Mailman 3 June 2005 - Cplusplus-sig

basic embedded boost.python build question
by Nathan Tuck June 30, 2005

June 30, 2005

I have a somewhat basic build question for embedded python, but I have not been able to google the answer. First of all, I am using Linux. I want to build an application with an embedded (dynamically linked) python interpreter and a module of statically linked (into the application executable) boost.python routines. I would prefer not to compile separate .so's for the modules or include my own custom version of the interpreter. Is it possible to make this work? The best solution I have come up with so far has three pieces: 1) an executable 2) the boost module .so and 3) another .so implementing the functions that are called both by the boost module and the executable. Surely there is a way I can get this down to one file (just the executable) which dynamically links to the main python libs? Thanks, Nathan

2 1

str operator
by Ult Mundane June 29, 2005

June 29, 2005

Hi there, I'm having trouble getting the str operator to compile. Any help would be greatly appreciated! I'm building on linux with gcc. Here's my example code: --- foo.cpp -- #include <iostream> #include <boost/python.hpp> using namespace boost::python; using namespace std; class Foo { public: int val; }; ostream & operator<<(ostream & output, Foo const & f) { return output << f.val; }; BOOST_PYTHON_MODULE(foo) { class_<Foo>("Foo", init<>()) .def(str(self)) ; } --- end foo.cpp --- And here's my compile error: g++ -fPIC -Iboopy/src/foo -Ilibs/boost-1.32.0/src/python/src -Ilibs/boost-1.32.0/include -Ilibs/python-2.2/include -Ilibs/python-2.2/include/linux-i686 -c -o linux-i686-boopy/boopy/src/foo/foo.os boopy/src/foo/foo.cpp libs/boost-1.32.0/include/boost/python/def_visitor.hpp: In static member function `static void boost::python::def_visitor_access::visit(const V&, classT&) [with V = boost::python::def_visitor<boost::python::api::object>, classT = boost::python::class_<Foo, boost::python::detail::not_specified, boost::python::detail::not_specified, boost::python::detail::not_specified>]': libs/boost-1.32.0/include/boost/python/def_visitor.hpp:67: instantiated from `void boost::python::def_visitor<DerivedVisitor>::visit(classT&) const [with classT = boost::python::class_<Foo, boost::python::detail::not_specified, boost::python::detail::not_specified, boost::python::detail::not_specified>, DerivedVisitor = boost::python::api::object]' libs/boost-1.32.0/include/boost/python/class.hpp:225: instantiated from `boost::python::class_<T, X1, X2, X3>& boost::python::class_<T, X1, X2, X3>::def(const boost::python::def_visitor<Derived>&) [with Derived = boost::python::api::object, W = Foo, X1 = boost::python::detail::not_specified, X2 = boost::python::detail::not_specified, X3 = boost::python::detail::not_specified]' boopy/src/foo/foo.cpp:22: instantiated from here libs/boost-1.32.0/include/boost/python/def_visitor.hpp:31: no matching function for call to `boost::python::api::object::visit(boost::python::class_<Foo, boost::python::detail::not_specified, boost::python::detail::not_specified, boost::python::detail::not_specified>&) const'

4 3

Wrapping classical C API for python access
by Markus Schöpflin June 28, 2005

June 28, 2005

I'm currently in the process of evaluating how feasible it would be to use boost.python to expose a classical C API to python. By classical C API I mean that most arguments are passed around as pointers (both in and out), and nearly every function has an int return value for the error code. How do I deal with functions using pointers as out parameters? Given, for example, the function "int test(char const *s, int *p)" where p is an out parameter, I can easily wrap it with BP using test("foo", foo). But when trying to call this function from python, I keep getting the following error: >>> a = int(0) >>> print test("foo", a) Traceback (most recent call last): File "<stdin>", line 1, in ? Boost.Python.ArgumentError: Python argument types in pyubss.test(str, int) did not match C++ signature: test(char*, int*) So how do I specify that p is an out parameter? How do I have to call the function in Python? Is it possible? TIA, Markus

4 10

double vs float in Py_BuildValue
by Gary Robinson June 27, 2005

June 27, 2005

I'm having a problem I think is fairly bizarre using Py_BuildValue (note, this code isn't presently using boost.python, it's the straight Python-C interface). Here's an example c module: > #include <Python.h> > static float gfSumChiSquare = 0.0; > > > static PyObject * > getSumChiSquare(PyObject *self, PyObject *args){ > return Py_BuildValue("f", gfSumChiSquare); > } > > static PyMethodDef SimMethods[] = { > {"getSumChiSquare", getSumChiSquare, METH_NOARGS, "Return > fSumChiSquare"}, > {NULL, NULL, 0, NULL} /* Sentinel */ > }; > > PyMODINIT_FUNC > inittestfloat(void) > { > (void) Py_InitModule("testfloat", SimMethods); > } > > If the float, gfSumChiSquare, is defined as a float, as above, it works fine. But if I turn it into a double: static double gfSumChiSquare = 0.0; ... static PyObject * getSumChiSquare(PyObject *self, PyObject *args){ return Py_BuildValue("d", gfSumChiSquare); } ... I get a bus error when I call it from Python. I'm extremely rusty in C, not having used it in about 7 years, so maybe that's what's responsible. But I would appreciate some insight here! As always, in appreciation the help I find in this sig, Gary

2 4

Embedding: Creating a Python object with BPL
by Jan Heiser June 27, 2005

June 27, 2005

Hi, I need to create a Python object (that is completely defined in a python module) from C++. I can import the module, find the class object and (in other routines) can access the data and methods of objects. I can even use the class object to check the validity of objects (using PyObject_IsInstance). However, I did not find a way to create a new object based on this class object. Is there a way with BPL to call the class' constructor somehow? Failing that, how can one do that using the Python C-API? I can only find constructors for basic types in there. There is Py_ObjectNew() but that does take a PyTypeObject* which I don't have (can I get it from the class object?). Furthermore, I don't see a way to specify constructor arguments in the call. Jan. -- <jan.heiser(a)raubtierbaendiger.de>

2 2

Boost tutorial Jamfile discrepancy
by Gary Robinson June 26, 2005

June 26, 2005

http://www.boost.org/libs/python/doc/tutorial/doc/html/python/hello.html says that the Jamfile for hello.cpp is subproject libs/python/example/tutorial ; SEARCH on python.jam = $(BOOST_BUILD_PATH) ; include python.jam ; extension hello # Declare a Python extension called hello : hello.cpp # source <dll>../../build/boost_python # dependencies ; However the actual contents are: # Hello World Example from the tutorial # [Joel de Guzman 10/9/2002] # Specify our location in the boost project hierarchy subproject libs/python/example/tutorial ; # Include definitions needed for Python modules import python ; extension hello # Declare a Python extension called hello : hello.cpp # source <dll>../../build/boost_python # dependencies ; They are quite different -- which is correct? Gary

4 3

OS X boost.python tutorial question
by Gary Robinson June 26, 2005

June 26, 2005

>> The remaining mystery is that the tutorial docs say that >> libboost_python.so should have been produced, but in fact >> libboost_python.pylib was produced. >> > (http://www.boost.org/libs/python/doc/tutorial/doc/html/python/hello.html). >> I'm not sure if the docs are wrong or if I'm missing something. > > The docs were written for every other *nix system on the planet ;-) > Apple decided to make up their own extension for dynamic libraries, so > it doesn't quite fit. Er.... obviously I meant libboost_python.dylib, not .pylib. I read through the Apple docs on finding dynamically-linked libraries and I now understand why it couldn't find the dylib originally and why it could when I set DYLD_LIBRARY_PATH. BUT I don't understand why it originally tried to find it at a relative path that was not where the file was. Is that due to an incompatibility between OS X and other Unixes, or is there an error in the tutorial code, or was there no way to make it work "out of the box" when hello.so is loaded, or is there something else I'm missing? Gary

1 0

OS X boost.python tutorial question
by Gary Robinson June 26, 2005

June 26, 2005

> > Do you have the directory > /Users/garyrob/Desktop/boost_1_32_0/bin/boost/libs/python/build/libboost_python.dylib/darwin/release/shared-linkable-true > in your $DYLD_LIBRARY_PATH environment variable? No, I didn't -- and in fact I never heard of DYLD_LIBRARY_PATH before. I am truly a newbie. A complete newbie to boost, but 99.5% a newbie to unix development as well. Thanks for the tip! But the thing that made it counterintuitive to me that to think that it might be a matter of the path is the fact that when I tried to import hello it told me it couldn't load the libboost_python.dylib file, and the error message named the exact location where it really was. If it knows exactly where it is, why does it need an environment variable with the path? I guess DYLD_LIBRARY_PATH must "bless" the directories it lists to make their contents OK for use as dynamic libraries? Dunno. I found some docs on it on Apple's site and will read about it. The remaining mystery is that the tutorial docs say that libboost_python.so should have been produced, but in fact libboost_python.pylib was produced. (http://www.boost.org/libs/python/doc/tutorial/doc/html/python/hello.html). I'm not sure if the docs are wrong or if I'm missing something. Gary -- Gary Robinson CEO Transpose, LLC grobinson(a)transpose.com 207-942-3463 Company: http://transpose.com Blog: http://www.garyrobinson.net

2 1

Re: [C++-sig] OS X boost.python tutorial question
by Gary Robinson June 25, 2005

June 25, 2005

>> Some of this is a repeat of an early question, but I really need an >> answer if one is available to be had. We want to use boost.py in our >> product, Goombah (http://www.python.com). ... Er... I meant http://www.goombah.com... www.python.com is a "notorious porn site," Tim Peters informs me... guess my fingers weren't paying much attention to my brain... Gary

1 0

OS X boost.python tutorial question
by Gary Robinson June 25, 2005

June 25, 2005

Some of this is a repeat of an early question, but I really need an answer if one is available to be had. We want to use boost.py in our product, Goombah (http://www.python.com). We have it working on Windows, and have C code working in the product that uses boost.python on Windows. But we need it to work on OS X too if we're going to use it, since Goombah is a cross-platform product. I have built boost.python successfully (at least it gives no "failure" or "skipped" messages). I did it by going to the root boost directory and entering: bjam "-sPYTHON_ROOT=/System/Library/Frameworks/Python.framework/Versions/2.3" "-sPYTHON_VERSION=2.3" "-sTOOLS=darwin" "-sBUILD=debug release" I then went to the ../examples/tutorial folder and ran bjam with the same arguments, and that too seemed to complete successfully. hello.so was created and was in the directory /Users/garyrob/Desktop/boost_1_32_0/bin/boost/libs/python/example/tutorial/hello .so/darwin/release/shared-linkable-true/hello.so However the tutorial text explicitly states that libboost_python.so will be created too. No such file was created. I don't know whether the it's the documentation that's in error or whether something didn't work right in the build. Can someone tell me which is the case? When I enter interactive python and try to import the hello module, I get: import hello Traceback (most recent call last): File "<stdin>", line 1, in ? ImportError: Failure linking new module: ../../../bin/boost/libs/python/build/libboost_python.dylib/darwin/release/shared -linkable-true/libboost_python.dylib: dyld: python can't open library: ../../../bin/boost/libs/python/build/libboost_python.dylib/darwin/release/shared -linkable-true/libboost_python.dylib (No such file or directory, errno = 2) libboost_python.dylib was created, and is in the stated location (if ../../.. means ~/Desktop/boost_1_32_0/ on my machine). So I don't know why it's giving me an error: ls -l ~/Desktop/boost_1_32_0/bin/boost/libs/python/build/libboost_python.dylib/darwin/ release/shared-linkable-true/libboost_python.dylib -rwxr-xr-x 1 root staff 1102392 24 Jun 09:53 /Users/garyrob/Desktop/boost_1_32_0/bin/boost/libs/python/build/libboost_python. dylib/darwin/release/shared-linkable-true/libboost_python.dylib Gary-Robinsons-Computer:~/Desktop/boost_1_32_0/bin/boost/libs/python/example/ tutorial/hello.so/darwin/release/shared-linkable-true garyrob$ If anyone can help me get the tutorial working I'd really appreciate it. Gary

3 2