can't delete from a dictionary in a loop

[castironpi]

On May 17, 3:06 am, George Sakkis <george.sak... at gmail.com> wrote:
> On May 16, 5:22 pm, "Dan Upton" <up... at virginia.edu> wrote:
>
>
>
>
>
> > This might be more information than necessary, but it's the best way I
> > can think of to describe the question without being too vague.
>
> > The task:
>
> > I have a list of processes (well, strings to execute said processes)
> > and I want to, roughly, keep some number N running at a time.  If one
> > terminates, I want to start the next one in the list, or otherwise,
> > just wait.
>
> > The attempted solution:
>
> > Using subprocess, I Popen the next executable in the list, and store
> > it in a dictionary, with keyed on the pid:
> > (outside the loop)
> > procs_dict={}
>
> > (inside a while loop)
> > process = Popen(benchmark_exstring[num_started], shell=true)
> > procs_dict[process.pid]=process
>
> > Then I sleep for a while, then loop through the dictionary to see
> > what's terminated.  For each one that has terminated, I decrement a
> > counter so I know how many to start next time, and then try to remove
> > the record from the dictionary (since there's no reason to keep
> > polling it since I know it's terminated).  Roughly:
>
> > for pid in procs_dict:
> >   if procs_dict[pid].poll() != None
> >    # do the counter updates
> >    del procs_dict[pid]
>
> Since you don't look up processes by pid, you don't need a dictionary
> here. A cleaner and efficient solution is use a deque to pop processes
> from one end and push them to the other if still alive, something like
> this:
>
> from collections import deque
>
> processes = deque()
> # start processes and put them in the queue
>
> while processes:
>     for i in xrange(len(processes)):
>         p = processes.pop()
>         if p.poll() is None: # not finished yet
>             processes.append_left(p)
>     time.sleep(5)
>
> HTH,
> George- Hide quoted text -
>
> - Show quoted text -

No underscore in appendleft.