How to suppress exception printing to console?

[Ulrich Eckhardt]

Am 01.06.2012 05:06, schrieb Qi:
> On 2012-5-31 23:01, Ulrich Eckhardt wrote:
>> I can only guess what you are doing, maybe you should provide a simple
>> piece of code (or, rather, one C++ piece and a Python piece) that
>> demonstrates the issue. What I could imagine is that the Python
>> interpreter shuts down with something it considers an unhandled
>> exception, which it then prints to stdout before exiting. When
>> embedding, that shouldn't happen from just calling a Python function in
>> a loaded script, those should just make the error available to the C++
>> side via PyErr functions etc.
> 
> 
> PyRun_SimpleString("SomeCppFunc(1, 2)");
> 
> SomeCppFunc is C++ function bound to Python, and in SomeCppFunc
> it detects the parameter mismatch (such as it expects the first
> parameter to be a string), it throws an exception.
> Then the C++ binding code catches the exception, and call
> PyErr_SetString to propagate it to Python.

I think this has nothing to do with the called C++ code, I guess the
same happens if you call PyRun_SimpleString("raise Exception()");.


> Then Python will print the error message to console.
> What I want to do is to suppress the error message printing...

Don't use PyRun_SimpleString() or catch the exception there. The point
is that it runs the whole string as a module, like running a script from
the commandline, and a pending exception on exit is then reported to stdout.

What I do here is that I create a module using the C API that I register
with Py_InitModule(). It contains the C++ functions exported to Python.
I then load a script using PyImport_ImportModule() and use
PyObject_GetAttrString(), PyCallable_Check() and PyObject_CallObject()
to run the main function of that script.


> Can I redirect sys.stdout in C++?

Maybe, I haven't tried. Since I require a proper main function in the
Python code anyway, I added a few more requirements, i.e. that it uses
one of the provided C++ functions for output. I think you can simply
assign "sys.stdout.write = log_string", where log_string is the provided
C++ function.

Uli