Thanks Taner and J. Michael Owen. I have a lot to digest from your contributions. The contributions help, but will require some work from me to make them suitable for applying to pybindgen.
This issue can be tracked by a bug report from now on, to avoid spamming this list with details: https://bugs.launchpad.net/pybindgen/+bug/384488 2009/6/19 J. Michael Owen <mikeo...@llnl.gov> > Hello Gustavo and Taner, > Sorry I didn't follow up on this earlier with you guys -- I've been on > travel for a while since I started looking at pybindgen and just returned. > After Gustavo pointed out the python documentation for the sequence method > slots, I thought I would take a look at modifying pybindgen to allow me to > fill in the sequence slots for CppClass much like the numeric operator slots > are handled. I've been able to do this, and am attaching some modified > pybindgen source to this message for your perusal. With these modifications > I can pretty easily expose std::vector so that length, get and set item > (index access), and iteration work. I'll fill in more methods as needed, > but this is a start. > > I took this tack 'cause in my code I have C++ objects that naturally obey > both numeric object protocols (such as +, -, etc) as well as sequence > methods, and I need to reflect those operations into python. I want them to > look like python objects as much as possible, so it's nice to be able to use > [] rather than () for indexing for instance (it's best not to confuse your > users more than necessary). :) > > The way I have this working is if the user adds any of the following > methods to a CppClass ("__len__", "__getitem__", "__setitem__"), then the > corresponding slots in the sequence object protocols are filled in in using > those methods. I think this is fairly natural, since this is how you add > sequence methods to an object you define in python natively. > > With my modifications I can add a container as a cppclass like so: > > mod = Module("example") > mod.add_include("<vector>") > mod.add_include('"example.hh"') > std = mod.add_cpp_namespace("std") > vecint = std.add_class("vector", template_parameters=["int"], > custom_template_class_name="vector_of_int") > vecint.add_constructor([]) > vecint.add_constructor([param("int", "size")]) > vecint.add_constructor([param("int", "size"), param("int", "value")]) > vecint.add_method("size", "int", [], custom_name = "__len__") > vecint.add_function_as_method("indexContainer", "int", > [param("std::vector<int>", "self"), > param("int", > "index")], > template_parameters = ["std::vector<int>"], > custom_name = "__getitem__") > vecint.add_function_as_method("assignToPosition", None, > [param("std::vector<int>", "self"), > param("int", > "index"), > param("int", > "value")], > template_parameters = ["std::vector<int>"], > custom_name = "__setitem__") > vecint.add_method("push_back", None, [param("int", "value")], > custom_name="append") > > where "example.hh" contains a few helper methods: > > #include <stdexcept> > > namespace std { > > > //------------------------------------------------------------------------------ > // Extract a value from a container. > > //------------------------------------------------------------------------------ > template<typename Container> > inline > typename Container::value_type& > indexContainer(Container& container, > const size_t index) { > try { > return container.at(index); > } catch (out_of_range) { > PyErr_SetString(PyExc_IndexError, "Container index out of range"); > } > } > > > //------------------------------------------------------------------------------ > // Assign to a postion in a container. > > //------------------------------------------------------------------------------ > template<typename Container> > inline > void > assignToPosition(Container& container, > const size_t index, > const typename Container::value_type& value) { > if (index >= container.size()) { > PyErr_SetString(PyExc_IndexError, "Container index out of range"); > } else { > container[index] = value; > } > } > > } > > And the resulting vector<int> can be used from python kind of like you > would naturally expect: > > alastor1{owen}77: python > Python 2.6.1 (r261:67515, Jun 2 2009, 15:40:32) > [GCC 4.3.2 20081007 (Red Hat 4.3.2-7)] on linux2 > Type "help", "copyright", "credits" or "license" for more information. > >>> import example > >>> v = example.std.vector_of_int(20, 5) > >>> len(v) > 20 > >>> [x for x in v] > [5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5] > >>> v[10] = 100 > >>> [x for x in v] > [5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 100, 5, 5, 5, 5, 5, 5, 5, 5, 5] > >>> > > In this process I've also made a few other modifications to pybindgen: > > 1. In CppClass I've generalized the binary_numeric_operators to allow the > user to specify python types as one of the arguments. I needed to do this > so I could allow types to define "*" with a python float for instance, > rather than only allowing operators with other CppClass wrapped objects. > > 2. I've also added inplace_numeric_operators as an option for CppClass, > which fills in the appropriate slots in the number methods struct. > > 3. I added name mangling for template arguments, since some of my template > arguments for methods are themselves templates (such as in the example > above). > > The changes I have are made against pybindgen-0.10.0, and you should > compare the files in this tarball to that version. I'm no Python C-API > whiz, so I won't claim these are the most optimal ways to handle these > extensions to pybindgen, but it does work and passes all of pybindgen's > internal tests. I'm continuing to look at how I have to modify pybindgen in > order to meet the needs of wrapping my code, but I don't want to wander too > far afield of the mainline release! If these kinds of mods are not going to > work for want you want to do Gustavo, please let me know! Anyway, check out > these mods as you can and let me know what you think. > > Mike. > > > > On Jun 5, 2009, at 10:00 AM, Gustavo Carneiro wrote: > > > > 2009/6/5 J. Michael Owen <mikeo...@llnl.gov> > >> Hi Taner, >> Thanks for the suggestion! I actually was trying the same solution, >> except I wasn't sure how to handle the iterators. I'll try it out as you do >> in your example -- are you able to iterate over the vector in python the >> usual way? As in "for x in vec:"? >> >> Two curious things I noted about wrapping "std::vector" myself: >> >> 1. I can't seem to get indexing access to work, even though I wrap an >> indexing operation with the python name "__getitem__" >> >> 2. I also can't get python's len function to work, even if I provide >> "__len__" as follows: >> veci.add_method("size", "int", [], custom_name="__len__") >> >> Have you been able to make either of those methods work? >> > > It won't work because those are special methods in C/C++ side; Python > extension types use a "slots" mechanism for this kind of thing, see http:// > www. > python.org/doc/2.6/c-api/typeobj.html<http://+www.+python.org/doc/2.6/c-api/typeobj.html> > > >> >> Thanks! >> >> Mike. >> >> -- > Gustavo J. A. M. Carneiro > INESC Porto, Telecommunications and Multimedia Unit > "The universe is always one step beyond logic." -- Frank Herbert > > > > -- 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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