On Oct 15, 6:32 pm, MRAB <pyt...@mrabarnett.plus.com> wrote: > TerryP wrote: > > On Oct 15, 7:42 pm, Jeremy <jlcon...@gmail.com> wrote: > >> I need to write a Python script that will call some command line > >> programs (using os.system). I will have many such calls, but I want > >> to control when the calls are made. I won't know in advance how long > >> each program will run and I don't want to have 10 programs running > >> when I only have one or two processors. I want to run one at a time > >> (or two if I have two processors), wait until it's finished, and then > >> call the next one. > > >> How can I use Python to schedule these commands? > > >> Thanks, > >> Jeremy > > > External programs are not system calls; external programs are invoked > > through system calls; for example system() is a function call which > > when implemented under UNIX systems invokes some form of fork() and > > exec(), and likely spawn() under Windows NT. > > > If you want simple sequenceal execution of external programs, use a > > suitable blocking function to execute them (like system) combined with > > a simple loop over the sequence of commands to run. > > > for prog in ['cmd1', 'cmd2', 'cmd3']: > > os.system(prog) > > > blah. > > > For anything more detailed (or complex) in response, try being more > > detailed yourself ;). > > You could use multithreading: put the commands into a queue; start the > same number of worker threads as there are processors; each worker > thread repeatedly gets a command from the queue and then runs it using > os.system(); if a worker thread finds that the queue is empty when it > tries to get a command, then it terminates.
Yes, this is it. If I have a list of strings which are system commands, this seems like a more intelligent way of approaching it. My previous response will work, but won't take advantage of multiple cpus/cores in a machine without some manual manipulation. I like this idea. Thanks! Jeremy -- http://mail.python.org/mailman/listinfo/python-list
