Jupyter notebook carriage return not working

Question

I'm trying to print a progress bar using end=\r with print(), but the Jupyter notebook output still has new lines.

for i in range(0, 100000):
    print(i, end='\r')

Output:

I'm running the server on Ubuntu 18.04 and am accessing it using Chrome on a Mac. How can I make the carriage return work?

@trincot - with the '\r', each output should overwrite the previous. So the output should be `999999`. — Kingsley, Dec 16 '18 at 21:38
Possible duplicate: https://stackoverflow.com/q/42855972/190597 — unutbu, Dec 16 '18 at 21:43

Kingsley · Accepted Answer · 2018-12-16T22:00:45.047

There is nothing wrong with your code. Running in plain Ubuntu 18 / Python3 it behaves as expected.

I guess this is some kind of buffering issue (or a bug in Jupyter).

Based on the link @unutbu posted, it seems that only a minor time delay is needed to allow Jupyter to get its ship in shape.

import time
for i in range(100000):
    print(i, end='\r')
    time.sleep(0)  # EDIT, somehow even this works too.
print("")

Obviously if you really do have a huge amount of output (like 100k lines), this is far from ideal. But the real delay is in the flushing and re-painting of the screen, not the actual time.sleep().

If you are doing this sort of thing in a quick-repetition loop, it may be better to only update the progress-bar once every few seconds (or so). This can be accomplished by checking for a time delta.

@MarkMeyer - maybe add a `sys.stdout.flush()` after the print? Are you using Python3 ? — Kingsley, Dec 16 '18 at 22:08

Jupyter notebook carriage return not working

1 Answers1