run function in separate process

[malkarouri at gmail.com]

After playing with Alex's implementation, and adding some support for
exceptions, this is what I came up with. I hope I am not getting too
clever for my needs:

import os, cPickle
def run_in_separate_process_2(f, *args, **kwds):
    pread, pwrite = os.pipe()
    pid = os.fork()
    if pid > 0:
        os.close(pwrite)
        with os.fdopen(pread, 'rb') as f:
            status, result = cPickle.load(f)
        os.waitpid(pid, 0)
        if status == 0:
            return result
        else:
            raise result
    else:
        os.close(pread)
        try:
            result = f(*args, **kwds)
            status = 0
        except Exception, exc:
            result = exc
            status = 1
        with os.fdopen(pwrite, 'wb') as f:
            try:
                cPickle.dump((status,result), f,
cPickle.HIGHEST_PROTOCOL)
            except cPickle.PicklingError, exc:
                cPickle.dump((2,exc), f, cPickle.HIGHEST_PROTOCOL)
        f.close()
        os._exit(0)



Basically, the function is called in the child process, and a status
code is returned in addition to the result. The status is 0 if the
function returns normally, 1 if it raises an exception, and 2 if the
result is unpicklable. Some cases are deliberately not handled, like a
SystemExit or a KeyboardInterrupt show up as EOF errors in the
unpickling in the parent. Some cases are inadvertently not handled,
these are called bugs. And the original exception trace is lost. Any
comments?

Regards,

Muhammad Alkarouri