Sleeping and printing without newline?

Question

If I run this code:

for x in range(10):
    time.sleep(1)
    print("a")

It will do exactly what it should. But if I run this:

for x in range(10):
    time.sleep(1)
    print("a", end="")

It will wait the entire 10 seconds and then print the 10 a's.

How can I prevent this?

Definitely not a library bug. Always assume your own code is at fault first (it's seen a lot less testing). The problem is that [`stdout` is line-buffered](http://www.pixelbeat.org/programming/stdio_buffering/). — Jonathon Reinhart, Aug 02 '13 at 03:27
@JonathonReinhart that certainly seems logical, but this behavior seemed really eratic. Having to flush stdout certainly doesn't seem very "Python". They're probably very rare, but I have encountered bugs in the standard Python libraries before (zipfile in 2.6, apparently infamous) — tkbx, Aug 02 '13 at 03:30

score 8 · Accepted Answer · answered Aug 02 '13 at 03:25

Flush stdout after print.

import time
import sys

for x in range(10):
    time.sleep(1)
    print("a", end="")
    sys.stdout.flush()

Python 3.3 print function has optional flush parameter; You can write as follow in Python 3.3+.

import time

for x in range(10):
    time.sleep(1)
    print("a", end="", flush=True)

1 Answers1