How do I propagate C++ exceptions to Python in a SWIG wrapper library?

Question

I\'m writing a SWIG wrapper around a custom C++ library which defines its own C++ exception types. The library\'s exception types are richer and more specific than standard

Answer 1

I'll add a bit here, since the example given here now says that "%except(python)" is deprecated...

You can now (as of swig 1.3.40, anyhow) do totally generic, script-language-independent translation. My example would be:

%exception { 
    try {
        $action
    } catch (myException &e) {
        std::string s("myModule error: "), s2(e.what());
        s = s + s2;
        SWIG_exception(SWIG_RuntimeError, s.c_str());
    } catch (myOtherException &e) {
        std::string s("otherModule error: "), s2(e.what());
        s = s + s2;
        SWIG_exception(SWIG_RuntimeError, s.c_str());
    } catch (...) {
        SWIG_exception(SWIG_RuntimeError, "unknown exception");
    }
}

This will generate a RuntimeError exception in any supported scripting language, including Python, without getting python specific stuff in your other headers.

You need to put this before the calls that want this exception handling.