Python multithreaded print statements delayed until all threads complete execution

Question

I have a piece of code below that creates a few threads to perform a task, which works perfectly well on its own. However I'm struggling to understand why the print statements I call in my function do not execute until all threads complete and the print 'finished' statement is called. I would expect them to be called as the thread executes. Is there any simple way to accomplish this, and why does this work this way in the first place?

def func(param):     time.sleep(.25)     print param*2  if __name__ == '__main__':     print 'starting execution'     launchTime = time.clock()     params = range(10)     pool=multiprocessing.Pool(processes=100) #use N processes to download the data     _=pool.map(func,params)     print 'finished' 

Answer 1

For python 3 you can now use the flush param like that:

print('Your text', flush=True)

Answer 2

This happens due to stdout buffering. You still can flush the buffers:

import sys  print 'starting' sys.stdout.flush() 

You can find more info on this issue here and here.