autoflush on/off

[Jabba Laci]

Hi,

I'd like to set autoflush on/off in my script. I have a loop that is
checking something and every 5 second I want to print a '.' (dot). I
do it with sys.stdout.write and since there is no newline, it is
buffered and not visible immediately. I have this solution to use
unbuffered output:

autoflush_on = False

def unbuffered():
"""Switch autoflush on."""
global autoflush_on
# reopen stdout file descriptor with write mode
# and 0 as the buffer size (unbuffered)
if not autoflush_on:
sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)
autoflush_on = True

I call unbuffered() once and it works well. However, when this loop is
over, I'd like to set the output back to buffered. How to do that? As
far as I remember, in Perl it was simply $| = 1 and $| = 0. Can it
also be switched back and forth in Python?

Thanks,

Laszlo

 

[Ulrich Eckhardt]

Am 04.02.2013 18:12, schrieb Jabba Laci:

autoflush_on = False

def unbuffered():
"""Switch autoflush on."""
global autoflush_on
# reopen stdout file descriptor with write mode
# and 0 as the buffer size (unbuffered)
if not autoflush_on:
sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)
autoflush_on = True

Note that you have two file objects (one not reachable any more) both
writing to the same file descriptor. This also means you should first
flush sys.stdout before changing it, otherwise it might still contain
unflushed data.

I call unbuffered() once and it works well. However, when this loop is
over, I'd like to set the output back to buffered. How to do that?

Just set sys.stdout back to the original value. OTOH, also check if you
can't tell sys.stdout not to buffer.

As far as I remember, in Perl it was simply $| = 1 and $| = 0.

"simply" ...


Uli

 

[garabik-news-2005-05]

Hi,

I'd like to set autoflush on/off in my script. I have a loop that is
checking something and every 5 second I want to print a '.' (dot). I
do it with sys.stdout.write and since there is no newline, it is
buffered and not visible immediately.

My solution is sys.stdout.write('.'); sys.stdout.flush()