Mailman 3 December 2009 - Cplusplus-sig

what do I need to correctly port boost python extensions
by Alexey Akimov Dec. 14, 2009

Dec. 14, 2009

Hello to everyone, I get confused trying to port my boost python extension module. So I've made a shared object file test.so which actually perfectly works in the original development directory. However, when I copy this file to another Linux machine (I also copy some extra libraries such as libboost_python-gcc344-1_39.so.1.39.0 and make sure that both .so files are in PATH and LD_LIBRARY_PATH) I recieve "Import Error: undefined symbol: /home/username/bin/libboost_python-gcc34-1_39.so.1.39.0: PyUnicodeUCS4_FromEncodedObject". I aslo istalled the same version (compared to one which was used for creation of the module) of Python to the Linux machine where I try to use my extension. Can anyone explain me where could the problem be. Also I would clarify what is the general way to export just created modules? As I understand the order is following: 1) create .so object (look for it in /bin/compiler-name/release-or-debug/module-name.so directory) 2) copy this file as well as other necessary library to some /bin or /lib directory (for convenience) - and make sure they are in PATH and LD_LIBRARY_PATH variables. 3) import the module in python interpreter. Do I need to do something else (define some other variables or make some other changes) in order to make my module work? Thanks a lot Alexey

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extracting a numpy.int32 type
by Nathan Huesken Dec. 11, 2009

Dec. 11, 2009

Hi, I have something like this in my code: void function(numeric::array& ids) { ... int x=extract<int>(ids[make_tuple(pos)]); ... } Now I plug in a numpy arra with dtype=np.int32. I get: No registered converter was able to produce a C++ rvalue of type int from this Python object of type numpy.int32 It also happens for numpy.int64. But if I extract i.E. a double from a numpy.float64 array, it works. What can I do here? Thanks! Nathan

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Re: [C++-sig] errors with multiple loading cryptopp as shared lib on Linux
by Zooko O'Whielacronx Dec. 10, 2009

Dec. 10, 2009

[cross-posted to the Crypto++ users mailing list and the Python C++-sig.] David wrote on the Crypto++ users mailing list: > We experience errors when trying to use cryptopp as shared lib from more than one other shared libs. I struggled with this for a long time for the pycryptopp project and finally gave up and just refactored pycryptopp so that there is only one sharedlib that links to libcryptopp.so. It kind of sucks because this means that if some *other* library gets loaded into the same process as pycryptopp and that library links to libcryptopp.so then it will crash the process. But, I couldn't figure out any other way to solve it. Here is a letter I wrote at the time outlining four possible solutions. I tried them all and ended up using the one listed as "#2": http://mail.python.org/pipermail/cplusplus-sig/2009-May/014531.html I still kind of hope that some Crypto++ or Python hackers will figure out how to implement the one listed as "#4", which is to mark the appropriate symbols in the Crypto++ API as being satisfied by a different DSO (mark them as 'U' -- undefined symbols) so that the loader will do the right thing. See the end of that letter referenced above for details. It kind of seems like gcc cannot be configured to do the right thing here, although MSVC can. Here is an earlier letter I wrote explaining how there are two different problems, one that happens if you set RTLD_GLOBAL and one that happens if you don't set RTLD_GLOBAL: http://groups.google.com/group/cryptopp-users/msg/7a0dacd0a4be5e2d Here is the ticket that we used to track this issue in pycryptopp until it was solved by the "there can be only one user of libcryptopp.so" solution: http://allmydata.org/trac/pycryptopp/ticket/9 Regards, Zooko

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export class constant
by Gennadiy Rozental Dec. 10, 2009

Dec. 10, 2009

Hi, Let's say I have string literal as static C++ class member: string Foo::abc = "ABC"; I'm exporting the class Foo. I'd like to export Foo::abc as well and be able to access it on Python side using similar interface: Foo.abc. Can I do this using Boost.Python? Gennadiy

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Python C++ extension (multi threaded) raises access violation exception
by Jadhav, Alok Dec. 8, 2009

Dec. 8, 2009

I am using SWIG to extend Python to C++. But the questions I have consists of basic Python C API related. I hope this list will be able to help me. I am trying to solve a simple problem which many of you must have encountered. I wonder what I am doing different than others that I am facing a problem. Background ----------- A c++ library is wrapped in my C++ Class. This new C++ class is extended in Python using SWIG. I have to call a python function from C++ code ( which is on a new thread spawned from C++ main thread). Issue ----- I am able to call the function. No issues. I could pass basic data types such as int. No issues. But when I try to pass a C++ class object (eg RFAMessageWrapper) to my python function I get an exception. It is an Access violation exception. The memory could not be "read". I am not even able to catch this exception. Some code snippets -------------------- C++ function which calls python function. ... [code] static void PythonCallBack(RFAMessage *msg, void *clientdata) { PyObject *func, *arglist; int blah = 1; PyGILState_STATE state; state = PyGILState_Ensure(); func = (PyObject *) clientdata; // Get Python function RFAMessageWrapper msg2(msg); try { arglist = Py_BuildValue("(O)",msg2); // Build argument list //arglist = Py_BuildValue("(i)", blah); PyEval_CallObject(func,arglist); // Call Python } catch (...) { cout<<"Unknown exception..."<<endl; } Py_XDECREF(arglist); // Trash arglist PyGILState_Release(state); } [/code] Python function call.. [code] def callback_fun(msg): try: print "RFAMessage received for service:"+msg.service except Exception: print "Exception handled" [/code] Whenever I try to access msg (of type RFAMessageWrapper .. C++ object) I get exception. msg is not None. I checked that in if condition. even type(msg) raises exception. RFAMessageWrapper class has been wrapped properly by SWIG as I could create an object manually and use it in Python. But only when I pass it from C++ to python I get this exception. I have spent long time to solve this issue but in vain. I hope I get some help from this Forum. Regards, Alok =============================================================================== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html ===============================================================================

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Re: [C++-sig] Cplusplus-sig Digest, Vol 15, Issue 3
by meiko rachimow Dec. 7, 2009

Dec. 7, 2009

when i: "fun(**kwargs)" I get following runtime error: TypeError: No to_python (by-value) converter found for C++ type: boost::python::detail::kwds_proxy thx again meiko > Message: 1 > Date: Thu, 3 Dec 2009 13:11:41 +0100 > From: meiko rachimow <rachimow(a)googlemail.com> > To: cplusplus-sig(a)python.org > Subject: [C++-sig] boost.python: call python function with kwargs from > c++ > Message-ID: > <6a5b23630912030411m5be57968t9d8a2a7baf43fb9c(a)mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > Hi > > How can I call a function defined in a python module from c++, > if I have to give **kwargs parameter... > > example.py: > > def hello(**kwargs): > for key, value in kwargs.items(): > print key, " - ", value > > > c++: > using namespace boost::python; > > object fun = import("example").attr("hello") > fun() > > int number = 42 > std::wstring name = "M?hre" > > dict kwargs; > kwargs["Number"] = number; > kwargs["Name"] = name; > > fun(...) ??? > > What should i do ? > > Meiko >

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functools.partial vs boost::python
by Neal Becker Dec. 4, 2009

Dec. 4, 2009

Has anyone noticed that a function created with boost::python using args() to give keyword arguments doesn't seem to work with functools.partial keyword arguments (but does with positional args)? For example, I have this function: class_<boost_uniform_real_wrap> ("uniform_real", "Uniform float distribution", bp::init<rng_t&,double,double>( (bp::arg ("rng"), bp::arg ("min"), bp::arg ("max"))... Then: from functools import partial f = partial (uniform_real, rng=rng1) << using keyword doesn't work f (1,2) ArgumentError: Python argument types in uniform_real.__init__(uniform_real, int, int) did not match C++ signature: __init__(_object*, boost::random::mersenne_twister<unsigned int, 32, 624, 397, 31, 2567483615u, 11, 7, 2636928640u, 15, 4022730752u, 18, 3346425566u> {lvalue} rng, double min, double max) But this works: from functools import partial f = partial (uniform_real, rng1) << pos arg does work In [27]: f(1,2) Out[27]: uniform_real(1,2)

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boost.python: call python function with kwargs from c++
by meiko rachimow Dec. 3, 2009

Dec. 3, 2009

Hi How can I call a function defined in a python module from c++, if I have to give **kwargs parameter... example.py: def hello(**kwargs): for key, value in kwargs.items(): print key, " - ", value c++: using namespace boost::python; object fun = import("example").attr("hello") fun() int number = 42 std::wstring name = "Möhre" dict kwargs; kwargs["Number"] = number; kwargs["Name"] = name; fun(...) ??? What should i do ? Meiko

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