embedded python and windows multi threading, can't get it to work

[freesteel]

I am trying to run a python programme embedded from C++. I want to run
the same python code concurrently in several threads. I read the manual
on embedding, especially chapter 8, and searched for relevant info on
google all afternoon, but I can't get this to work. What am I doing
wrong? I use python2.4 and vc++7 (.net). The first thread seems to work
okay, the 2nd thread crashes, but the exception information is not very
useful:
(An unhandled exception of type 'System.NullRef erenceException '
occurred in pyembed_test.ex e

Additional information: Object reference not set to an instance of an
object.)

Here is a simplified example, it is heavily based on this article:
http://www.codeproject.com/cpp/embedpython_1.asp

#include <afxwin.h>
#include <Python.h>
#include <Windows.h>
#include <process.h>

#define USE_AFX 0


#if USE_AFX
UINT MyThread(LPVOID lpParam)
#else
void MyThread(void* lpParam)
#endif
{
Py_Initialize() ;
//#if 0
// PyEval_InitThre ads();
PyThreadState *mainthreadstat e = PyThreadState_G et();
PyInterpreterSt ate *maininterprete rstate = mainthreadstate->interp;
PyThreadState *mythreadstate =
PyThreadState_N ew(maininterpre terstate);
PyEval_ReleaseL ock();
PyEval_AcquireL ock();
PyThreadState *tmpstate = PyThreadState_S wap(mythreadsta te);
//#endif
int* num = (int *)lpParam;
int ret = 0;
ret = PyRun_SimpleStr ing("x = []");
ret = PyRun_SimpleStr ing("for i in range(10):\n x.append(i)");
char cmd[100];
sprintf(cmd, "f = open('test%d.tx t', 'w')", *num);
ret = PyRun_SimpleStr ing(cmd);
ret = PyRun_SimpleStr ing("f.write('% s' % x.__str__())");
ret = PyRun_SimpleStr ing("f.close()" );

//#if 0
PyThreadState_S wap(tmpstate);
PyEval_ReleaseL ock();
PyThreadState_C lear(mythreadst ate);
PyThreadState_D elete(mythreads tate);
//#endif

Py_Finalize();
#if USE_AFX
return 0;
#else
_endthread();
#endif
}

class CMyWinApp : public CWinApp
{
public:
CMyWinApp() { }
BOOL InitInstance()
{
int num0 = 0, num1 = 1;
HANDLE hnd0, hnd1;
#if USE_AFX
CWinThread* pThread0 = AfxBeginThread( MyThread, &num0);
hnd0 = pThread0->m_hThread;
CWinThread* pThread1 = AfxBeginThread( MyThread, &num1);
hnd1 = pThread1->m_hThread;
#else
hnd0 = (HANDLE) _beginthread(My Thread, 0, &num0);
hnd1 = (HANDLE) _beginthread(My Thread, 0, &num1);
#endif

// wait for the worker thread to terminate.
WaitForSingleOb ject(hnd0, INFINITE);
WaitForSingleOb ject(hnd1, INFINITE);

return TRUE;
};
};

CMyWinApp app;

[Serge Orlov]

freesteel wrote:

I am trying to run a python programme embedded from C++. I want to run
the same python code concurrently in several threads. I read the manual
on embedding, especially chapter 8, and searched for relevant info on
google all afternoon, but I can't get this to work. What am I doing
wrong? I use python2.4 and vc++7 (.net). The first thread seems to work
okay, the 2nd thread crashes, but the exception information is not very
useful:
(An unhandled exception of type 'System.NullRef erenceException '
occurred in pyembed_test.ex e

Running one iterpreter in more than one thread is not supported. You
need to create one interpreter per thread using Py_NewInterpret er
(don't forget to read "Bugs and caveats" paragraph). I hope you also
realize the interpreters won't share objects.