[C++-sig] [c++-sig] How to raise a python exception in boost.python?

[甜瓜]

2007/6/6, 甜瓜 <littlesweetmelon at gmail.com>:
> I have read the python C API manual for exception handling. It seems
> that if the function below is called, python interpreter will get a
> ValueError exception,
> PyObject*  RaiseValueError(PyObject*)
> {
>     PyErr_SetString(PyExc_ValueError, "for some reason...");
>     return 0;
> }
> just like the statement in python:
> >>> raise ValueError("for some reason...")
> Is that right??
>
> Ok, but if I move this function into boost.python, the exception disappeared.
> object RaiseValueError(object)
> {
>     PyErr_SetString(PyExc_ValueError, "for some reason...");
>     return object();
> }
>
> If I throw a C++ exception, later on the boundary of boost.python, it
> will be translated into a python exception: (in boost file errors.cpp)
>
> BOOST_PYTHON_DECL bool handle_exception_impl(function0<void> f)
> {
>     try
>     {
>         if (detail::exception_handler::chain)
>             return detail::exception_handler::chain->handle(f);
>         f();
>         return false;
>     }
>     catch(const boost::python::error_already_set&)
>     {
>         // The python error reporting has already been handled.
>     }
>     catch(const std::bad_alloc&)
>     {
>         PyErr_NoMemory();
>     }
>     catch(const bad_numeric_cast& x)
>     {
>         PyErr_SetString(PyExc_OverflowError, x.what());
>     }
>     catch(const std::out_of_range& x)
>     {
>         PyErr_SetString(PyExc_IndexError, x.what());
>     }
>     catch(const std::exception& x)
>     {
>         PyErr_SetString(PyExc_RuntimeError, x.what());
>     }
>     catch(...)
>     {
>         PyErr_SetString(PyExc_RuntimeError, "unidentifiable C++ exception");
>     }
>     return true;
> }
>
> So, I'm really confused. Why does NOT my calling to PyErr_SetString
> work, while boost.python similar calling works? Does boost.python eats
> my error flags?
>
> Anyway, my goal is the raise a python exception (eg: ValueError) from
> boost.python based code. How to do that?  (Do not tell me to write a
> custom exception translator and plug it into boost.python... -_-!! The
> only thing I need is just to raise a python exception directly.)
>
> Thank you.
> ---
> ShenLei
>

Oh~~ I solved this problem by myself. I forgot to call
throw_error_already_set() to tell boost.python that python error has
occurred.  Sorry for such newbie mistake. ^_^

---
ShenLei