Embedded Threading Question

[Tim Dietz]

Thorsten Goertz <thorsten at goertz.com> wrote in message news:<3DCADE0D.2E06C5E3 at goertz.com>...
> Tim Dietz wrote:
> 
> > When I test the module within the Python interpreter from
> > DOS, it's happy as a clam.  But, the problem is that when I
> > include the exact same module within the application, the
> > app hangs forever and I have to kill the process.
> 

Sorry it's taken me so long to reply.  I was put on a different
part of the project.  Now I'm back, but I still do not know how
to proceed.  Here is my situation again and some sample code.

I have a C++ GUI application that essentially provides a memo to
emulate the Python command line (>>>).  STDOUT is redirected to a
memo in a different window.  Upon initialization, there is no
support for Python threads--none was needed until now.  Now, we
are importing a file that creates and starts a thread that will
continue executing during the life of the application.  And,
actually, the thread works very well, until I try to call a C
function from Python.  That's when the application hangs.  If
I do not try to interact with C from this new Python thread,
the application is happy.  I can call these same C functions
from the main thread in Python, but not from a thread other than
main.  I am using python22.dll.

>From what I've read (in 'Embedding Python in Multi-Threaded C/C++
Applications'), I kind of understand about thread initialization,
and acquiring and releasing the lock while executing python statements.

My question is, do I need to wrap every single grouping of Py*()
function calls within an acquire/release lock pair, or are there
special calls that I should target.  I'm asking this, because the
Py*() calls are dispersed throughout a few files and I'm not sure
how to go about coding these so that I can have threads in my
Python code work.

A sample of the main init code follows (Borland C++Builder 3):

    Py_Initialize();

    PySys_SetArgv(_argc, _argv); // let Python see Borlandish args to Cntlr

    // Add our own script directory to the module search path
    if (PyRun_SimpleString("import sys"))
        return;
    cmd = String("sys.path.insert(0, '") +
                 AUTOLOAD_SCRIPT_DIR +
                 "')" ;
    if (PyRun_SimpleString(cmd.c_str()))
        return;

    // Autoload our primitives that are defined in Python.
    // Exec, not import, these so that they
    // are available in main namespace.
    cmd = String("execfile('") + 
        AUTOLOAD_SCRIPT_DIR + "\\\\" +
        AUTOLOAD_PRIMS_FILE + "')";
    if (PyRun_SimpleString(cmd.c_str()))
        return;

... then, in the destructor for this class, we only have
    the following statement...

    Py_Finalize();