Mailman 3 July 2013 - 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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Exposing a C-style array data member to Python via Boost.Python
by Ashish Sadanandan July 29, 2013

July 29, 2013

I have a struct that contains a C-style array data member. I'd like to have this struct exposed to Python, and this data member be accessible as a tuple in Python. struct S { char arr[10]; }; void foo( S const * ) {} BOOST_PYTHON_MODULE( test ) { using namespace boost::python; class_<S>( "S" ) .def_readwrite( "arr", &S::arr ) ; def( "foo", foo ); } The code above fails to build error C2440: '=' : cannot convert from 'const char [10]' to 'char [10]' C-style arrays are not assignable, so the error makes sense. The code compiles if I change the data member to a plain char instead of an array. I cannot replace the array with an std::array or some other container because the structure is being consumed by a C API. The only solution I can think of is to write a couple of wrappers and do the following 1. A struct S1 that duplicates S except it'll have an std::array instead of a C-style array 2. A foo_wrapper that accepts a S1 const *, copies the contents over to an S instance and calls foo 3. Register a to_python_converter to convert the std::array to a Python tuple This should work, and I'm not too concerned about the data copying at this point, but it'd be nice if I could avoid it and expose the array directly without having to jump through all these hoops. So the question is, how can I expose that C-style array data member to Python as a tuple?

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boosst.python: Unregistering builtins
by serge Guelton July 5, 2013

July 5, 2013

Hi there, I have a small Python function that takes many arguments, perform a few computations then returns. It is called a lot of time and almost all my computations are spent there. Turing it into a C++ function wrapped with boost.python make the whole program run much faster, and a profiling pass informs me that all my time is spent in `rvalue_from_python_stage1'. Digging through the code, it appears that unregistering some intrinsics would make the whole stuff run faster, as the linear search for the right converter would be (hopefully) faster. From what I understand of `registry.cpp` there is no way to undo, control or prevent the registrations made by `initialize_builtin_converters()`. Any tip & trick? cheers

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