Mailman 3 January 2005 - Cplusplus-sig

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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what happened with this std::string parameter in boost.python
by Donnie Leen April 4, 2005

April 4, 2005

I made a program embedding boost.python, writting a module as following: void write( std::string s ) { // do nothing } BOOST_PYTHON_MODULE(mym) { def( "write", &write ); } I run the python code: import mym s = 'hello' mym.write(s) it runs ok, but if i run the python code as following: import mym s = int.__doc__ mym.write(s) it crashed, and it seems to crashed while boost.python try to delete the parameter s. Can someone tell me what happened to it? Thanks first. Donnie Leen

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Making copy of function derived from C++ pure virtual function
by Paul F. Kunz March 22, 2005

March 22, 2005

I have a function written in Python derived from C++. Now I want to clone this function in C++. What should I do in the copy constructor of the function wrapper? I have... FunctionWrap:: FunctionWrap ( const FunctionWrap & wrap ) : FunctionBase ( wrap ), m_self ( wrap.m_self ) { // what should be here to create a new PyObject that is copy of old one? } FunctionBase * FunctionWrap:: clone () const { return new FunctionWrap ( *this ); }

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Re: [C++-sig] Re: a working example of wrapping an instantiated c++ object
by Yao Heling March 16, 2005

March 16, 2005

Ok, I'll try to write a small tutorial for this. I'll post it here when it's ready. Thanks for your help, Joseph __________________________________ Do you Yahoo!? The all-new My Yahoo! - What will yours do? http://my.yahoo.com

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Wrapping C++ class with unnamed union
by Kevin Vance Feb. 11, 2005

Feb. 11, 2005

Hi, I am new to boost.python, so there may be a very simple answer to this. I would like to access the OGRE graphics library from python. But it has several classes with data like this: union { struct { Real r,g,b,a; }; Real val[4]; }; And I cannot access e.g. 'r' with a statement like: .def_readwrite("r", &Ogre::ColourValue::r) I'm assuming this is because there is an unnamed union and unnamed struct in between the class and the 'r'. I could write a new C++ class to wrap this one, and then use boost to wrap *that*. But if there is a simpler way, I would rather use it. Thanks for your advice, kvance

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virtual functions returning const char
by Aaron Bentley Jan. 31, 2005

Jan. 31, 2005

I've encountered a problem wrapping virtual functions that return const char *. I get ReferenceError: Attempt to return dangling pointer to object of type: c Here's my example code (adapted from the tutorial): struct Base { virtual const char * f(){return "fee";} }; struct BaseWrap: Base { BaseWrap(PyObject* self_) : self(self_){} const char *f() { return call_method<const char *>(self, "f"); } const char *default_f() {return Base::f();} PyObject *self; }; const char *call_f(Base &b) { return b.f(); } And then in the BOOST_PYTHON_MODULE class_<Base, BaseWrap, boost::noncopyable>("Base") .def("f", &Base::f, &BaseWrap::default_f) ; def ("call_f", call_f); Finally, in Python: class Derived(Base): def f(self): return "foo" d = Derived() assert(d.f() == "foo") assert(call_f(d) == "foo") b = Base() assert(b.f() == "fee") assert(call_f(b) == "fee") assert(Base().f() == "fee") b = Base() #all lines except this one pass assert(call_f(b) == "fee") All assertions except the last one pass. That is they pass 1. If I'm calling from Python or 2. If the default virtual function is not invoked. But if I invoke the default virtual function from C++, I get the dangling pointer exception. I don't really understand the problem, since string literals like "fee" should have a permanent location in memory. Aaron -- Aaron Bentley Director of Technology Panometrics, Inc.

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Iteration over an enumerated type
by Colin Irwin Jan. 27, 2005

Jan. 27, 2005

Hi, One feature that I've occasionally used in C++ is to iterate over all types of an enumerated type. This being possible if one defines the suitable increment (or decrement) operator. So in other words if one had the following enumerated type: enum KnownValue { Value1, Value 2, Value3, }; then the following code could be used, assuming that the increment operator is defined for the enumerated type: for ( KnownValue v = value1; v <= Value3; v++ ) { // ... } I now have a need to do the same thing in Python, with an enumerated type translated from C++. How does one do this? Assuming the enumerated type is translated directly across from C++ into Python (into the module my_module), then I'm been able to do: begin = my_module.KnownValue.Value1 end = my_module.KnownValue.Value3 for v in range( start, end ): # ... I'm far from being an expert in Python, but this has the immediate problem that the range function needs a type one beyond Value3 for the loop to iterate over all useable types. (Indeed, this can also be required in C++ depending on how the loop is written.) I was wondering whether there is a better way to do this in Python, without having to add the extra type? Would it make sense to provide 'begin' and 'end' functions (an extra type to indicate the end would be required, but given I'm talking about providing begin and end functions, then why not)? These could be available in the module, such that the above for loop would look like: for v in range( my_module.KnownValue.begin(), my_module.KnownValue.end() ): # ... Writing this example out, I would be quite happy with this solution, but does anyone have any other suggestions or experiences? Colin

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Conversion between boost::tuple and a python tuple
by Colin Irwin Jan. 26, 2005

Jan. 26, 2005

Hi, I have an interface in C++ for which I would like a binding into Python. In particular, one of the functions in the interface takes a boost::tuple argument, e.g.: class ExampleClass { public: ... void foo( boost::tuple<int, int, int> int_tuple ); }; I would like to (at least I think I would like to) reflect this into Python such that a user passes in a Python tuple. How would one achieve this? I've searched the BPL documentation and can't seem to find anything. I've also searched the relevant newsgroups and there are some old references (circa 2002) on how to achieve this, but this was with the v1 of the library, so I don't think the ideas/methods are applicable. Finally, is this a good idea? By this I mean, would it be a better idea to change the foo function signature to accept something like a std::vector and then employ an rvalue converter? I realise by doing this the intent of the interface is now a little different, i.e., with above, the user must pass a tuple of 3 values, whilst using a std::vector could lead to any number of integers passed into the function. However, this would make more sense from the Python side and I suspect would be easy (easier?) to code up - some of what I can imagine to be difficulties could result from a mismatch in the python tuple vs. boost::tuple semantics. All help would be much appreciated. The BPL is perfect for what I would like to do, however, I feel I'm lacking a bit of understanding. Colin

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where to store pyd files
by Olivier Ravard Jan. 26, 2005

Jan. 26, 2005

Hi, When the compilation is done, the .pyd file created is strored in the boost tree. Is there a way to say to bjam to store the .pyd file in another directiry ? Thanks. O.R.

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import function execution
by Olivier Ravard Jan. 25, 2005

Jan. 25, 2005

Hi, How to define a C++ function that will be executed automaticaly when the module is imported ? Thanks. O.R.

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