Stefan Seefeld wrote:
> On 03/04/2010 11:59 AM, Neal Becker wrote:
>> int main () {
>> Py_Initialize();
>>
>> object main_module = import("__main__");
>> object main_namespace = main_module.attr("__dict__");
>>
>> try {
>> object result = exec ("import sys\n"
>> "sys.path.append('./')\n"
>> "import test_embed\n"
>> "test_embed.five_square()\n",
>> main_namespace);
>> int five_squared = extract<int> (result);
>> std::cout<< five_squared<< '\n';
>> }
>> catch (error_already_set const&) {
>> PyErr_Print();
>> }
>> }
>>
>>
>> test_embed.py:
>> --------------------
>> def five_square ():
>> return 5 ** 2
>>
>> I get:
>> ./test_embed
>> TypeError: No registered converter was able to produce a C++ rvalue of
>> type int from this Python object of type NoneType
>>
>> Why did exec return None? I expected it to return the result of
>> "test_embed.five_squared()", which is the int 25. What is the meaning of
>> the return of exec_file? A python module can't return a result.
>>
>
> This is a straight wrapping of Python's C API. AFAICT, the return value
> is only useful to determine whether the call was successful. Thus, None
> may indicate an internal error, which you can check for with
> PyErr_Occured(). (I'm actually surprised we don't catch this internally
> and then raise an err_already_set exception !)
>
> The real error could be that the interpreter wasn't able to import one
> of the modules (wrong PYTHONPATH ?), or something similar.
>
> Regards,
> Stefan
>
That's strange, because docs for exec and exec_file claim to return object.
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