如何从IronPython方法返回值到C＃

Question

执行以下代码后

    _engine = Python.CreateEngine();
    var searchPaths = _engine.GetSearchPaths();
    searchPaths.Add(@"C:\Program Files (x86)\IronPython 2.7\Lib");
    _engine.SetSearchPaths(searchPaths);
    _scope = _engine.CreateScope();

    var pythonResult = _engine.Execute(

@"import sys
def testFunc():
    return 3"

    , _scope);

C＃变量pythonResult为null。我希望它等于我可以调用的返回3的东西。

我做错了什么？