Mailman 3 December 2009 - Cplusplus-sig

Trying to implement subscriptable type in c++.
by Anita A Dec. 23, 2009

Dec. 23, 2009

Hi all, I am trying to implement a subscriptable type in c++ (equivalent to python dict), but I get a 'type is unsubscriptable' error. Here is a minimal code sample I tried: -------------------------------------------------------------------------- #include <Python.h> #include <iostream> #include "pyerror.hpp" ///////////////////////////////////////////////////////// PyObject* getitem(PyObject* self, PyObject* args) { std::cout << "getitem" << std::endl; return PyString_FromString("this is an item"); } PyMethodDef method[] = { {"__getitem__", &getitem, METH_VARARGS, ""}, {0, 0, 0, 0} }; static PyMethodDef module_methods[] = { { 0, 0, 0, 0 } }; struct MyObject { PyObject_HEAD }; extern const char* code; int main(int argc, char *argv[]) { Py_InitializeEx(0); PyObject* myModule = Py_InitModule3("test", module_methods, "test module"); assert(myModule); PyTypeObject myType; memset(&myType, 0, sizeof(PyTypeObject)); myType.tp_name = "myType"; myType.tp_basicsize = sizeof(MyObject); myType.tp_methods = method; if (PyType_Ready(&myType) < 0) { std::cout << "type error" << std::endl; return 1; } PyModule_AddObject(myModule, myType.tp_name, (PyObject*)&myType); PyObject* m = PyImport_AddModule("__main__"); PyObject* d = PyModule_GetDict(m); MyObject* odef = PyObject_New(MyObject, &myType); PyDict_SetItemString(d, "obj", (PyObject*)odef); PyObject* rv = PyRun_String(code, Py_file_input, d, d); if(rv == 0) { std::cout << "run error" << std::endl; printException(); return 1; } Py_Finalize(); std::cout << "Done.\n"; return 0; } const char* code = "print dir(obj)\n" "x = obj.__getitem__(1)\n" "print 'direct call:', x\n" "x = obj[1]\n" ; -------------------------------------------------------------------------- Compile and run session. -------------------------------------------------------------------------- $ g++ -I/usr/include/python2.6 pymin.cpp -lpython2.6 $ ./a.out ['__class__', '__delattr__', '__doc__', '__format__', '__getattribute__', '__getitem__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__'] getitem direct call: this is an item run error Error in execution: Traceback (most recent call last): line 4, in ?? <type 'exceptions.TypeError'>: 'myType' object is unsubscriptable -------------------------------------------------------------------------- As you can see, when I call __getitem__() directly, it works, but when I call it as a subscriptable object, I get an error. What am I missing? A simple python equivalent class works as expected: -------------------------------------------------------------------------- class Testi: def __getitem__(self, idx): return 10 if __name__ == '__main__': x = Testi() print dir(x) print x['a'] -------------------------------------------------------------------------- Run session. -------------------------------------------------------------------------- $ python tst.py ['__doc__', '__getitem__', '__module__'] 10 -------------------------------------------------------------------------- I had tried using the PyMappingMethods structure as documented, but there is apparently no way to implement the __contains__() method, that is, to check if a key is present in the dict. Any help would be appreciated.

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[Py++] Include additional code with ctypes code generator
by Nikolaus Rath Dec. 22, 2009

Dec. 22, 2009

Hello, Is there a way to add additional code to the output generated by the ctypes code generator? Specifically, I would like to add some special comments to prevent the autogenerated files being checked by PyLink and PyDev. http://language-binding.net/pyplusplus/documentation/inserting_code.html talks about a add_registration_code method, but it doesn't seem to exist for the ctypes generator: mb = ctypes_module_builder_t( [header_file], symbols_file, gccxml_config=gccxml_cfg ) mb.build_code_creator(shared_library_file) mb.add_registration_code( '#@PyDevCodeAnalysisIgnore', False ) yields AttributeError: 'ctypes_module_builder_t' object has no attribute 'add_registration_code' Best, -Nikolaus -- »Time flies like an arrow, fruit flies like a Banana.« PGP fingerprint: 5B93 61F8 4EA2 E279 ABF6 02CF A9AD B7F8 AE4E 425C

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ANN: PyBindGen 0.13 released
by Gustavo Carneiro Dec. 21, 2009

Dec. 21, 2009

PyBindGen is a Python module that is geared to generating C/C++ code that binds a C/C++ library for Python. It does so without extensive use of either C++ templates or C pre-processor macros. It has modular handling of C/C++ types, and can be easily extended with Python plugins. The generated code is almost as clean as what a human programmer would write. It can be downloaded from: http://code.google.com/p/pybindgen/ Bug reports should be filed here: https://bugs.launchpad.net/ <https://bugs.launchpad.net/pybindgen> pybindgen <https://bugs.launchpad.net/pybindgen> <https://bugs.launchpad.net/pybindgen>Documentation: http://packages.python.org/PyBindGen/ NEWS: - Lots of small bug fixes - Custodian/ward-style memory management works better now - Add 'reference_existing_object' and 'return_interal_reference' options for pointer/reference return values - New Sphinx based documentation -- Gustavo J. A. M. Carneiro INESC Porto, Telecommunications and Multimedia Unit "The universe is always one step beyond logic." -- Frank Herbert

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Re: [C++-sig] Implementation of proper overload resolution
by Hans Meine Dec. 21, 2009

Dec. 21, 2009

Am Freitag, 18. Dezember 2009 16:08:24 schrieb Gustavo Carneiro: > Don't you think that when these overloading problems become an issue it is > a sign of a poorly designed API? I mean, if overloaded functions > parameters are not completely different in type or number, then maybe they > are already too confusing to use and should not be overloaded in the first > place?... No, in C++ overloading rules are (quite) well-specified and everybody's used to them. In python, overloading is absent. Now python bindings of C++ libraries are supposed to mimick C++'s overloading, and AFAICS Troy did great work in order to let the BPL be better at this, i.e. more closely follow the rules of C++ w.r.t. overload resolution. (Previously, BPL's first[/last]- come-first-serve rule would not match people's expectations in many cases.) Ciao, / / /--/ / / ANS

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Re: [C++-sig] what do I need to correctly port boost python extensions
by Hans Meine Dec. 21, 2009

Dec. 21, 2009

Hi Am Montag, 14. Dezember 2009 23:09:31 schrieb Nikolaus Rath: > Alexey Akimov <alexey.akimov85(a)gmail.com> writes: > > However I am still wondering if there is a way to avoid rebuilding the > > extension when one travel from machine to machine. > > The only way is to have exactly the same runtime environment (i.e., > having installed the same distributions with the same version on the > same architecture). Otherwise you have to recompile. I think you're a bit too pessimistic. While I agree that the "normal"/standard way on Linux(*) is to recompile for a specific distribution / machine type, there is the LSB standard which makes certain distributions "similar enough" so that your binary might work. Read: You could try an existing binary before recompiling, when the machines are not too different. Ciao, / / /--/ / / ANS *: OK, there is proprietary, closed-source software which is usualy distributed together with most dependencies, either statically linked or with a bit .so collection and some shell script / LD_LIBRARY_PATH startup magic.

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interrupting long running c++ code
by Neal Becker Dec. 20, 2009

Dec. 20, 2009

I don't suppose there's any way to allow interrupt signal through while a long-running boost::python wrapped function is running? It seems that python blocks the signal until the function completes. This is a single-threaded environment.

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PyThreadState_Get: no current thread
by Charles Solar Dec. 19, 2009

Dec. 19, 2009

Its getting kind of late and my eyes are getting tired so I wanted to throw up this problem I am having and see if I can get some feedback on what might be going wrong here. I built boost::python into my app and exported a bunch of stuff. All is well when I just call functions and do not much at all (the example apps all work for example). However, when I start actually trying to use the features of my library I crash python. In debug mode I get a ton of "PyThreadState_Get: no current thread" messages printed before it crashes from what I assume is a stack overflow. In release mode it just crashes. Both crash while executing Py_ALLOW_RECURSION t = PyDict_GetItem(interned, (PyObject *)s); Py_END_ALLOW_RECURSION in unicodeobject.c line 9725 The stack trace once the program enters the python dll looks like this (going bottom to up) python31_d.dll!Py_FatalError(const char * msg=0x000007fef0c350f8) Line 2013 + 0x5 bytes C python31_d.dll!PyThreadState_Get() Line 351 C python31_d.dll!PyErr_Occurred() Line 133 + 0x5 bytes C python31_d.dll!Py_FatalError(const char * msg=0x000007fef0c350f8) Line 2013 + 0x5 bytes C python31_d.dll!PyThreadState_Get() Line 351 C python31_d.dll!PyUnicode_InternInPlace(_object * * p=0x000000000330ef18) Line 9725 + 0x5 bytes C python31_d.dll!PyUnicode_InternFromString(const char * cp=0x000007fef113ef28) Line 9766 C python31_d.dll!PyObject_GetAttrString(_object * v=0x000000000245f658, const char * name=0x000007fef113ef28) Line 751 + 0xa bytes C i have a suspicion about what may be causing this error but I am afraid I do not know enough about python to know for sure, so here where you guys come in :) My program ( that python is controlling ) is multithreaded. I am thinking that one of the other program threads is calling a python method and that is what is causing this crash. I am using the observer pattern in my design and I have a python object that I attach to an object to watch for changes. When the object is changed, my python code should get executed. The notify method to tell all the observers there was a change could get called from a separate thread. I am pretty sure I have wrapped the classes and definitions correctly to allow this to happen thanks to the boost::python doc. So my question is, would calling python code from a thread other than the main thread cause this problem? And if so, how can I fix this? Thank you for your time

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[Py++] Generate Python code for ctypes?
by Nikolaus Rath Dec. 16, 2009

Dec. 16, 2009

Hello, Is it possible to use Py++ to "convert" structures from a C header, say ,---- | struct flock | { | short int l_type; /* Type of lock: F_RDLCK, F_WRLCK, or F_UNLCK. */ | short int l_whence; /* Where `l_start' is relative to (like `lseek'). */ | #ifndef __USE_FILE_OFFSET64 | __off_t l_start; /* Offset where the lock begins. */ | __off_t l_len; /* Size of the locked area; zero means until EOF. */ | #else | __off64_t l_start; /* Offset where the lock begins. */ | __off64_t l_len; /* Size of the locked area; zero means until EOF. */ | #endif | __pid_t l_pid; /* Process holding the lock. */ | }; `---- from fcntl.h into the corresponding ctypes Structure, ,---- | class flock_t(Structure): | _fields_ = [ | ('l_type', c_short), | ('l_whence', c_short), | ('l_start', c_uint64), | ('l_len', c_uint64), | ('l_pid', c_int) | ] `---- while automatically taking into account the #ifdefs and how types like off_t and pid_t are actually defined on the target system? The introduction on http://www.language-binding.net/pyplusplus/pyplusplus.html says that Py++ can act as a code generator for ctypes, but I could not find any documentation for the sort of application that I describe here. Best, -Nikolaus -- »Time flies like an arrow, fruit flies like a Banana.« PGP fingerprint: 5B93 61F8 4EA2 E279 ABF6 02CF A9AD B7F8 AE4E 425C

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Re: [C++-sig] [Py++] Missing struct
by Roman Yakovenko Dec. 15, 2009

Dec. 15, 2009

On Tue, Dec 15, 2009 at 6:12 PM, Nikolaus Rath <Nikolaus(a)rath.org> wrote: >> Can you create a small example, which reproduce the problem and send it to me? > > The attached file should reproduce the problem, but it needs the fuse > headers to be installed (Debian/Ubuntu: libfuse-dev). Let me know if > you don't have them/don't want to install them, then I'll come up with > my own header instead. Okey. That helped. The problem was in pygccxml - it didn't calculate right a struct dependencies in case of variables. To be more specific, fuse structs contains variables, which are pointers to functions and pygccxml failed in this case. I committed the fix. You will need to update pygccxml and Py++ projects. I also attached the generated file. -- Roman Yakovenko C++ Python language binding http://www.language-binding.net/

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Boost Python - How to export boost::shared_ptr<std::string>
by Romain CHANU Dec. 15, 2009

Dec. 15, 2009

Hi, I want to export an attribute which is a boost::shared_ptr<std::string> and I got the following error: " TypeError: No Python class registered for C++ class class boost::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > " I found an old post on a similar issue : http://old.nabble.com/Boost.python---How-to-export-shared_ptr%3Cvector%3Csh… no one has replied :-\ Can anyone tell me how can I export this type? Thank you! Romain

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