Delay/discrepancy between expected and actual output to iPython output

Question

I'm using the Enthought Canopy IDE to write Python and the the output of print commands do not reach the ipython output window at the time when I would expect them to. The clearest way to explain is to give an example:

import time

print 1
print 2
time.sleep(1)
print 3

for i in range(10):
    print i
    time.sleep(0.5)

The initial 1, 2 and 3 are displayed simultaneously after a second, and then there is a half second delay before the next 0 is displayed.

(as opposed to the expected instantaneous and simultaneous display of 1 and 2, then a 1 second delay before a simultaneous display of 3 and 0, then half second delays)

This is causing me issues as I am looking to get readouts of variables before a time consuming portion of script runs, and I cannot get it to display these readouts without terminating the program after calling the print command.

Any ideas/solutions?

I'm on Windows 7, let me know if you need any other specs/config details...

Thanks!

Answer 1

You can start the Python interpreter with an additional -u parameter, which gives you unbuffered output (i.e. instant). Or you can call sys.stdout.flush() after every print. Maybe even wrapping it in a function like this:

from __future__ import print_function
import sys

def print_flush(*args):
    print(*args)
    sys.stdout.flush()