Print without newline under function doesn't work as it should in Python

Question

I'm doing a progressbar for my uploading script and therefor i want to print a row of multiple '#' but i can't get it to work. When i tell Python to not add newline it does remove it but it doesn't work as expected under functions. Using "print ('#', end='')" in Python 3 or "print '#'," in Python 2 removes it but when executed under a functions it doesn't print anything out until the whole function is finished, it should not wait just like normal print.

import time

i = 0

def status():
    print('#', end='')

while i < 60:
    status()
    time.sleep(1)
    i += 1

This should print '#' every second but it doesn't. It prints them all after 60 seconds. Using just print('#') prints it out every second as expected. I really need a fix for this. Please help!

Solution: "sys.stdout.flush()" after each print :)

Why do you try to reinvent wheels? http://pypi.python.org/pypi/fish/ — Andreas Jung, Feb 24 '11 at 06:27
I use a solution based on [this](http://nadiana.com/animated-terminal-progress-bar-in-python) which is very cool, imo :) — simon, Feb 24 '11 at 06:54
Cool stuff. But my progressbar is actually a penis so my minimal solution works best :) — ggustafsson, Feb 24 '11 at 07:42

score 7 · Answer 1 · edited May 23 '17 at 10:27

7

You probably need to flush the output buffer after each print invocation. See How to flush output of Python print?

edited May 23 '17 at 10:27

Community

1
1

answered Feb 24 '11 at 06:26

ide

18,381
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score 1 · Accepted Answer · answered Jul 05 '21 at 21:25

Python is buffering the output until a newline (or until a certain size), meaning it won't print anything until the buffer gets a newline character \n. This is because printing is really costly in terms of performance, so it's better to fill a small buffer and only print once in a while instead.

If you want it to print immediately, you need to flush it manually. This can be done by setting the flush keyword argument to True.

import time

word = "One letter at a time"

for letter in word:
    print(letter, end='', flush=True)
    time.sleep(0.25)

score 0 · Answer 3 · edited Jun 08 '12 at 12:52

0

You can always use the strip() function.

edited Jun 08 '12 at 12:52

Tim Cooper

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answered Jun 07 '12 at 19:13

Jay

94
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score 0 · Answer 4 · answered Feb 24 '11 at 06:51

0

I tried your code in the IDLE for 2.5. So I had to use print format as - print '#',

Here is what I get when I execute it - The system prints '#' symbol every second. At the end of the loop I get the prompt back on the IDLE. So it seems to me that it is doing what you expect it to do.

Which version you are specifically using? Sorry I do not have version 3. So I cannot test it there.

answered Feb 24 '11 at 06:51

Sumod

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I've tried Python 2.6.1 and Python 3.2 in Terminal.app on OS X. – ggustafsson Feb 24 '11 at 06:59

Print without newline under function doesn't work as it should in Python

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