Converting the last example, that uses Python from multiple threads, is actually quite easy. All the hard work has already been done!

static void 
doWorkerThread( int threadNo )
{
    Interpreter interp ;
    for ( int i=0 ; i < 5 ; ++i )
    {
        BEGIN_PYTHON_INTERPRETER( interp )
        {
            // execute some Python
            stringstream buf ;
            buf << "print \"Thread " << threadNo << ": pass " << 1+i << "\"" ;
            Interpreter::runSimpleString( buf.str().c_str() ) ;
        }
        END_PYTHON_INTERPRETER()

        // sleep for a short time 
        Sleep( rand() % 100 ) ;
    }
}

We create an Interpreter object for each thread, and use an InterpreterLock object (managed by the BEGIN/END_PYTHON_INTERPRETER macros) to take care of swapping it in and out when we want to use it.

The only thing to be careful about here is that because we're in a worker thread, any exceptions that get thrown won't get caught by the main thread's catch handler; each worker thread needs its own try/catch block.

Download the source code here.

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