Mailman 3 February 2006 - Cplusplus-sig

C++ singleton
by Emmanuel Taurel Oct. 31, 2007

Oct. 31, 2007

Hello everybody, I am actually writing an interface to python for an existing C++ library using Boost. This library has a C++ singleton class. This class has only one constructor (with arguments) which is "protected" because it's a singleton. I am not able to build a Boost interface to this class because the compiler complains that the constructor I have given to Boost in the class_xxx constructor argument is not public (which is true) ! Therefore, my question is simple : How is it possible to interface such a class with only one constructor which is protected and a static method to create/access the object ? Thank's very much for your answer. Sincerely Emmanuel Taurel (etaurel(a)cells.es) PS : By the way, is there a searchable archive of this mailing list ?

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optimizing away calls to the python runtime -- was [detecting if a function is written in python or C++]
by Mathieu Lacage May 15, 2006

May 15, 2006

hi, I apologize for this second email but the more I think about what I am trying to do, the less I see how to do it. So, here is a hopefully detailed explanation of what I am trying to achieve. Here are my c++ classes: class Event { virtual void notify (void) = 0; }; class Simulator { void schedule (Event *event); double now_s (void); // return current time. void run (void); }; sample c++ use code: class MyEvent : public Event { virtual void notify (void) { std::cout << "now=" Simulator::now_s () << std::endl; delete this; } }; Simulator->schedule (new MyEvent ()); Simulator->run (); // invokes MyEvent::notify sometime later. This sort of code requires a lot of "forwarding code". That is, you often have to write a bunch of Event-deriving classes whose sole purpose in life is to forward the call to their notify method to a call to another class' method with event-specific parameters. So, I have a small make_event c++ template which can be used to do this sort of thing: class MyClass { void random_stuff (double id) { std::cout << "id="<<id<<"now=" Simulator::now_s () << std::endl; } }; MyClass *obj = new MyClass (); Simulator->schedule (make_event (&MyClass::random_stuff, obj, 10.0)); Simulator->run (); Okay, so, to wrap this, I wrapped my Simulator class and my EventWrap class: struct EventWrap : yans::Event { EventWrap( PyObject* self_); virtual ~EventWrap(); virtual void notify (void); private: PyObject *m_self; }; EventWrap::EventWrap (PyObject* self_) : m_self(self_) { Py_INCREF(m_self); } EventWrap::~EventWrap() { Py_DECREF(m_self); } void EventWrap::notify (void) { call_method<void>(m_self, "notify"); delete this; } namespace boost { namespace python { template <> struct has_back_reference<EventWrap> : mpl::true_ {}; }} void export_event (void) { class_<EventWrap, std::auto_ptr<EventWrap>, boost::noncopyable> event ("Event"); event.def ("notify", pure_virtual(&Event::notify)); } void simu_insert_in_s (double delta, std::auto_ptr<EventWrap> ev) { Simulator::insert_in_s (delta, ev.get ()); ev.release (); } void export_simulator (void) { def ("run", Simulator::run); def ("insert_in_s", simu_insert_in_s); } which allows me to write the following python code: class __MyEvent__(Event): def set_callback (self, function, *args): self.__function_ = function; self.__args_ = args; def notify (self): self.__function_ (*self.__args_); def make_event(function, *args): ev = __MyEvent__ (); ev.set_callback (function, *args); return ev def my_nothing0 (): print "my model now=%f" % simulator.now_s (); simulator.insert_in_s (4.0, make_event (my_nothing1, 99)); simulator.run () okay, so all of this stuff works really nicely but there is a catch. I would like to be able to write code such as: simulator.insert_in_s (4.0, make_event (simulator.now_s)); simulator.run () and ensure that once simulator.run has reached the Simulator::run c++ method, no python code will be executed ever. Namely, I want call to make_event to generate a nice C++ Event class which will not call back into python's __MyEvent__.notify before calling simulator.now_s and Simulator::now_s. i.e., it should call back Simulator::now_s directly. The more I think about this, the less I see a way to do this with boost. Have I missed something ? Mathieu --

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GCC version compatibility
by David Abrahams April 15, 2006

April 15, 2006

The following message is a courtesy copy of an article that has been posted to gmane.comp.python.devel as well. Recently people testing Boost.Python with GCC on Linux have reported that the extensions being tested have to be compiled with exactly the same version of GCC as the Python they're being loaded into, or they get mysterious crashes. That doesn't correspond to my past experience; it has always been true that, as long as the compiler used to build Python and the one used to build the extension have compatible 'C' ABIs, we've been okay. Yes, if you were going to pass types like FILE* across the Python/C API, then you additionally need to be sure that the two compilers are using the same 'C' library. That said, none of the Boost.Python tests do that. I'm wondering if there has been a well-known recent change either in Python or GCC that would account for these new reports. Any relevant information would be appreciated. -- Dave Abrahams Boost Consulting www.boost-consulting.com

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RE: Wrapper for exception translation
by Gottfried.Ganssauge＠HAUFE.DE April 4, 2006

April 4, 2006

> -----Original Message----- > From: David Abrahams [mailto:dave@boost-consulting.com] > Sent: Monday, December 13, 2004 1:04 PM > To: c++-sig(a)python.org; Gottfried Ganßauge > Subject: Re: Wrapper for exception translation > > > Gottfried Ganßauge wrote: > > Hi Dave, > > > > I digged through the class_<> implementation and I think I > know what I > > must do to implement it. Like you suggested I would add another > > argument to the class_base constructor which is used as > another base > > class for the newly created class. > > Hi Gottfried, Hi Dave, > > I don't know if you're still listening, but today I offered to > implement this patch on the C++-sig (see my other post). > Are you still interested? I am still listening but was buried deeply with work so I even had to abandon the work already invested into this. Nonetheless: Yes - I'm still interested. Cheers, Gottfried P.S.: What second Post? I got 2 Copies of this one. > > > > -- > Dave Abrahams > Boost Consulting > http://www.boost-consulting.com >

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ImportError
by Etienne Lachance Feb. 28, 2006

Feb. 28, 2006

Hi All, I'm having a problem when importing my library. I'm using a Makefile to compile my library. Do you know what is the problem? Thanks. Etienne Here is the code: class GA_scalingLinearET { public: GA_scalingLinearET(double dMulFactor = 1.0); void setMultiplicationFactor(double factor); double getMultiplicationFactor() const { return dMulFactor; } private: double dMulFactor; //!< Multiplication factor }; #include <boost/python.hpp> #include "gailGAscaling.h" using namespace boost::python; BOOST_PYTHON_MODULE(gailGA) { class_<GA_scalingLinearET>("GA_scalingLinearET", init<double>()) .def("getMultiplicationFactor", &GA_scalingLinearET::getMultiplicationFactor) ; } >>> import gailGA Traceback (most recent call last): File "<stdin>", line 1, in ? ImportError: ./gailGA.so: undefined symbol: _ZN18GA_scalingLinearETC1Ed

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Patches and complete pyste replacement prototype for pyplusplus
by Allen Bierbaum Feb. 28, 2006

Feb. 28, 2006

While Roman was on vacation I took it upon myself to delve into pygccxml and pyplusplus and give my best shot and creating a user-friendly Pyste replacement on top of these powerful tools. Well after many hours of design, implementation, and refinement I have come up with something that works very well for me. I have used it to wrap a couple of large libraries and it gives me all the features I used to have in Pyste plus a *lot* more capabilities and power thanks to Roman'a great work. I haven't had time yet to provide complete documentation to the new API, but I hope to find some time to do that this weekend. Until then though I wanted to get my changes out for public consumption and review. Roman and Matthias: I have attempted to implement some solution or method for every topic we have talked about so far on the e-mail list. If there was anything I missed please let me know. This API has evolved from my original proposal and thus differs in implementation from the interface Matthais has proposed. I read his proposal though and tried to incorporate the ideas where possible. If I haven't used an idea it is either because I found another way to handle the issue or I found issues with either the use of implementation. Anyway, without further delay here is how to get your hands on the code. First, there are two parts: - A large patch for pygccxml/pyplusplus - A python module providing the user-interface API -------- [ Patches ] ---------- The patches to pygccxml/pyplusplus can be found at: https://realityforge.vrsource.org/view/PyOpenSG/PyPlusPlusCodeChanges README at: https://realityforge.vrsource.org/twiki/pub/PyOpenSG/PyPlusPlusCodeChanges/… There included README has tons of details, but the highlights are: -The goal of the changes contained herein was to allow the creation and use of a user-level API for wrapping pyplusplus with a very simple to use yet powerful interface. - Added verbose flag for additional output: (stage, gccxml cmdline, timing) - Cache refactoring: use md4 hashes, support for temp files, smarter saving and cleaning of cache - Improved detection of gccxml errors - Decl Decorator: I added the decl decorator concept that we have discussed on the mailing list. This change creates a new class (decl_decorator_t) that is used to decorate a decl with information later used by the creator in pyplusplus. This class does not change anything in pygccxml but allows users (and APIs) to inject information into the decls. - Currently allowed decorations: - renaming - finalizing - callPolicy - heldType - customCreators: - Additional information when finalize fails - Extended multiple file writer ---- [ User API: pypp_api ] --------- The API is available at: https://realityforge.vrsource.org/view/PyOpenSG/PyppApi Summary: This is a prototype user-level API for pyplusplus. The goals of the API are to provide an easy-to-use API that allows users to focus on the task of creating great boost.python wrappers. This API is designed to allow everything that Pyste has allowed and a great deal more. It strives to make the simple things simple and the hard things possible. It does this by wrapping the most common functionality of pyplusplus and pygccxml while still allowing access to the full power of the API. I will add more documentation later but for now here is a quick feature list and a few examples: Features: - Simplified interface to parser and configuration through a Module wrapper - paths, defines, caches, write methods, etc. - Lookup supporting regex for Namespace, Class, Method, Enum, Var - Direct interfaces for: - ignoring - exposing - renaming - held type - call policies - adding methods - method wrappers - adding custom text - adding custom creators - List based access to groups of declarations including - Declarations mathing same search - overloaded methods - typedef map for looking up expanded types from simple type names - templates: automatically creates template instantiation file to make gccxml "see" the template - Access to entire pygccxml declaration tree - Access to entire pyplusplus creator tree - powerful object oriented interface to allow complex structure generation scripts - A huge number of other things I can't remember right now... Examples: A simple example would look like: from pypp_api import * mod = Module(["header1.hpp","header2.hpp"] mod.parse() ns = mod.Namespace("test") ns.Class("MyClass").expose() mod.createModule("test", "output_dir") For a much more complex example take a look at [[https://realityforge.vrsource.org/viewcvs/trunk/src/generate_python_binding… generator]] -------------------------------- Please take a look and give me feedback. I thought Roman was going to be on vacation for a little longer so I was planning to clean up the code a little more before publicizing it but I have done my best to clean it up tonight. On a related note, I highly suggest that any users out there that have tried/used Pyste but have found it to be too lacking in power should really give pyplusplus a try. It has allowed me to do everything I ever wanted to do with Pyste and couldn't and then some. It is really a great tool and I can't thank Roman enough for taking the time to create it and make it available. -Allen

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Re: [C++-sig] deploying embedded python with additional package
by Nat Goodspeed Feb. 27, 2006

Feb. 27, 2006

> -----Original Message----- > From: c++-sig-bounces+ngoodspeed=solidworks.com(a)python.org [mailto:c++- > sig-bounces+ngoodspeed=solidworks.com(a)python.org] On Behalf Of Libor Vasa > Sent: Monday, February 27, 2006 1:38 PM > To: C++-sig(a)python.org > Subject: Re: [C++-sig] deploying embedded python with additional package > > >> I'm trying to build a C++ application that embedds Python and uses > >some > >> Python > >> package, that was installed to the system separately. Everything works > >> fine on > >> my machine, but I'm having difficulties deploying it elsewhere. I > >don't > >> want to > >> install neither python nor the additional library on the target > >machines, > >> is > >> there any way to do that? > > > I don't understand how py2exe can help, I don't need to convert a script > into an > executable, I need to deploy an executable, that uses Python/C API, and > depends > not only on Python, but also on some other packages (say Numeric). [Nat] Sorry -- I read your original message too quickly. Our app uses a Python script at top level, with all our C++ code imported as extension modules (or DLLs on which our extension modules depend). For that scenario, py2exe works pretty well. Its dependency analysis picks up the things that need to be packaged and brings them together into my dist subdirectory -- and the resulting image can be run on a target system without having to install any of those dependencies. I still find myself wanting to address your problem by taking advantage of the tool. I'm thinking that maybe you could construct a small Python script that imports everything you're going to need, except of course your top-level executable. You could run py2exe on that script to pull together all the relevant pieces, then discard the constructed .exe. You'd have to tell your own .exe to append the constructed library.zip file to your PYTHONPATH. Maybe there are better approaches specifically for the embedded case, but I don't know of any myself.

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Re: [C++-sig] deploying embedded python with additional package
by Libor Vasa Feb. 27, 2006

Feb. 27, 2006

>> -----Original Message----- >> From: c++-sig-bounces(a)python.org [mailto:c++-sig-bounces@python.org] >On >> Behalf Of Libor Vasa >> Sent: Monday, February 27, 2006 12:43 PM >> To: c++-sig(a)python.org >> Subject: [C++-sig] deploying embedded python with additional package >> >> I'm trying to build a C++ application that embedds Python and uses >some >> Python >> package, that was installed to the system separately. Everything works >> fine on >> my machine, but I'm having difficulties deploying it elsewhere. I >don't >> want to >> install neither python nor the additional library on the target >machines, >> is >> there any way to do that? > >[Nat] On a Windows machine, try using py2exe (http://www.py2exe.org/). >On a Mac, try using py2app (http://undefined.org/python/py2app.html). I don't understand how py2exe can help, I don't need to convert a script into an executable, I need to deploy an executable, that uses Python/C API, and depends not only on Python, but also on some other packages (say Numeric).

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pyplusplus: Feature requests
by Matthias Baas Feb. 27, 2006

Feb. 27, 2006

Hi, now that I have a working module that I can play around with, I came upon some stuff that I'd like to see in pyplusplus: - When keywords are disabled on a constructor any optional argument is turned into a non-optional argument. Pyste uses the optional<> construct to set optional values. It would be great if pyplusplus would do that as well, so that optional values are still optional even when keywords are not specified. So for example, if there's a constructor that takes 3 doubles from which two are optional, Pyste generates: .def(init< double, optional< double, double > >()) I haven't checked, but maybe this scheme even works with keyword arguments...? (which would solve the registration order problem for constructors) - Copy constructors don't get wrapped - Index operators don't get wrapped - Friend functions that implement operators for a class don't get wrapped (for example, if you have a 3D vector class and you implement the scalar multiplication with a float you need such a friend function if you also want to support the expression float*vec and not only vec*float). By the way, here I don't understand why I actually can multiply my vectors with an integer (even from both sides), but not with a float from the right side. The following are all the defs in my vector that deal with multiplication: MVector_exposer.def( bp::self * bp::self ); MVector_exposer.def( bp::self * bp::other< double >() ); MVector_exposer.def( bp::self * bp::other< MMatrix >() ); So why can I multiply my vector with an integer? (the C++ class does allow that but the stuff isn't wrapped) And if I try to multiply a float from the left side I get: TypeError: can't multiply sequence by non-int ?!? - When using a cache the order of enum values changes in the generated source files from call to call. This leads to new compilations that wouldn't be necessary. - Are there any plans on adding some support for creating wrapper methods in cases where they are absolutely necessary? Suppose you have a method void getSize(int& width, int& height) that returns the resolution of an image. pyplusplus currently wraps that method happily without issuing a warning, but I'm not even able to call that function from Python, let alone will it ever do what it's supposed to do. I don't expect pyplusplus to deal with such cases in a fully automated manner (as to date, reading the user's mind is still out of scope of such tools ;) but it could help the user resolve these things. A minimal aid would simply be to report such methods that might not work in Python so that the user knows he has to do something about it. Maybe for some cases we could provide some automatic wrapper generation once the user has specified which arguments are actually output values and shouldn't be part of the argument list in Python. - Matthias -

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Re: [C++-sig] deploying embedded python with additional package
by Nat Goodspeed Feb. 27, 2006

Feb. 27, 2006

> -----Original Message----- > From: c++-sig-bounces(a)python.org [mailto:c++-sig-bounces@python.org] On > Behalf Of Libor Vasa > Sent: Monday, February 27, 2006 12:43 PM > To: c++-sig(a)python.org > Subject: [C++-sig] deploying embedded python with additional package > > I'm trying to build a C++ application that embedds Python and uses some > Python > package, that was installed to the system separately. Everything works > fine on > my machine, but I'm having difficulties deploying it elsewhere. I don't > want to > install neither python nor the additional library on the target machines, > is > there any way to do that? [Nat] On a Windows machine, try using py2exe (http://www.py2exe.org/). On a Mac, try using py2app (http://undefined.org/python/py2app.html).

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