[C++-sig] how t o specify and/or update global dictionary for bp::call call

[Stefan Seefeld]

Gennadiy Rozental wrote:
> Hi,
>
> I've got class implemented in python, inherited from C++ class. I am using
> wrapper/get_overload to invoke it's methods:
>
> bp::override o = this->get_override( "update" );
> bp::call< void >( o.ptr(), arg1, arg2 );
>
> Now in update method I need to refer to the function foo that reside 
> in module moo.
>
> I've tried to add 
> from moo import foo
> and 
> from moo import *
>
> before class definition:
>
> class MyPyDerivedClass( MyCPPBase ):
>     def update( s, arg1, ARG2 ):
>         foo()
>
> Both attempts were futile. Looks like global dictionary during update call does
> not contain foo.
>   

For avoidance of doubt: you are saying the import itself was successful, 
but there was no 'foo' symbol in the global namespace after that point ?
I just modified the exec.cpp test (libs/python/tests/exec.cpp), and it 
all works like a charm.
(For reference: go to libs/python/tests/exec.cpp and modify the 
'exec_test' function to simulate what you want. Here is the modified 
script I use:

  python::object main = python::import("__main__");
  python::object global(main.attr("__dict__"));
  python::object result = python::exec(
    "from embedded_hello import *        \n"
    "from sys import *                   \n"                             
//<-- added just to show how to populate the global namespace of the script
    "class PythonDerived(Base):          \n"
    "    def hello(self):                \n"
    "        print platform         \n"                                 
//<-- use it
    "        return 'Hello from Python!' \n",
    global, global);

  python::object PythonDerived = global["PythonDerived"];
  python::object py_base = PythonDerived();
  Base& py = python::extract<Base&>(py_base);
  assert(py.hello() == "Hello from Python!");

> P.S. solution to add import method inside update method is unacceptable for
> various (mostly political) reasons, though it obviously will work. I definitely
> need this outside class definition
>
> P.P.S. Instance of class MyPyDerivedClass is created on C++ side based on
> pre-cached python type:
>
> cpp_derived = m_py_type();
>   

Sounds like what you are doing is very similar to what the test I just 
exerimented with does. Right ?


HTH,
       Stefan



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