Python 3 | Threading works weirdly -

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i'm learning python 3 , watched tutorial threading:

https://www.youtube.com/watch?v=waxk8g1hb_q&index=33&list=pl6gx4cwl9dgacbmi1sh6oamk4jhw91mc_#t=365.299172

i tested example code reason result sort of weird.

import threading  class messenger(threading.thread):     def run(self):         _ in range(10):             print(threading.currentthread().getname())   m1 = messenger(name="send messages") m2 = messenger(name="receive messages") m1.start() m2.start()

i expecting program print out "send messages" , "receive messages" on sort of random order, happened, , i'm not quite sure why:

send messagesreceive messages  send messagesreceive messages  send messagesreceive messages  send messagesreceive messages  send messagesreceive messages  send messagesreceive messages  send messagesreceive messages  send messagesreceive messages  send messagesreceive messages  send messagesreceive messages

can explain me why results printed way? given!

i ended getting different results when ran code snippet. situation happening cpu scheduling threads in "correct" order on run posted, produce different results if continue run multiple times. normal threading behavior, because cpu decides when each process gets run.

i make sure running exact code posted, because output separated new line characters while yours seems not be. 

send messages send messages receive messages send messages send messages send messages send messages receive messages receive messages send messages receive messages send messages receive messages send messages receive messages send messages receive messages receive messages receive messages receive messages

running code:

import threading  class messenger(threading.thread):     def run(self):         _ in range(10):             print(threading.currentthread().getname())   m1 = messenger(name="send messages") m2 = messenger(name="receive messages") m1.start() m2.start()

if read more:

https://www.cs.uic.edu/~jbell/coursenotes/operatingsystems/5_cpu_scheduling.html

the important part section on cpu scheduler:

  • whenever cpu becomes idle, job of cpu scheduler ( a.k.a. short-term scheduler ) select process ready queue run next.

  • the storage structure ready queue , algorithm used to
    select next process not fifo queue. there are
    several alternatives choose from, numerous adjustable
    parameters each algorithm, basic subject of this
    entire chapter.


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