How to raise a python exception in boost.python?

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
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2007/6/6, Ìð¹Ï <littlesweetmelongmail.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
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