On Thu, 05 Jan 2006 17:15:20 -0500, Koncept <[EMAIL PROTECTED]> wrote: > >Hi. I am fairly new to Python programming and am having some trouble >wrapping my head around threading. >
It's pretty much the standard threading model. >This is a very basic example of what I am trying to do, and would >greatly appreciate having this code hacked to pieces so that I can >learn from you folks with experience. > >What I would like to learn from this example is how to use threads to >call on other classes and append/modify results in a list outside of >scope (basically keep track of variables throught the total threading >process and return them somehow afterwards ). I was thinking about >using some sort of global, but I am not sure what the best approach to >this is. Why would anyone want to learn that? What you want to do is learn how to *avoid* doing that :P Writing threaded programs that do anything other than allow individual threads to operate on an isolated chunk of input and return an isolated chunk of output is extremely difficult; perhaps even impossible. > >Thanks kindly for any assistance you may be able to offer. > >-- code -- > >import time, random, threading > >order = [] > >class Foo: > def __init__(self, person): > print "\nFoo() recieved %s\n" % person > >class Bar(threading.Thread, Foo): > def __init__(self, name): > threading.Thread.__init__(self, name = name) > self.curName = name > def run(self): > global order > sleepTime = random.randrange(1,6) > print "Starting thread for %s in %d seconds" % \ > (self.getName(), sleepTime) > time.sleep(sleepTime) > Foo.__init__(self,self.getName()) > print "%s's thread has completed" % self.getName() > order.append(self.getName()) Note that above you are sharing not only `order' between different threads (the append method of which is threadsafe, so this is nominally okay) and you are *also* sharing standard out, which is not safe to use in the manner you are using it. The program contains a subtle race condition which can cause output to be misformated. You need to change the print statements to single sys.stdout.write calls, or use a lock around any print. > >def main(): > for person in ['Bill','Jane','Steve','Sally','Kim']: > thread = Bar(person) > thread.start() To answer the question you asked, accumulate the threads in a list. After you have started them all, loop over the list calling join on each one. join will block until the thread's function returns. > > # How do I print "order" after all the threads are complete? > print "\nThreads were processed in the following order:" > for i, person in enumerate(order): print "%d. %s" % (i+1,person) > >if __name__ == "__main__": > main() > Jean-Paul -- http://mail.python.org/mailman/listinfo/python-list
