On Thu, Sep 5, 2013, at 03:27 PM, Paul Pittlerson wrote: > I'm trying to understand data handling using multiprocessing and > threading, haven't gotten very far without running into problems. This is > my code:
[snip (not sure why you are using multiprocessing and threading at the same time] > What I expect to happen is the Debugger object will receive one string at > a time, and read it from the queue. But that's not what I see the the > output, the "started worker" stuff seems to print for every process, but > "ticked" and "exited" will show up in unpredictable ways, I'm guessing > they overwrite each other and therefore will not always appear in the > output. > > So I'm looking for help in trying to make sense of this kind of stuff, I > thought this was the basic functionality that Queue() would take care of > unless there is some other problem in my code. My output is probably totally different than your output. I only get the processes starting. Here's why: This stuff all runs asynchronously. When you start the "Debugger" thread.. I see you put a sleep() in it, but that guarantees nothing. At least on my machine which is somewhat loaded ATM, by the time the Processes are started, the Debugger thread has already finished (because of the check to see if the queue was empty). Apparently it is took longer than 1 second from the time the Debugger was started and the first Process was started. Likewise, what you are getting is probably a case where the queue is momentarily empty by the time the debugger loop gets ahold of the queue lock and checks to see if it's empty. Therefore the Debugger quits. Also because of the asynchronicity of processes, threads, you can not guarantee the order that the processes will get the opportunity to put() into the queue. Also you can't (and shouldn't) depend on the time that __del__ gets called. It can get called at any time, in any order and sometimes not at all.* Hope this helps. * http://docs.python.org/3/reference/datamodel.html?highlight=__del__#object.__del__ -- https://mail.python.org/mailman/listinfo/python-list
