difference in printing to screen Mac / Windows

Tim Chase python.list at tim.thechases.com
Sat Jul 18 13:03:11 CEST 2009


> I notice a difference between running the following script on my Mac and on
> a PC:
> 
> from time import sleep
> for i in range(10):
>    print i,
>    sleep(2)
> 
> On my PC this prints a number every 2 seconds. This is the behavior I want.
> 
> On my Mac Python waits 10*2 = 20 seconds, and then prints 0 1 2 3 4 5 6 7 8
> 9

This sounds like a buffered vs. non-buffered output issue.  My 
guess would be that if you increased 10 to something larger, the 
output buffer would flush at various intervals.  The solution on 
the Mac (or other *nix-like OSes) would be to either start python 
in unbuffered mode:

   python -u mycode.py

Alternatively, you can force a flush of the output buffer at each 
iteration:

   import sys
   for i in range(10):
     print i
     sys.stdout.flush()
     sleep(2)

Lastly, you can force all standard-output in your program to be 
unbuffered without the "-u" parameter:

   sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)

Hope this helps,

-tkc





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