[C++-sig] Howto wrap operator[]? (boost::python)

[Nicodemus]

Neal D. Becker wrote:

>I am playing with exposing std::vector<double>.  So far I got init OK, now I
>want to expose operator[].  I don't see anything in the tutorial about
>this.  Any hints?
>
>  
>

Currently you will have to expose them by hand. Python has two especial 
methods, named __setitem__ and __getitem__, that allows a class to 
define the behaviour of the [] operator. All you have to do is export 
this especial methods as members of your class. Here is some code 
(untested):

template <class T>
void vector_setitem(std::vector<T>& v, int index, T value)
{
    if (index >= 0 && index < v.size()) {
        v[index] = value;
    }
    else {
        PyErr_SetString(PyExc_IndexError, "index out of range");
        throw_error_already_set();
    }
}

template <class T>
T vector_getitem(std::vector<T> &v, int index)
{
    if (index >= 0 && index < v.size()) {
        return v[index];
    }
    else {
        PyErr_SetString(PyExc_IndexError, "index out of range");
        throw_error_already_set();
    }
}

BOOST_PYTHON_MODULE(std)
{
    class_<std::vector<double> >(...)
         ...
         .def("__getitem__", &vector_getitem)
         .def("__setitem__", &vector_setitem)
    ;
}