start function in new process
Hello all, I would like to run a python function completely in a new process. For example I have a parent process. That parent process needs to start a child process in which the function is called. After the child process is finished however I want that the child process should stop and then only the parent process remain. When I start the function I want to pass arguments also which include a function reference. I tried os.fork() as I need to write it in linux. However it seems like the child process remain alive. I discovered this when I loop through the function. I see that the child process continue with the loop and starts again a new grand child untill the loop is finished. See code snippet. f() is the function I want to run in a new process. It got as one of the input a refence to a function c(). Function g() I called in a loop for 3 times. Now it seems that when child process get started in the function g() it return to the loop and it calls g() itself and starts itself a nwe child process. I do not want thant. I want the child process to perform the function f() and just finished. Does anyone know how I can achieve this ? def c(): print "function c" def f(a,b, d): # function I want to run in a new child process print a, b d() def g(): pidID = os.fork() if pidID == 0: # child do something here f(2,3,c) else: # parent do something here print "Parent for i in range(3): g() -- http://mail.python.org/mailman/listinfo/python-list
Re: start function in new process
On 5 mrt, 20:40, "Martin P. Hellwig" wrote: > On 03/05/10 19:21, wongjoek...@yahoo.com wrote: > > Any specific reason why threading.Thread or multiprocessing is not > suitable to solve your problem? > > -- > mph Because I got a memory leak in my function f(). It uses scipy, numpy, pylab, and I am not planning to solve the memory leak because its too complicated. So I thought of just calling the function then when it is finished the process is gone and all memory is released. With threading I don't think I would solve this problem. I am not sure though. -- http://mail.python.org/mailman/listinfo/python-list
Re: start function in new process
On 5 mrt, 21:02, "Martin P. Hellwig" wrote: > On 03/05/10 19:45, wongjoek...@yahoo.com wrote: > > > > > On 5 mrt, 20:40, "Martin P. Hellwig" > > wrote: > >> On 03/05/10 19:21, wongjoek...@yahoo.com wrote: > >> > >> Any specific reason why threading.Thread or multiprocessing is not > >> suitable to solve your problem? > > >> -- > >> mph > > > Because I got a memory leak in my function f(). It uses scipy, numpy, > > pylab, and I am not planning to solve the memory leak because its too > > complicated. So I thought of just calling the function then when it is > > finished the process is gone and all memory is released. With > > threading I don't think I would solve this problem. I am not sure > > though. > > I would be surprised if you can't do the same with > subprocess/multiprocessing, since you seem to know how to identify the > memory leak it shouldn't be a problem scripting out a test to see if it > works this way. I would be interested though in your findings. > > -- > mph I can't use multiprocessing module since it comes only with python 2.6 and I am bound to python2.4. But subprocess does exist in python2.4, but the question now is, how do I achieve that ? Any example ? -- http://mail.python.org/mailman/listinfo/python-list
Re: start function in new process
On 5 mrt, 21:40, "Martin P. Hellwig" wrote: > On 03/05/10 20:09, wongjoek...@yahoo.com wrote: > > > > > On 5 mrt, 21:02, "Martin P. Hellwig" > > wrote: > >> On 03/05/10 19:45, wongjoek...@yahoo.com wrote: > > >>> On 5 mrt, 20:40, "Martin P. Hellwig" > >>> wrote: > >>>> On 03/05/10 19:21, wongjoek...@yahoo.com wrote: > >>>> > >>>> Any specific reason why threading.Thread or multiprocessing is not > >>>> suitable to solve your problem? > > >>>> -- > >>>> mph > > >>> Because I got a memory leak in my function f(). It uses scipy, numpy, > >>> pylab, and I am not planning to solve the memory leak because its too > >>> complicated. So I thought of just calling the function then when it is > >>> finished the process is gone and all memory is released. With > >>> threading I don't think I would solve this problem. I am not sure > >>> though. > > >> I would be surprised if you can't do the same with > >> subprocess/multiprocessing, since you seem to know how to identify the > >> memory leak it shouldn't be a problem scripting out a test to see if it > >> works this way. I would be interested though in your findings. > > >> -- > >> mph > > > I can't use multiprocessing module since it comes only with python 2.6 > > and I am bound to python2.4. But subprocess does exist in python2.4, > > but the question now is, how do I achieve that ? Any example ? > > Sure, for example if I want to check the openssl version (didn't specify > I need to provide a useful example :-) > > I would normally do on the command line: > [mar...@aspire8930 /usr/home/martin/Desktop]$ /usr/bin/openssl version > OpenSSL 0.9.8k 25 Mar 2009 > > The python subprocess equivalent is: > [mar...@aspire8930 /usr/home/martin/Desktop]$ python > Python 2.6.4 (r264:75706, Jan 31 2010, 20:52:16) > [GCC 4.2.1 20070719 [FreeBSD]] on freebsd8 > Type "help", "copyright", "credits" or "license" for more information. > >>> import subprocess as _sp > >>> ssl_version = _sp.Popen(['/usr/bin/openssl', 'version'], > stdout=_sp.PIPE) > >>> print(ssl_version.stdout.readlines()) > ['OpenSSL 0.9.8k 25 Mar 2009\n'] > >>> quit() > [mar...@aspire8930 /usr/home/martin/Desktop]$ > > If you get any error in the Popen part, you probably did not use the > full path or an illegal parameter. > > If you get a long wait in the readlines part, this usually means that > there is either nothing written to stdout or something is still being > written (I am not sure about this part though, it has been a while). > > hth > -- > mph Yes, I saw this example also before. HOwever what I want is to call an internal function which gets a reference of another internal function as input and not calling an external program. Do you have any example on that with subprocess module ? Thanks. -- http://mail.python.org/mailman/listinfo/python-list
