[C++-sig] Returning None from __getitem__

[Stefan Seefeld]

Hi Renji,

 From a language / API design point of view, I think it would be best 
(i.e., least surprising) to follow the expected behavior. Python's dict 
type does have ways to handle what you want (and you can even set 
default values to be returned for non-existent keys).

As for your particular case, where your C++ map throws an exception, but 
you want the wrapper to return None, that's simple, too:

boost::python::object my_get_wrapper(PropSet &p, std::wstring const &k)
{
   try { return p->get(k);} // implicitly convert valid value to python 
object
   catch (InvalidKeyException const &) { return 
boost::python::object();} // on failure, return None
}

Then, you bind that as 'get':

class_<PropSet, ...> (...)
    .def("get", my_get_wrapper);


HTH,
       Stefan

-- 

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