Mailman 3 June 2007 - Cplusplus-sig

Re: [C++-sig] Emails to this SIG are not being accepted
by Tom Brooks June 10, 2007

June 10, 2007

> > Hi Tom! > > On Samstag 09 Juni 2007, Tom Brooks wrote: > > I've been trying to ask a question on this SIG for a bit now. Every time > I > > try it, I get an error message! I was wondering if it had to do with it > > having an attachment (2.7mb, .zip file, no .exes inside)? I tried using > a > > new email and subscription. No luck! Here's the error message: > > Certainly you should not post such "monster" files to *any* mailing list. > Just have a look for some free file hoster and post a link here. Hehe, Good point. I'm kinda new to mailing lists, so I forgot that it gets emailed to *everyone*. I'll host it separately next time. I happen to have resolved the issue I was going to ask about, so it's not necessary right now.

1 0

with_custodian_and_ward problem
by Hans Meine June 10, 2007

June 10, 2007

Hi! I have a typical call policies problem, which I believed to be solvable with with_custodian_and_ward, but I cannot get it to compile. (I am using make_constructor, maybe that is relevant?) I guess that I simply did not understand BPL's reference counting policies correctly.. I created a testcase (attached, too): This is my class which internally stores a reference to an object given to the constructor: > struct T > { > T(int &foo) : foo_(foo) {} > int &foo_; > }; > > int someInt; > > static T *createT() > { > return new T(someInt); > } I tried using this export code (and some others), which is obviously wrong: > class_<T, boost::noncopyable>("T", no_init) > .def("__init__", make_constructor( > &createT, > with_custodian_and_ward_postcall<0, 1>())); How can I properly tell BPL to make sure that the object passed to the constructor must not be deleted before the "T" instance? Ciao, / / /--/ / / ANS PS: I am currently using 1.34.0beta, does that matter?

3 3

Emails to this SIG are not being accepted
by Tom Brooks June 9, 2007

June 9, 2007

I've been trying to ask a question on this SIG for a bit now. Every time I try it, I get an error message! I was wondering if it had to do with it having an attachment (2.7mb, .zip file, no .exes inside)? I tried using a new email and subscription. No luck! Here's the error message: This is an automatically generated Delivery Status Notification Delivery to the following recipient failed permanently: c++-sig(a)python.org Technical details of permanent failure: PERM_FAILURE: SMTP Error (state 16): 554 permanent error Any thoughts? I'm just hoping that *this* email goes through.

2 1

Calling a Python function with parameters
by Simon Pickles June 9, 2007

June 9, 2007

Hello, I've now managed to load a python module using boost::python::exec_file() I can extract variables and run functions from C++ too. But I am stumped on how to pass parameters from C++ to a python function. Not much use without that! I'm using boost::python::extract<std::string>(global["pyFunc"]) to run the function, where the python module may be: ##------------------------ def func1(): return "hello from python" pyFunc = func1() ##----------------------------------- The docs don't seem to elaborate on how to add parameters. There is plenty on calling C++ functions from python...... What I want to do is something like this: // C++ answer = extract<std::string>(global["pyFunc(""hi"", ""there"" )"] ## python def pyFunc( str1, str2 ): return str1+str2 Thanks for putting up with a newbie! Simon http://www.simonpickles.com --- http://www.squirtualreality.com _________________________________________________________________ Get a preview of Live Earth, the hottest event this summer - only on MSN http://liveearth.msn.com?source=msntaglineliveearthhm

2 1

Re: [C++-sig] How about class_<...>.enable_copy() ?
by Ralf W. Grosse-Kunstleve June 8, 2007

June 8, 2007

> Oh, and BTW, there is a related thing that bugs me: When I copy.copy() a BPL > exported type with pickling support and __getstate_manages_dict__ set, I get > two objects with *the same* __dict__: Sorry, I didn't foresee this situation. But copying the dict would only push the problem one level down. A deepcopy of the dict could be expensive. Given that you can easily wrap the copy constructor, do you think this needs further attention? If you send me documentation patches I'll review them and check them in. Ralf ____________________________________________________________________________________ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545433

1 0

Re: [C++-sig] How about class_<...>.enable_copy() ?
by Ralf W. Grosse-Kunstleve June 8, 2007

June 8, 2007

> Is there a common short idiom that does that already? Is > there a rationale for not providing copying support? Simply wrap the copy constructor with .def(init<>), e.g.: .def(init<your_type const&>((arg("other")))) Ralf ____________________________________________________________________________________ Fussy? Opinionated? Impossible to please? Perfect. Join Yahoo!'s user panel and lay it on us. http://surveylink.yahoo.com/gmrs/yahoo_panel_invite.asp?a=7

1 0

Re: [C++-sig] Copying objects derived in python from C++?
by Ralf W. Grosse-Kunstleve June 8, 2007

June 8, 2007

This could be connected to missing pickle support. I think copy.copy() essentially pickles/unpickles to make the copy. I'd think if you add pickle support to your class it will work. I'm not sure about the details. See the "pickle suite" docs (link on main Boost.Python page). Ralf ----- Original Message ---- From: Mark Williams <mark(a)image-engine.com> To: c++-sig(a)python.org Sent: Wednesday, June 6, 2007 1:35:26 PM Subject: [C++-sig] Copying objects derived in python from C++? d_copy = copy.copy(d) func(d_copy) ____________________________________________________________________________________ TV dinner still cooling? Check out "Tonight's Picks" on Yahoo! TV. http://tv.yahoo.com/

3 3

Re: [C++-sig] Better introspection/apidoc extraction support?
by Ralf W. Grosse-Kunstleve June 7, 2007

June 7, 2007

> Would it make sense to just add two \n instead of one in > libs/python/src/object/function.cpp:510? I've just checked in a modified version of your patch (and the many required changes to the unit tests...). The changes are in the cvs head only. If you lobby the release manager for backporting to 1.34 I could easily do that, too. (But I'm not sure if this makes sense or not; I'm out of touch with the release plans.) Ralf ____________________________________________________________________________________ Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545433

4 3

Copying objects derived in python from C++?
by Mark Williams June 6, 2007

June 6, 2007

I have a short example below which demonstrates and issue I'm having. I have a base class, "Base", written in C++ and exposed via boost.python. I have class, "Derived", which is written in Python and derives from the C++ base. In addition, there is a simple C++ function "func" which takes a Base* as an argument. What I'd like to be able to do is take a copy of an instance of the derived class, within Python, and pass it into the C++ function. However, this yields an ArgumentError exception: Boost.Python.ArgumentError: Python argument types in MyModule.func(Derived) did not match C++ signature: func(boost::shared_ptr<Base>) So it would appear that in taking a copy of the instance using Python's "copy.copy", I'm losing the C++ portion of the object. What is the correct way to go about doing this, please? Here's the test case I'm using: ================ C++ ============ struct Base { Base(){} }; typedef boost::shared_ptr<Base> BasePtr; void func( BasePtr b ) { std::cerr << "func(" << b.get() << ")" << std::endl; } BOOST_PYTHON_MODULE(MyModule) { class_<Base, BasePtr>("Base", no_init) .def(init<>()) ; def("func", func); } ================ Python ============ import copy from MyModule import * class Derived(Base): pass b = Base() func(b) d = Derived() func(d) d_copy = copy.copy(d) func(d_copy) ============ Example output ============== func(0x9db3500) func(0x9d76b20) Traceback (most recent call last): File "test.py", line 15, in <module> func(d_copy) Boost.Python.ArgumentError: Python argument types in MyModule.func(Derived) did not match C++ signature: func(boost::shared_ptr<Base>) Thanks in advance, Mark

1 0

[c++-sig] How to raise a python exception in boost.python?
by 甜瓜 June 6, 2007

June 6, 2007

I have read the python C API manual for exception handling. It seems that if the function below is called, python interpreter will get a ValueError exception, PyObject* RaiseValueError(PyObject*) { PyErr_SetString(PyExc_ValueError, "for some reason..."); return 0; } just like the statement in python: >>> raise ValueError("for some reason...") Is that right?? Ok, but if I move this function into boost.python, the exception disappeared. object RaiseValueError(object) { PyErr_SetString(PyExc_ValueError, "for some reason..."); return object(); } If I throw a C++ exception, later on the boundary of boost.python, it will be translated into a python exception: (in boost file errors.cpp) BOOST_PYTHON_DECL bool handle_exception_impl(function0<void> f) { try { if (detail::exception_handler::chain) return detail::exception_handler::chain->handle(f); f(); return false; } catch(const boost::python::error_already_set&) { // The python error reporting has already been handled. } catch(const std::bad_alloc&) { PyErr_NoMemory(); } catch(const bad_numeric_cast& x) { PyErr_SetString(PyExc_OverflowError, x.what()); } catch(const std::out_of_range& x) { PyErr_SetString(PyExc_IndexError, x.what()); } catch(const std::exception& x) { PyErr_SetString(PyExc_RuntimeError, x.what()); } catch(...) { PyErr_SetString(PyExc_RuntimeError, "unidentifiable C++ exception"); } return true; } So, I'm really confused. Why does NOT my calling to PyErr_SetString work, while boost.python similar calling works? Does boost.python eats my error flags? Anyway, my goal is the raise a python exception (eg: ValueError) from boost.python based code. How to do that? (Do not tell me to write a custom exception translator and plug it into boost.python... -_-!! The only thing I need is just to raise a python exception directly.) Thank you. --- ShenLei

1 1