Norbert wrote:
Hello *, i am experimenting with threads and get puzzling results. Consider the following example: #-------------------- import threading, time
def threadfunction(): .....print "threadfunction: entered" .....x = 10 .....while x < 40: .........time.sleep(1) # time unit is seconds .........print "threadfunction x=%d" % x .........x += 10
print "start" th = threading.Thread(target = threadfunction()) th.start() print "start completed" #-------------------- (the dots are inserted becaus Google mangles the lines otherwise)
This program gives the following result : ---- start threadfunction: entered threadfunction x=10 threadfunction x=20 threadfunction x=30 start completed ---- My aim was that the main program should continue to run while threadfunction runs in parallel. That's the point of threads after all, isn't it ?
I awaited something like the following : start threadfunction: entered start completed <------------------- threadfunction x=10 threadfunction x=20 threadfunction x=30
Does anyone know what's going on here ?
Well, I don't believe there's any guarantee that a thread will get run preference over its starter - they're both threads, after all. Try putting a sleep after th.start() and before the print statement and you should see that the "worker" thread runs while the main thread sleeps.
The same would be true if each were making OS calls and so on. When everything is more or les continuous computation, and so short it can be over in microseconds, there's no motivation for the scheduler to stop one thread and start another.
regards Steve -- Steve Holden http://www.holdenweb.com/ Python Web Programming http://pydish.holdenweb.com/ Holden Web LLC +1 703 861 4237 +1 800 494 3119 -- http://mail.python.org/mailman/listinfo/python-list
