human in the loop of the > approval process. Anyway, I don't feel comfortable redistributing the > software (or preprocessed details), but if you're really interested > you could obtain it directly yourself. Sorry, I'm not interested enough to register at this time. :-) I merely tried to be helpful in debugging the issue. > Apparently this API is a good test case for pushing some of the limits > of Boost.Python. Since you agree that this is probably a compiler > issue, it's unlikely that you or anyone else would be able to > reproduce the same errors anyway. The only compiler issue I mentioned was a misleading error message. I still believe the real issue might be inside boost.python (where some code may not support your high arity, and can't be configured with BOOST_PYTHON_MAX_ARITY), but I lack details to be able to confirm this. > I came up with a workaround, which is to wrap a version of the > function without the last three arguments, i.e. from Python I am OK > with always having those last three parameters set to their default > values. But if anyone has any other ideas to try, I'd like to hear them. It would really be best to construct the proverbial "minimal complete test case" that allows others to reproduce the issue. You may consider writing some stand-alone test using similar calls as in your code, which you then may freely send do this list, or file as an issue to the boost tracker. Regards, Stefan -- ...ich hab' noch einen Koffer in Berlin... _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig(a)python.org http://mail.python.org/mailman/listinfo/cplusplus-sig The following line is added for your protection and will be used for analysis if this message is reported as spam: (Raytheon Analysis: IP=82.94.164.166; e-from=cplusplus-sig-bounces+camejia=raytheon.com(a)python.org; from=seefeld(a)sympatico.ca; date=Jun 8, 2009 2:39:33 PM; subject=Re: [C++-sig] g++ compiler limitations other than -ftemplate-depth-n and -DBOOST_PYTHON_MAX_ARITY ?)

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Pybindgen/pygccxml integration
by Ben Fitzpatrick Aug. 20, 2009

Aug. 20, 2009

Hi everyone, I'm just starting to check out pybindgen after the messages I've seen floating around on this mailing list, and I have a question about the pygccxml integration. I've made a pure-virtual class with a pointer return type, like so: class pure_virtual_class { virtual int get_value(int* value)=0; virtual int put_value(int value)=0; static pure_virtual_class* Create(); }; Normally I'd call add_function('get_value', retval(int), [param('int *', 'value', transfer_ownership=True)]) (I think) But since I'm scanning the headers with gccxml, I'm not sure how to tell it to transfer the ownership. Right now it's giving me a TypeConfigurationError during 'parse', which appears to be because it doesn't know how to deal with the ownership. I looked in the documentation and couldn't find anything referencing this, and none of the examples use gccxml. Any ideas? Thanks, Ben Fitzpatrick

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boost::python::str and Python's str and unicode types
by Robert Smallshire Aug. 4, 2009

Aug. 4, 2009

Hello, I'm looking for some confirmation that my understanding of what boost.python is doing is correct. >From what I understand boost::python::str represents the str (PyStringObject) type in Python. Unless I'm missing something, here doesn't seem to be anything like boost::python::unicode representing the unicode type (PyUnicodeObject). Boost.Python does have a built-in conversion from std::wstring to object, but this creates a str in Python, so presumably there is some (lossy?) decoding going on here. It seems that to directly create a PyUnicodeObject from C++ I will need to do one or more of the following: 1) Directly use the Python C API to create and manipulate PyUnicodeObject. 2) Create my own subclass of boost::python::object called for example 'unicode', which would be similar to the str class provided out of the box, but would use PyUnicodeObject underneath and deal with wchar_t rather than char. Correct? Many thanks, Rob DISCLAIMER: This message contains information that may be privileged or confidential and is the property of the Roxar Group. It is intended only for the person to whom it is addressed. If you are not the intended recipient, you are not authorised to read, print, retain, copy, disseminate, distribute, or use this message or any part thereof. If you receive this message in error, please notify the sender immediately and delete all copies of this message.

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boost::python::import crashes when called from a dll
by Sahasranaman MS July 31, 2009

July 31, 2009

I am having a problem. I am running Windows XP, Python 2.5.4. I have a custom library which uses python's urllib2 to download data. The import statement inside the call looks like this: boost::python::object urllib = boost::python::import("urllib2"); This works fine when I use my custom library in an executable application. When I use the library in a dll, while executing, it raises this exception: WindowsError: exception: access violation reading 0x00000008 It is happening exactly at this import statement. I tried importing the 'sys' module first, setting library search path and then run, but its failing to import even the sys module, and fails with the same error. Any advice on how I could fix this? -- Sahasranaman MS

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Using symbols from other python extension modules?
by Hans Meine July 30, 2009

July 30, 2009

Hi, when developing boost::python or SIP-based extension modules, we have repeatedly had the need to use C++ classes or functions from other modules. (E.g. I might have a foocmodule and a corresponding unit test module.) A good use case is a boost::python-like registry (with a slightly different purpose), which should be shared across multiple modules. However, I have always been facing the problem that this seemed to require a common shared library (à la libboost_python), but this is a) overkill e.g. in the case of only a single required function (get_registry()), and b) not supported (AFAIK) by distutils/setuptools (i.e. building shared libraries requires lengthy, possibly non-portable hacks). It would be great if I could somehow tell the dynamic linker to resolve against the function definition in the other module (and in fact it works at least on Linux to link against libfoocmodule.so, but IIRC that's not portable). What are your recommendations/experiences? Thanks, Hans

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Trouble converting numpy.float32 to C++
by Paul F. Kunz July 30, 2009

July 30, 2009

I'm using Boost.Python to wrap a C++ class that takes a std::vector<double> & as argument.. Using scitbx/include/scitbx/boost_python/container_conversions.h as suggested by the Boost.Python FAQ, I can correctly convert and use a Python sequence generated by numpy with numpy.arange(10, dtype=numpy.float64 ) But when I change float64 to float32 I get an exception with message "No registered converter was able to produce a C++ rvalue of type double from this Python object of type numpy.float32" Disappointing but maybe understandable. So I change my C++ class to accept vector <float> and still get exception with "No registered converter was able to produce a C++ rvalue of type float from this Python object of type numpy.float32" ^^^^^ Strange, not the result I expected. Even stranger, if I change the python sequence to float64 while keeping the C++ with vector<float> it works fine; no exception. Any suggestions on how to get numpy.float32 handled? Also numpy.int64 converted to a double.

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