Python sleep doesn't work right in a loop?

[Diez B. Roggisch]

ritterhaus at yahoo.com wrote:

> Just a simple bit of code to toggle between two state at intervals...
> 
> import time
> for i in range(4):
>     print 'On'
>     time.sleep(1)
>     print 'Off'
>     time.sleep(1)
> 
> ... SHOULD toggle On and Off four times with one-second pauses. When I
> run this, the loop pauses the full eight seconds then prints the Ons
> and Offs all at once. What's up with that?

Works for me - on a terminal using linux. BUT what not works is this:

python /tmp/test.py | cat

(test.py contains your code of course) The reason is buffered pipes being
used. Try this:

import time, sys
for i in range(4):
    print 'On'
    sys.stdout.flush()
    time.sleep(1)
    print 'Off'
    sys.stdout.flush()    
    time.sleep(1)

-- 
Regards,

Diez B. Roggisch